Impact of Bariatric Surgery on Pregnancy: A Systematic Review and Meta-analysis 

Impact of Bariatric Surgery on Pregnancy: A Systematic Review and Meta-analysis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Impact of Bariatric Surgery on Pregnancy: A Systematic Review and Meta-analysis Stergios Bobotis, Kendra Wilson, Abdul Rafay, Christopher Namgoong, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8723438/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Introduction: Bariatric surgery (BS) is an increasingly common intervention for women of reproductive age with morbid obesity, however the optimal timing of pregnancy following surgery has not yet been fully established, particularly as it impacts both obstetric and neonatal outcomes. Methods: Systematic search of Medline, EMBASE, EMCARE, and Cochrane databases identified 2468 studies for screening; 129 met inclusion criteria. The meta-analysis included women who underwent various BS procedures followed by pregnancy. Outcomes were analyzed using a random-effects model, comparing early (12 months) post-surgery conception. Maternal outcomes included gestational weight gain (GWG), gestational diabetes (GDM), pre-eclampsia, preterm birth, caesarean delivery, induction of labour, postpartum hemorrhage (PPH), anaemia, and internal hernia. Neonatal outcomes included Apgar scores, birthweight, gestational age, Neonatal intensive care unit (NICU) admissions, macrosomia, intrauterine growth restriction (IUGR), and perinatal death. Results: Bariatric surgery reduced pre-pregnancy BMI by 14 kg/m² (95% CI: 13– 15kg/m 2 , I² = 93.1%, p=0.000). Postoperative pregnancies had lower odds of gestational diabetes (OR 0.67, 95% CI: 0.53–0.85), pre-eclampsia (OR 0.60, 95% CI: 0.45–0.79), and macrosomia (OR 0.35, 95% CI: 0.24–0.50), but higher odds of intrauterine growth restriction (OR 2.09, 95% CI: 1.92–2.27), prematurity (OR 1.24, 95% CI: 1.04-1.47) and NICU admission (OR 1.39, 95% CI: 1.17–1.65). Mean GWG in women who conceived within 12 months of BS was 5.2kg (95% CI: 2.0, 8.0), compared to 10.2 (95% CI: 9.5, 11,1) in women who conceived >12 months after BS. PPH and caesarean rates were similar between post-BS pregnancies and obese controls. The prevalence rate of anaemia was 26% (95% CI: 22–31) and Vitamin D deficiency was 69.0% (95% CI: 61.8, 76.2). Conclusion: Bariatric surgery reduces obstetric risks of GDM, hypertensive disorders, and macrosomia. However, conception within 12 months is associated with lower GWG. BS increased odds of IUGR and preterm birth without significant difference in peri-natal mortality. Nutritional deficiencies, including anaemia, and fat-soluble vitamins, require close monitoring, particularly in early post-surgical pregnancies. Pregnancy peripartum perinatal maternal gestational postpartum postnatal antenatal neonate neonatal newborn baby babies foetal outcomes bariatric surgery weight loss surgery obesity gastric bypass sleeve gastrectomy Roux-en-Y laparoscopic bypass risks Figures Figure 1 Background Maternal obesity, defined as a pre-pregnancy body mass index (BMI) of ≥ 30 kg/m², presents significant risks for both mother and foetus ( 1 , 2 ). Despite growing awareness, maternal obesity has reached epidemic proportions, with prevalence rates of 31.9% in the United States, 21.3% in the United Kingdom, and similar increasing trends across Europe ( 2 – 4 ). During pregnancy, physiological insulin resistance increases due to placental secretion of diabetogenic hormones, including growth hormone, corticotropin-releasing hormone, placental lactogen, and prolactin, predisposing women to gestational diabetes mellitus (GDM) ( 5 , 6 ). Obese women experience a more pronounced decline in insulin sensitivity than those with normal weight, leading to an elevated risk of GDM and associated complications such as preeclampsia, gestational hypertension, fetal macrosomia, and higher rates of caesarean delivery ( 7 ). Additionally, maternal obesity has been linked to an increased likelihood of miscarriage, congenital anomalies due to hyperglycaemia during early organogenesis, and a heightened risk of venous thromboembolism ( 8 , 9 ). Given these adverse outcomes, clinical guidelines from the American College of Obstetricians and Gynecologists and the Institute of Medicine (IOM) recommend BMI assessments at the first antenatal visit, with specific gestational weight gain targets of 5–9 kg for women with obesity ( 7 , 10 ) Bariatric surgery (BS) is the most effective long-term intervention for obesity, with over half of procedures performed on women of reproductive age ( 11 , 12 ). A range of bariatric procedures are commonly performed including gastric banding, laparoscopic sleeve gastrectomy (LSG) and Roux-en-Y gastric bypass (RYGB). Mechanisms of weight loss are multifactorial and are not simply due to reduced food intake but rather a reset of the gastro-hormonal milieu, which ultimately increases satiety hormones, reduces hunger hormones and improves insulin sensitivity, a detailed discussion of which is beyond the scope of this paper ( 13 ). Post-operative weight loss and the associated metabolic adaptations have been associated with significant improvements in fertility and reduction in co-morbidities, including diabetes, hypertensive disorders, Asthma, etc. 11,14,15). However, women should be thoroughly counselled on the risks of early conception during this rapid weight loss phase, as malnutrition following BS can lead to insufficient gestational weight gain (GWG), small-for-gestational-age (SGA) neonates, and preterm birth ( 16 , 17 ). Maternal deficiencies in essential micronutrients such as folate, iron, vitamin B12 and fat-soluble vitamins have been linked to adverse perinatal outcomes, including neural tube defects, low birth weight, and preterm delivery ( 18 ). Conversely, some women may have insufficient weight loss (IWL) with impaired efficacy of the BS intervention, particulalry if pregnancy occurs before weight stabilization. While data suggest that fertility outcomes improve and the overall maternal and neonatal risks remain acceptable following BS, maintaining adequate maternal nutrition and vitamin supplementation remains critical to optimising pregnancy outcomes ( 19 – 21 ). Current consensus is to advise women to delay conception until achieving a stable weight following BS, typically beyond a minimum of 12 months, to reduce the risks of adverse pregnancy outcomes and above-mentioned nutritional deficiencies ( 22 – 25 ). However, in cases of advanced maternal age or diminished ovarian reserve, earlier conception may be considered, balancing potential benefits against residual obesity-related risks ( 22 ). A dichotomous cut-off of 12 months does not adequately reflect the complexity of post-surgical changes and a more nuanced approach to individual variation is key. Objectives: This systematic review and meta-analysis aims to provide an up-to-date evaluation of the impacts of BS on pregnancy outcomes while also examining the evidence regarding pregnancy timing after surgery. Understanding these variables is essential for optimising maternal and neonatal health, guiding clinical recommendations, and informing future research on long-term outcomes. MATERIALS AND METHODS This systematic review was conducted according to a registered protocol and is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The review was registered on PROSPERO Centre for Reviews and Dissemination (registration number: CRD42025622448). Literature search A comprehensive search was performed in electronic databases including Pubmed/Medline, EMBASE/OVID and the Cochrane library and they were reviewed from 2014 up to November 2024. The literature search included the following MeSH terms used in all possible combinations: “sleeve gastrectomy”, “gastric sleeve”, “LSG”, “laparoscopic sleeve gastrectomy”, “bariatric sleeve surgery”, “roux-en-y gastric bypass”, “gastric bypass”, “RYGB”, “revisional surgery”, “conversion surgery”, “repeat surgery”, “sleeve to bypass”, “sleeve gastrectomy to gastric bypass”. Studies identified from the search strategy were entered into Covidence (Victoria, Australia) for bibliographic management and duplicates were removed. Two authors, KW and MF independently identified relevant studies, and any discrepancies were resolved by a third reviewed (SB). The exact search strategy has been provided as supplementary material (Sup. 1). Eligibility criteria The inclusion and exclusion criteria were defined before the commencement of the literature search. The included studies provided clinical data and outcome rates on women of childbearing age who had undergone bariatric surgery for weight loss with subsequent pregnancy. Bariatric surgery referred to Laparoscopic sleeve gastrectomy (LSG), Roux-en-y gastric bypass (RYGB) or One-anastamosis gastric bypass (OAGB). Eligible study designs included randomised controlled trials (RCT), prospective or retrospective cohort studies, case (control) studies, cross-sectional studies and reviews. Both single-arm and double-arm comparative studies were included. Non-human studies, abstracts, conference presentations, single case reports, editorials and unpublished studies were excluded from the analysis. Quality assessment The quality of studies was assessed using the revised Cochrane's risk of bias tool (RoB2) for RCTs and the Newcastle-Ottawa scale for observational studies without randomisation ( 26 , 27 ) Data extraction and handling A standardised data extraction form was developed on Covidence and the authors AR, CN and JHY independently extracted all relevant data from full text study documents including: study design, sample size, type of bariatric surgery, mean/median maternal BMI (Body mass index), mean incidence of GDM; gestational hypertension, Pre-eclampsia, Pre-term labour, post-partum haemorrhage, anaemia and internal hernia (including SD). Mean APGAR scores, birthweight, gestational age, Neonatal ICU admission rates, Macrosomia, Intra-uterine growth restriction and peri-natal deaths were extracted. Any discrepancy was resolved by an independent reviewer (MF). Statistical Analysis Statistical analysis was performed using Stata Software (StataCorp LCC, TX, Version 15.1.) and RevMan (RevMan, Copenhagen: The Nordic Cochrane Centre, the Cochrane Collaboration, 2008). Random effects analysis was used to calculate pooled prevalence estimates for all studies across all outcomes. All studies were included in the meta-analysis if relevant data was available. When studies reported multiple bariatric subgroups, they were separated into distinct categories (e.g., A, B, C) and included as independent entries in the pooled analysis. For studies reporting data for both bariatric and control groups, study effect sizes were combined using odds ratios (OR) along with corresponding 95% confidence intervals (95% CI:) under the random-effects meta-analysis model (inverse variance method). For all results, the DerSimonian and Laird method was applied to account for between-study heterogeneity (I 2 ). We considered an I 2 of 30 or less as low, between 30 and 60 to be moderate, and 60 or over as high heterogeneity. Definition of outcomes The primary outcomes of interest were divided into maternal and neonatal. Maternal outcomes included: Gestational diabetes, gestational hypertension, pre-eclampsia, pre-term labour, C-section, induction of labour, postpartum haemorrhage, anaemia and internal hernia. Neonatal outcomes included: Apgar scores, birthweight, gestational age, NICU admission rates, macrosomia, intra-uterine growth restriction and perinatal death. Regarding timing of surgery: ‘Early’ refers to a bariatric surgery conception interval (BSCI) less than 12 months, and ‘Late’ refers to BSCI greater than 12 months. RESULTS Study Selection The search identified 2468 relevant citations. After removing duplicates, 1809 articles were screened for titles and abstracts, and 231 studies were included for full-text review. Following final screening, 129 studies met the inclusion criteria for quantitative synthesis (Fig. 1). Study Characteristics Of the 129 studies, 110 were retrospective (85.2%) and 19 were prospective (14.7%). Seventeen were multicentre studies and eight were national, with sample sizes ranging from 5 to 66,380 patients. The overall methodological quality of observational studies, assessed using the Newcastle–Ottawa Scale, was high (80.2%). Poor-quality studies were excluded (Suppl. 2). Among included participants, 45,970 patients (20.2%) had the bariatric procedure type specified, while 181,822 (79.8%) did not differentiate between LSG, RYGB, or OAGB. Patient Characteristics Mean maternal age ranged from 27.4 years to 38.1 years and the time of conception post bariatric surgery ranged from 1.4 to 92.4 months (IQR 20.3 to 39.9 months). Maternal Outcomes Time to conception Ninety-three studies reported the interval between surgery and conception, representing 10,644 patients. The pooled mean interval was 29 months (95% CI 27–32). The weighted mean time from RYGB to conception (1541 patients) was 29.5 months (95% CI 25.1–34.0), and from LSG (950 patients) was 24.3 months (95% CI 19.1–29.5). Pre-pregnancy weight loss Thirty-four studies, including 6845 patients, reported BMI before bariatric surgery and at conception. The pooled random-effects analysis demonstrated a mean BMI reduction of 14 kg/m² (95% CI 13–15) from pre-surgery to pre-pregnancy. Gestational weight gain Gestational weight gain (GWG) was reported in 76 studies involving 11,954 patients with prior bariatric surgery. The random-effects model estimated a pooled mean GWG of 9.66 kg (95% CI 8.53–10.79). Across 21 comparative studies, women with prior bariatric surgery gained less weight during pregnancy compared to obese controls (mean difference − 1.17 kg, 95% CI − 2.75 to − 0.40). In procedure-specific analyses, the random-effects weighted mean GWG was 9.33 kg (95% CI 7.79–10.86) after RYGB (17 studies) and 10.12 kg (95% CI 8.25–11.99) after LSG (17 studies). Gestational diabetes (GDM) The prevalence of GDM following bariatric surgery was 11% (95% CI 10–12) based on 82 studies including 177,926 patients. Across 39 comparative studies, bariatric surgery was associated with a significantly lower risk of GDM compared with obese controls (pooled OR 0.67, 95% CI 0.53–0.85). In 60 studies (21,755 patients) comparing conception intervals, the prevalence of GDM was 8% (95% CI 6–10) for BSCI 12 months. Comparative analysis across 13 studies found no significant difference between early and late conception groups (OR 0.83, 95% CI 0.57–1.20). Pre-eclampsia Fifty-four studies, including 171,635 patients, reported on pre-eclampsia, with a pooled prevalence of 5% (95% CI 4–8). In 27 comparative studies, the odds of pre-eclampsia were significantly lower among women with prior bariatric surgery than among obese controls (OR 0.60, 95% CI 0.45–0.79). Mode of delivery – Caesarean section and Induction of labour Ninety-five studies including 182,038 patients reported caesarean section rates after bariatric surgery, with a pooled prevalence of 38.6% (95% CI 36.9–40.3). Across 41 comparative studies, women with prior bariatric surgery had higher odds of caesarean delivery than obese controls (OR 1.24, 95% CI 1.01–1.52). Induction of labour was required in 28% of pregnancies after bariatric surgery (95% CI 22–34), based on 13 studies including 12,820 patients. In 12 comparative studies, women with prior bariatric surgery had higher odds of labour induction (OR 1.34, 95% CI 1.08–1.66). Postpartum haemorrhage Fifteen studies (18,615 patients) reported a pooled postpartum haemorrhage rate of 4% (95% CI 4–5). Sixteen comparative studies showed no significant difference between bariatric and control groups (pooled OR 1.17, 95% CI 0.64–2.23). Internal hernia Eleven studies including 4578 patients were included in the pooled analysis. The rate of internal herniation after RYGB was 2% (95% CI 1–4). Eight studies (3680 patients) reported diagnostic laparoscopy rates of 3% (95% CI 1–5). Anaemia and Vitamin deficiencies Nineteen studies including 4685 patients found a 26% prevalence (95% CI 22–31) of clinically relevant anaemia after bariatric surgery. Thirty-four studies (872 patients) reported micronutrient deficiencies as follows: zinc 19% (95% CI 11–27), vitamin A 61% (95% CI 54–68), vitamin B12 30% (95% CI 21–39), iron 33% (95% CI 27–39), calcium 16% (95% CI 8–23), and vitamin D 69% (95% CI 62–76). Vitamin A and D deficiencies were the most prevalent, whereas calcium and zinc deficiencies showed wider variation due to smaller sample sizes. Neonatal outcomes Birthweight Ninety studies, encompassing 14,204 neonates, reported birthweight. The weighted mean birthweight was 3092 g (95% CI 3056–3129) after RYGB (3107 neonates) and 3038 g (95% CI 3009–3068) after LSG (950 neonates). In 29 comparative studies, neonates born to women with prior bariatric surgery had a significantly lower mean birthweight than controls (mean difference − 205 g, 95% CI − 225 to − 186). Gestational age Thirty-two studies reported mean gestational age after RYGB, which included 2746 newborns as 270 days (95% CI: 268–271). Eleven studies, including 1095 neonates reported mean gestational age after LSG as 269 days (95% CI: 267–271). There was insufficient data available to perform a stratified analysis of GA for neonates born to mothers with a BSCI 12 months. Intra-uterine growth restriction A total of 27 studies involving 72,343 patients reported on intra-uterine growth restriction following bariatric surgery. The pooled effect size was 0.06 (95% CI: 0.05 to 0.07), indicating a low prevalence of 6% for this outcome within the post-surgical population. In the comparative analysis of 13 studies, women with prior bariatric surgery had significantly higher odds of intra-uterine growth restriction compared to controls (OR 2.09, 95% CI: 1.92 to 2.27). Macrosomia A total of 31 studies comprising 17,979 patients reported on macrosomia following bariatric surgery. The pooled effect size was 0.05 (95% CI: 0.04 to 0.07), indicating a low occurrence of macrosomia in this population. However, substantial heterogeneity was observed (I² = 87.7%). In a pooled analysis of 19 studies, women with a history of bariatric surgery had significantly lower odds of delivering a macrosomic neonate compared to controls (OR 0.35, 95% CI: 0.24 to 0.50). Heterogeneity was considerable (I² = 87%). There was insufficient data to perform a stratified analysis according to timing of pregnancy after surgery. Pre-term Birth A total of 125 studies, including 121,994 patients, reported on preterm birth among women with prior bariatric surgery. The pooled effect size was 0.10 (95% CI: 0.03–0.11), corresponding to a prevalence of 10%. Heterogeneity was high (I² = 85.2%). In the comparative analysis of 33 studies, women with a history of bariatric surgery had higher odds of preterm birth compared to controls (OR 1.24, 95% CI: 1.04–1.47). Heterogeneity across studies was considerable (I² = 95%), indicating substantial variability in the reported effect estimates. Low APGAR scores (< 7) at 5 minutes Among 10,847 neonates born to mothers with bariatric surgery, the prevalence of low 5-minute APGAR scores was 1.7% (95% CI 1.2–2.2). Thirteen comparative studies showed higher odds of a low APGAR score in the bariatric group (OR 1.38, 95% CI 1.07–1.79). Admission to Neonatal Intensive Care Unit (NICU) Seventy-four studies (11,936 neonates) reported a NICU admission rate of 12% (95% CI 10–14). In 24 comparative studies, neonates of mothers with prior bariatric surgery had higher odds of NICU admission than those of controls (OR 1.39, 95% CI 1.17–1.65). There was insufficient data to perform a stratified analysis according to timing of pregnancy after surgery. Perinatal deaths Twelve studies including 66,553 patients reported a pooled perinatal mortality rate of 2% (95% CI 1–2). Comparative analysis indicated no statistically significant difference in perinatal mortality between groups (OR 1.36, 95% CI 1.00–1.85). Other complications Analysis of other significant complications (defined as Clavien-Dindo severity greater than or equal to 3) was pooled from 15 studies including 14727 patients ( 28 ). Complications with a severity of Clavien-Dindo 3 or higher i.e. those requiring surgical, endoscopic or radiological intervention, intensive care admission or mortality were reported in 5% (95%CI: 4%-7%). Table 1. to be placed here Subgroup Analysis – Early ( 12 months) pregnancy post-op Gestational Weight Gain In the early conception group (BSCI 12 months; 3859 patients), it was 10.2 kg (95% CI 9.47–11.11). Across 15 studies, late conception was associated with significantly greater GWG (mean difference 5.07 kg, 95% CI 2.53–7.60). Pre-term Birth In pooled subgroup analysis, the risk of preterm birth was 12% (95% CI 7–16) in the early pregnancy group and 11% (95% CI 9–13) in the late group. Comparative analysis of 13 studies found no significant difference between groups (OR 0.88, 95% CI 0.61–1.27). Figure 1. to be placed here DISCUSSION Main findings: This systematic review and meta-analysis revealed reduced odds of developing GDM, pre-eclampsia and fetal macrosomia in pregnancies after BS compared to women with obesity. Conversely, BS was found to be associated with greater odds of undergoing C-section delivery or induction of labour with no significant impact on the odds of post-partum haemorrhage. Conversely, neonates born to women who have undergone BS have higher odds of IUGR, admission to NICU care and Apgars < 7 at 5 minutes but with no significant difference in peri-natal mortality. Maternal Outcomes Our findings confirm that BS is an effective intervention for pre-pregnancy weight loss and significantly reduces average pre-pregnancy BMI. This supports published meta-analyses, which found the reduction in pre-pregnancy BMI (averaging 13.93kg/m2) does not significantly change during early pregnancy and pre-delivery, indicating that weight management is likely to remain stable during pregnancy after initial post-surgery weight loss ( 40 ). Gestational weight gain Gestational weight gain (GWG) remains a complex issue and is critical for a number of important clinical outcomes, including fetal growth and wellbeing, delivery method, and the risk of weight regain or recurrence of obesity-related co-morbidities. The existing literature links excessive GWG with increased risk of macrosomia, large-for-gestational-age (LGA) infants, caesarean delivery, and GDM, while insufficient GWG correlates with higher risks of IUGR, small-for-gestational-age (SGA) infants, preterm birth, and NICU admissions ( 16 – 18 , 22 – 25 ). Our meta-analysis supports these associations. The prevalence of IUGR was 3% higher in women post-BS compared to women with obesity, whereas macrosomia was 7% less frequent, indicating a trade-off in fetal growth outcomes that requires tailored antenatal monitoring. The Institute of Medicine (IOM) provides guidelines based on pre-pregnancy BMI, recommending weight gain of 11.5–16 kg for women with a normal BMI (18.5–24.9), 6.8–11.3 kg for those who are overweight (BMI 25–29.9), and 5–9.1 kg for women with obesity (BMI ≥ 30) ( 29 ). Our findings suggest women who have undergone BS and reduced pre-pregnancy BMI to < 30kg/m² tend to achieve these targets. Critics of the current IOM guidelines have argued that the weight gain targets are too high, particularly as they do not address concerns regarding post-partum weight retention. Additionally, they do not differentiate between degrees of obesity (Class I to III), which is relevant in the post-bariatric cohort, given that our study found women post-BS have reduced their pre-pregnancy BMI by an average of 14 kg/m² but may still fall within the broad class of obesity (BMI > 30) ( 28 ). Furthermore, subgroup analysis demonstrated significantly greater GWG in the late conception group compared to the early conception group (mean difference 5.07 kg), but without significant differences in the odds of GDM or prematurity between subgroups. This finding highlights that maternal weight gain is not the only factor contributing to these observed associations. For patients and clinicians, comparing GWG between procedures, our meta-analysis found that women who had undergone RYGB gained slightly less weight during pregnancy (9.33kg) compared to LSG (10.12kg), however with overlapping confidence intervals and high heterogeneity, this difference may not be clinically significant. Previous individual studies reported no difference in GWG between RYGB and SG ( 3 ) Overall, our findings underscore that sufficient GWG is necessary for fetal growth, but both inadequate and excessive gain can complicate outcomes in post-bariatric patients. Further IOM guidelines specific for post-bariatric surgery mothers would be useful for clinicians treating this expanding cohort of women. Gestational Diabetes and Pre-eclampsia Our findings support the established literature that BS is associated with significant reduction in major obesity-related pregnancy complications, most notably GDM and pre-eclampsia, compared to obese women without prior BS ( 15 , 16 ). The prevalence of GDM after BS was 11% based on our findings from the largest known pooled sample in the literature. To contextualize this, the reported pooled global standardized prevalence of GDM is 14% across all pregnancies ( 6 ). Thus, BS reduces GDM risk to below the baseline population level. Furthermore, previous meta-analyses demonstrated that the risk of GDM increases with increased BMI in a dose-dependent pattern ( 31 ). Thus, our findings support the existing evidence by demonstrating that BS dramatically decreases pre-pregnancy BMI with an expected reduction in the odds of GDM. While the pathophysiology of pre-eclampsia is thought to be linked with abnormal placentation, obesity and excessive weight gain are established risk factors. We found the odds of pre-eclampsia were 40% lower in the bariatric group than in controls. Previous literature has demonstrated similar findings ( 15 ). These likely reflect the metabolic improvements attributed to the BRAVE effects described in the literature with the following components: bile flow alteration, reduction in gastric size, anatomical gut rearrangement and altered flow of nutrients, vagal manipulation, and enteric gut modulation ( 12 , 22 ). Established literature supports remission of diabetes after BS, with RYGB superior in this outcome compared to LSG ( 12 ) and our findings underscore the preventative benefits of RYGB in reducing odds of GDM in pregnancy, through similar metabolic alterations described above. Screening for GDM in post-bariatric surgery is nevertheless important, and a particular consideration is that standardized oral glucose tolerance testing (OGTT) is often poorly tolerated by women who have undergone procedures like RYGB, LSG and Biliary-pancreatic diversion as these can trigger dumping syndrome ( 30 ). Thus, alternative strategies such as multi-point home glucose monitoring and HbA1C may need to be considered ( 22 , 30 ). Delivery methods The mode of delivery was significantly affected by a history of BS, with higher odds of requiring caesarean section and induction of labour in women post-bariatric surgery when compared to obese controls. While this may seem paradoxical it may reflect underlying obstetric risk factors, altered anatomy, or clinical decision-making biases, and the findings warrant further exploration to optimise delivery planning and counselling. Further studies stratifying the urgency of delivery and indications for C-section or labour induction would be beneficial to explore this association. Furthermore, instrumental delivery methods could be included in analysis in future reviews as previous literature has found BS reduces these odds significantly. There was insufficient data to analyze whether delivery methods were impacted by time interval from BS, and further studies would be helpful for both patients and clinicians. Post surgical complications Our meta-analysis found that rates of internal hernia after RYGB were low at 2%. And likewise, the rate of diagnostic laparoscopy during pregnancy was 3%. Previous evidence has reported that RYGB presents the greatest risk of surgical complications during pregnancy, with internal herniation occurring in 8% of post-surgical pregnancies and the most common location of the hernia was Petersen's space ( 22 ). This is a feared complication and previous reviews found that all maternal and perinatal deaths in pregnancies complicated by internal herniation after RYGB occurred in women treated later than 48 hours after symptom onset. Therefore, despite our findings of a lower incidence than previously reported, a high index of suspicion is required. The presentation may be non-specific, including abdominal pain and vomiting, thus all women of reproductive age undergoing RYGB should be thoroughly counselled on the lifelong risk of this complication to avoid delayed diagnosis and treatment ( 30 ). Should clinicians suspect the diagnosis of internal herniation, a multi-disciplinary approach is required when considering the risks versus benefits of diagnostic laparoscopy, CT imaging and even newer modalities such as 3D modelling to confirm diagnosis ( 32 ). Ultimately, delays in diagnosis will impact maternal and fetal outcomes, therefore balancing surgical risks, radiation exposure and anaesthetic risks all need careful consideration. Another consideration, particularly in pregnancies after LSG is the greater risk of gastro-oesophageal reflux disease (GORD), which already occurs in up to two-thirds of pregnancies ( 33 ). While the condition itself is benign, it can significantly affect quality of life and can predispose to Barrett’s oesophagus as a pre-malignant condition. In obese women, the effect of pregnancy hormones can exacerbate or cause de novo GORD, particularly in post-surgical mothers who have undergone LSG compared to RYGB ( 12 , 34 ). Our review of the literature found that papers rarely assessed this maternal outcome, and further studies are needed to analyze the effects of timing of pregnancy after surgery and the differences according to surgery type on GORD incidence, severity and sequelae. While antacids, proton-pump inhibitors and Sucralfate are amongst the medical treatment options, refractory cases may require surgical approaches such as fundoplication, or magnetic sphincter augmentation, but further research is needed regarding the implications of these in pregnancy ( 33 , 35 ). Maternal nutrition Our meta-analysis found the overall risk of clinically relevant anaemia to be 26% after all bariatric surgery. Specifically, the prevalence of iron-deficiency in post-surgical patients was 33%, albeit with notable variation between cohorts. The reported global prevalence of anaemia in pregnant women is 36.8%, thus our findings are in keeping with global averages ( 36 ). However, it is important to understand the pathophysiology of iron-deficiency anaemia (IDA) in BS, as these patients will have reduced production of hydrochloric acid in the stomach, which is necessary to convert dietary iron in the ferric form into the ferrous state. Furthermore, the reduced intake of meat and the reduction of intestinal iron absorption capacity due to bypassing are other contributors to the observed IDA ( 19 ). This can further exacerbate the physiological anaemia observed in pregnancy and certainly requires careful monitoring. Both Vitamin A and D deficiency were demonstrated with a high prevalence of 61% and 69% respectively. This is in keeping with established literature reporting that fat-soluble vitamin deficiencies (A, D, E, K) are common after bariatric surgery due to bypassing absorption sites, reduced bile mixing, and fat malabsorption ( 37 ). Vitamin D and A are most affected, with established associations in existing literature to bone, vision, and immune issues ( 38 ). Morgan et al. (2025) recently published guidance advising supplementation and blood-test monitoring of these nutrients in each trimester ( 30 ). This is essential given the high prevalences found in our study. Specifically regarding vitamin A, these pregnant women should avoid retinol/retinyl esters forms and instead take vitamin A exclusively in the beta‑carotene form under medical supervision to prevent the risks of congenital anomalies ( 16 , 39 ). Neonatal Outcomes Fetal Growth Several important trends emerged in neonatal outcomes. As discussed above, infants born to mothers with prior BS had greater odds of IUGR and preterm birth. These findings support the hypothesis that rapid maternal weight loss and nutritional deficits may adversely affect fetal growth. Conversely, our study found that BS significantly reduced the odds of macrosomia, which is an expected benefit in this population based on existing literature. Overall, we found neonates born to women after BS weighed over 200g less than neonates born to obese mothers. This finding is consistent with previous meta-analyses in the literature ( 31 , 40 ). These findings underscore the importance of antenatal nutritional monitoring, targeted supplementation and adherence to GWG targets, particularly in mothers who are within 12 months of BS who may be at greater risk for anemia and fat-soluble vitamin deficiencies described above. APGAR scores, NICU admissions and peri-natal mortality NICU admission rates (12%) and low Apgar scores < 7 at 5 min (1.7%) were both slightly elevated in the bariatric surgery cohort. While these rates were modest, they reflect a need for heightened neonatal surveillance and underscore the importance of coordinated perinatal care. These variables may also reflect the confounding effects of both IUGR and prematurity on the risk of NICU admission. Adopting a nuanced approach in this obstetric population may be prudent because although the odds of preterm birth did not significantly differ between early and late groups, there remains insufficient data on whether timing of pregnancy after BS correlates with IUGR, admission to NICU or perinatal mortality. More studies are needed to clarify the impact of BS on these critical clinical outcomes, perhaps modeling the time-interval from surgery to pregnancy as a continuous variable rather than a dichotomous cut-off. Importantly, perinatal mortality rates were low (0.2%) and not significantly different between neonates born to women post-bariatric surgery compared to obese mothers, providing reassurance regarding overall fetal viability. A previous meta-analysis by Akhter et al. (2019) found the odds of peri-natal mortality to be increased after BS ( 39 ). However, our results border on statistical significance and may nevertheless justify heightened clinical vigilance. Timing of Conception Post-Surgery Subgroup analyses based on time interval to conception (12 months post-bariatric surgery) provided valuable clinical insights; however, their interpretation is constrained by heterogeneity across studies and limited sample sizes. Early conception within 12 months was associated with lower GWG, a non-significant increased odd of preterm birth, and no appreciable difference in the odds of GDM compared to later conception. These findings lend cautious support to current clinical guidelines recommending a minimum 12-month interval before conception to promote metabolic stabilisation and mitigate nutritional risks, which may be higher if the rapid weight loss phase post-surgery overlaps with early pregnancy. Nonetheless, future research should consider modeling time to conception as a continuous variable to better capture its relationship with maternal and neonatal outcomes, and to offer more nuanced guidance for clinical decision-making. Study Quality and Limitations The strength of this study includes the large pool of articles included in the original search. However, high heterogeneity in several analyses result from variability in study design, population characteristics, and surgical techniques, affecting generalizability. The limitations include the lack of RCTs and prospective data collection, smaller case-series, large heterogeneity in some analysis, unmeasured confounders and limited studies comparing early versus late conception at consistent intervals. Lack of detailed data on nutritional status and micronutrient deficiencies stratified according to pregnancy timing and surgery type limits recommendations for post-bariatric surgery pregnancies. Reduced opportunity to conduct randomized controlled trials in this population limits evidence strength, relying on observational studies. Most included studies were retrospective in nature (85.2%), introducing potential for selection, recall and reporting bias, confounding variables, and missing data. Although study quality was generally high per the Newcastle-Ottawa Scale, heterogeneity across outcomes was considerable (I² > 80% in many analyses), reflecting variation in patient characteristics, surgical procedures, definitions of outcomes, and follow-up protocols. Importantly, many studies did not differentiate between specific types of bariatric procedures (e.g., LSG vs. RYGB), limiting the ability to draw procedure-specific conclusions. Given the distinct anatomical and absorptive alterations associated with different surgeries, future research should stratify by surgery type to enable more nuanced guidance. Conclusion This systematic review and meta-analysis demonstrates that BS prior to pregnancy significantly reduces the risk of obesity-related complications such as gestational diabetes, pre-eclampsia, and fetal macrosomia. However, BS is also associated with increased odds of caesarean delivery, labour induction, intrauterine growth restriction, NICU admission, and low Apgar scores, highlighting a complex balance of maternal and neonatal risks. The substantial heterogeneity across studies reflects variations in surgical procedures, patient characteristics, and timing of conception, highlighting the importance of individualised care, multidisciplinary antenatal management, and robust preconception counselling. Nutritional deficiencies, particularly in iron and fat-soluble vitamins, were frequent and warrant vigilant monitoring and supplementation throughout pregnancy. These findings support current guidelines recommending delayed conception for at least 12 months post-surgery to allow for nutritional stabilisation but emphasise the need for gestational weight gain guidelines tailored to this population. Critically, this review identifies key evidence gaps, including the need for high-quality prospective studies and refined analyses that model time from surgery to pregnancy as a continuous variable to account for the nuances of individual variation in weight stabilisation and better risk stratification. Addressing these gaps will advance clinical practice and support safer, more tailored care for women navigating pregnancy after bariatric surgery. Declarations Contributor and guarantor information The study was conceived by MF and designed by MF, WL MK, YAA. The data was acquired and collated by MF, AR, CN, JHY, KW, SB and analysed by KW, SB, MF. The manuscript was drafted and revised critically for important intellectual content by all authors. All authors gave final approval of the version to be published. The corresponding author (MF) attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. The guarantor (MF) accepts full responsibility for the work, had access to the data, and controlled the decision to publish. Funding No external funding was received for this study Competing interest declaration The authors declare no conflict of interest with regards to the presented work. Ethics approval and patient consent Ethical approval was not required for this systematic review and meta-analysis. Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information Transparency declaration The lead author (KW) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained. All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organisations. Patient Involvement and Dissemination The research questions and outcomes were formulated based on patients' concerns and priorities. While patients were not directly involved in interpreting results or writing the article, efforts will be made to share findings with the lay audience through various channels, including press releases, social media, and authors' engagements with charities, public presentations and interviews. References Yu Y, Ma Q, Groth SW. Risk factors for preterm birth in pregnancies following bariatric surgery: an analysis of the Longitudinal Assessment of Bariatric Surgery-2. Surg Obes Relat Dis. 2022;18(11):1304–12. Slack E, Best KE, Rankin J, Heslehurst N. Maternal obesity classes, preterm and post-term birth: a retrospective analysis of 479,864 births in England. BMC Pregnancy Childbirth. 2019;19(1):434. Sheiner E, Balaban E, Dreiher J, Levi I, Levy A. Pregnancy Outcome in Patients Following Different Types of Bariatric Surgeries. Obes Surg. 2009;19(9):1286–92. Sheiner E, Edri A, Balaban E, Levi I, Aricha-Tamir B. Pregnancy outcome of patients who conceive during or after the first year following bariatric surgery. Am J Obstet Gynecol. 2011;204(1):50.e1-50.e6. Wang YH, Wu HH, Ding H, Li Y, Wang ZH, Li F, et al. Changes of insulin resistance and β-cell function in women with gestational diabetes mellitus and normal pregnant women during mid- and late pregnant period: a case-control study. J Obstet Gynaecol Res. 2013;39(3):647–52. Wang H, Li N, Chivese T, Werfalli M, Sun H, Yuen L, et al. IDF Diabetes Atlas: Estimation of Global and Regional Gestational Diabetes Mellitus Prevalence for 2021 by International Association of Diabetes in Pregnancy Study Group’s Criteria. Diabetes Res Clin Pract. 2022;183:109050. Marchi J, Berg M, Dencker A, Olander EK, Begley C. Risks associated with obesity in pregnancy, for the mother and baby: a systematic review of reviews. Obes Rev. 2015;16(8):621–38. Poston L, Caleyachetty R, Cnattingius S, Corvalán C, Uauy R, Herring S, et al. Preconceptional and maternal obesity: epidemiology and health consequences. Lancet Diabetes Endocrinol. 2016;4(12):1025–36. Kourlaba G, Relakis J, Kontodimas S, Holm MV, Maniadakis N. A systematic review and meta-analysis of the epidemiology and burden of venous thromboembolism among pregnant women. Int J Gynecol Obstet. 2016;132(1):4–10. Martínez-Hortelano JA, Cavero-Redondo I, Álvarez-Bueno C, Garrido-Miguel M, Soriano-Cano A, Martínez-Vizcaíno V. Monitoring gestational weight gain and prepregnancy BMI using the 2009 IOM guidelines in the global population: a systematic review and meta-analysis. BMC Pregnancy Childbirth. 2020;20(1):649. Edison E, Whyte M, van Jones VJ, de Gatenby S. Bariatric Surgery in Obese Women of Reproductive Age Improves Conditions That Underlie Fertility and Pregnancy Outcomes: Retrospective Cohort Study of UK National Bariatric Surgery Registry (NBSR). Obes Surg. 2016;26(12):2837–42. Fehervari M, Banh S, Varma P, Das B, Al-Yaqout K, Al-Sabah S, et al. Weight loss specific to indication, remission of diabetes, and short-term complications after sleeve gastrectomy conversion to Roux-en-Y gastric bypass: a systematic review and meta-analysis. Surg Obes Relat Dis. 2023;19(4):384–9. Meek CL, Lewis HB, Reimann F, Gribble FM, Park AJ. The effect of bariatric surgery on gastrointestinal and pancreatic peptide hormones. Peptides. 2016;77:28–37. Maggard MA, Yermilov I, Li Z, Maglione M, Newberry S, Suttorp M, et al. Pregnancy and fertility following bariatric surgery: a systematic review. JAMA. 2008;300(19):2286–96. Galazis N, Docheva N, Simillis C, Nicolaides KH. Maternal and neonatal outcomes in women undergoing bariatric surgery: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2014;181:45–53. Johansson K, Cnattingius S, Näslund I, Roos N, Trolle Lagerros Y, Granath F, et al. Outcomes of Pregnancy after Bariatric Surgery. N Engl J Med. 2015;372(9):814–24. Grandfils S, Demondion D, Kyheng M, Duhamel A, Lorio E, Pattou F, et al. Impact of gestational weight gain on perinatal outcomes after a bariatric surgery. J Gynecol Obstet Hum Reprod. 2019;48(6):401–5. Stephansson O, Johansson K, Söderling J, Näslund I, Neovius M. Delivery outcomes in term births after bariatric surgery: Population-based matched cohort study. Myers JE, editor. PLOS Med. 2018;15(9):e1002656. Devlieger R, Guelinckx I, Jans G, Voets W, Vanholsbeke C, Vansant G. Micronutrient Levels and Supplement Intake in Pregnancy after Bariatric Surgery: A Prospective Cohort Study. PLoS ONE. 2014;9(12):e114192. Maslin K, James A, Brown A, Bogaerts A, Shawe J. What Is Known About the Nutritional Intake of Women during Pregnancy Following Bariatric Surgery? A Scoping Review. Nutrients. 2019;11(9):2116. Jans G, Guelinckx I, Voets W, Galjaard S, Van Haard PMM, Vansant GM, et al. Vitamin K1 monitoring in pregnancies after bariatric surgery: a prospective cohort study. Surg Obes Relat Dis. 2014;10(5):885–90. Shawe J, Ceulemans D, Akhter Z, Neff K, Hart K, Heslehurst N, et al. Pregnancy after bariatric surgery: Consensus recommendations for periconception, antenatal and postnatal care. Obes Rev Off J Int Assoc Study Obes. 2019;20(11):1507–22. Ciangura C, Coupaye M, Deruelle P, Gascoin G, Calabrese D, Cosson E, et al. Clinical Practice Guidelines for Childbearing Female Candidates for Bariatric Surgery, Pregnancy, and Post-partum Management After Bariatric Surgery. Obes Surg. 2019;29(11):3722–34. Heusschen L, Krabbendam I, Van Der Velde JM, Deden LN, Aarts EO, Merién AER, et al. A Matter of Timing—Pregnancy After Bariatric Surgery. Obes Surg. 2021;31(5):2072–9. Carreira A, Araújo B, Lavrador M, Vieira I, Rodrigues D, Paiva S, et al. From Bariatric Surgery to Conception: The Ideal Timing to Optimize Fetal Weight. Obes Surg. 2023;33(9):2859–65. Sterne JAC, Savović J, Page MJ, Elbers RG, Blencowe NS, Boutron I et al. RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ. 2019;l4898. Wells G, Wells G, Shea B, Shea B, O’Connell D, Peterson J et al. The Newcastle-Ottawa Scale (NOS) for Assessing the Quality of Nonrandomised Studies in Meta-Analyses. In 2014 [cited 2025 Jan 22]. Available from: https://www.semanticscholar.org/paper/The-Newcastle-Ottawa-Scale-(NOS)-for-Assessing-the-Wells-Wells/c293fb316b6176154c3fdbb8340a107d9c8c82bf Dindo D, Demartines N, Clavien PA. Classification of Surgical Complications. Ann Surg. 2004;240(2):205–13. Ceulemans D, De Mulder P, Lebbe B, Coppens M, De Becker B, Dillemans B, et al. Gestational weight gain and postpartum weight retention after bariatric surgery: data from a prospective cohort study. Surg Obes Relat Dis. 2021;17(4):659–66. Morgan HD, Morrison AE, Hamza M, Jones C, Cassar CB, Meek CL. The approach to a pregnancy after bariatric surgery. Clin Med. 2024;25(1):100275. Chu SY, Callaghan WM, Kim SY, Schmid CH, Lau J, England LJ, et al. Maternal obesity and risk of gestational diabetes mellitus. Diabetes Care. 2007;30(8):2070–6. Robb HD, Arif A, Narendranath RM, Das B, Alyaqout K, Lynn W, et al. How is 3D modeling in metabolic surgery utilized and what is its clinical benefit: a systematic review and meta-analysis. Int J Surg Lond Engl. 2025;111(5):3159–68. Altuwaijri M. Evidence-based treatment recommendations for gastroesophageal reflux disease during pregnancy: A review. Med (Baltim). 2022;101(35):e30487. Sargsyan N, Ali I, Namgoong C, Das B, Fehervari M, Fadel MG. Gastro-Oesophageal Reflux Disease Outcomes Following Roux-en-Y Gastric Bypass Surgery in Patients with Obesity: A Systematic Review and Meta-analysis. Obes Surg. 2025;35(6):2321–32. Fadel MG, Tarazi M, Dave M, Reddy M, Khan O, Fakih-Gomez N, et al. Magnetic sphincter augmentation in the management of gastro-esophageal reflux disease: a systematic review and meta-analysis. Int J Surg Lond Engl. 2024;110(10):6355–66. Karami M, Chaleshgar M, Salari N, Akbari H, Mohammadi M. Global Prevalence of Anemia in Pregnant Women: A Comprehensive Systematic Review and Meta-Analysis. Matern Child Health J. 2022;26(7):1473–87. Mechanick JI, Youdim A, Jones DB, Garvey WT, Hurley DL, McMahon M, et al. Clinical Practice Guidelines for the Perioperative Nutritional, Metabolic, and Nonsurgical Support of the Bariatric Surgery Patient—2013 Update: Cosponsored by American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic & Bariatric Surgery. Obes Silver Spring Md. 2013;21(0 1):S1–27. Heber D, Greenway FL, Kaplan LM, Livingston E, Salvador J, Still C, et al. Endocrine and nutritional management of the post-bariatric surgery patient: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2010;95(11):4823–43. Akhter Z, Rankin J, Ceulemans D, Ngongalah L, Ackroyd R, Devlieger R, et al. Pregnancy after bariatric surgery and adverse perinatal outcomes: A systematic review and meta-analysis. PLoS Med. 2019;16(8):e1002866. Arbis A, Rafay A, Namgoong C, Yoon JH, Ashrafian H, Fehervari M et al. The impact of bariatric surgery on maternal and neonatal health: a systematic review and meta-analysis. Surg Obes Relat Dis Off J Am Soc Bariatr Surg. 2025;S1550-7289(25)00112-1. Table 1 Table 1. Summary of maternal and neonatal outcomes following bariatric Surgery: pooled proportions and comparative meta-analysesh Pooled Outcome Rates in Women with a History of Bariatric Surgery Outcome No. of Studies (n) Effect Estimate (95% CI) Gestational weight gain (kg) 106 9.66 [8.53, 10.79] Gestational diabetes (GDM) 82 0.11 [0.10, 0.12] Pre-eclampsia 54 0.05 [0.04, 0.08] Caesarean section 95 0.39 [0.37, 0.40] Induction of labour 13 0.28 [0.22, 0.34] Postpartum haemorrhage 15 0.04 [0.04, 0.05] NICU admission 74 0.12 [0.10, 0.14] Preterm birth 78 0.101 [0.03, 0.11] Intrauterine growth restriction (IUGR) 27 0.06 [0.05, 0.07] Macrosomia 31 0.05 [0.04, 0.07] Low APGAR (<7 at 5 min) 33 0.02 [0.01, 0.02] Anaemia 19 0.26 [0.22, 0.31] Vitamin deficiencies 12 0.04 [0.03, 0.05] Internal hernia 11 0.02 [0.01, 0.04] Diagnostic laparoscopy (hernia) 8 0.03 [0.01, 0.05] Comparative Outcomes: Bariatric Surgery vs. Non-Surgical Controls Outcome No. of Studies (n) OR/Mean Difference (95% CI) Gestational weight gain 21 –1.17 kg [–2.75, 0.40] Gestational diabetes (GDM) 39 0.67 [0.53, 0.85]*** Pre-eclampsia 27 0.60 [0.45, 0.79]*** Caesarean section 41 1.24 [1.01, 1.52]* Induction of labour 12 1.34 [1.08, 1.66]** Postpartum haemorrhage 16 1.17 [0.64, 2.23] NICU admission 24 1.39 [1.17, 1.65]** Preterm birth 33 1.24 [1.04, 1.47]* Birthweight 29 –205.38 [–224.86, –185.90]*** IUGR 13 2.09 [1.92, 2.27]*** Macrosomia 19 0.35 [0.24, 0.50]*** Low APGAR (<7 at 5 min) 13 1.38 [1.07, 1.79]** Perinatal deaths - - Pooled estimates were derived using a DerSimonian–Laird random effects model. Proportions represent pooled single-arm event rates among women with a history of bariatric surgery. Comparative estimates (ORs or mean differences) reflect outcome differences between bariatric surgery and non-surgical control groups. Studies reporting multiple surgical subgroups were included separately in pooled estimates if data were stratified. *p-value<0.05, ** p-value<0.01, *** p-value<0.001. Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterial.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 13 Mar, 2026 Editor assigned by journal 13 Mar, 2026 Submission checks completed at journal 10 Mar, 2026 First submitted to journal 28 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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16:38:34","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8723438/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8723438/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104876289,"identity":"cbfd65c6-9f07-400b-a939-1edb048d789e","added_by":"auto","created_at":"2026-03-18 08:42:12","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":627976,"visible":true,"origin":"","legend":"\u003cp\u003eComparative subgroup analysis forest plots on early (\u0026lt;12 months) vs late (\u0026gt;12 months) pregnancy post-op: (a) Gestational diabetes (GDM), (b) Gestational weight gain (GWG), (c) Preterm birth.\u003c/p\u003e","description":"","filename":"Figures.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8723438/v1/6cc75fed7fcc2001cdec6de8.jpg"},{"id":104876585,"identity":"bd9ad085-d75d-4680-a36d-cf45c8c6da51","added_by":"auto","created_at":"2026-03-18 08:43:01","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1856716,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8723438/v1/ea713ed7-341b-4874-8601-1849d161ed92.pdf"},{"id":104876345,"identity":"6beb0514-51f7-4fbe-9c22-1e26e488e2b5","added_by":"auto","created_at":"2026-03-18 08:42:17","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":247939,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-8723438/v1/a8dc1addd21b0a3755be8325.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Impact of Bariatric Surgery on Pregnancy: A Systematic Review and Meta-analysis ","fulltext":[{"header":"Background","content":"\u003cp\u003eMaternal obesity, defined as a pre-pregnancy body mass index (BMI) of \u0026ge;\u0026thinsp;30 kg/m\u0026sup2;, presents significant risks for both mother and foetus (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Despite growing awareness, maternal obesity has reached epidemic proportions, with prevalence rates of 31.9% in the United States, 21.3% in the United Kingdom, and similar increasing trends across Europe (\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDuring pregnancy, physiological insulin resistance increases due to placental secretion of diabetogenic hormones, including growth hormone, corticotropin-releasing hormone, placental lactogen, and prolactin, predisposing women to gestational diabetes mellitus (GDM) (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Obese women experience a more pronounced decline in insulin sensitivity than those with normal weight, leading to an elevated risk of GDM and associated complications such as preeclampsia, gestational hypertension, fetal macrosomia, and higher rates of caesarean delivery (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Additionally, maternal obesity has been linked to an increased likelihood of miscarriage, congenital anomalies due to hyperglycaemia during early organogenesis, and a heightened risk of venous thromboembolism (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Given these adverse outcomes, clinical guidelines from the American College of Obstetricians and Gynecologists and the Institute of Medicine (IOM) recommend BMI assessments at the first antenatal visit, with specific gestational weight gain targets of 5\u0026ndash;9 kg for women with obesity (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eBariatric surgery (BS) is the most effective long-term intervention for obesity, with over half of procedures performed on women of reproductive age (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). A range of bariatric procedures are commonly performed including gastric banding, laparoscopic sleeve gastrectomy (LSG) and Roux-en-Y gastric bypass (RYGB). Mechanisms of weight loss are multifactorial and are not simply due to reduced food intake but rather a reset of the gastro-hormonal milieu, which ultimately increases satiety hormones, reduces hunger hormones and improves insulin sensitivity, a detailed discussion of which is beyond the scope of this paper (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Post-operative weight loss and the associated metabolic adaptations have been associated with significant improvements in fertility and reduction in co-morbidities, including diabetes, hypertensive disorders, Asthma, etc. 11,14,15). However, women should be thoroughly counselled on the risks of early conception during this rapid weight loss phase, as malnutrition following BS can lead to insufficient gestational weight gain (GWG), small-for-gestational-age (SGA) neonates, and preterm birth (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Maternal deficiencies in essential micronutrients such as folate, iron, vitamin B12 and fat-soluble vitamins have been linked to adverse perinatal outcomes, including neural tube defects, low birth weight, and preterm delivery (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). Conversely, some women may have insufficient weight loss (IWL) with impaired efficacy of the BS intervention, particulalry if pregnancy occurs before weight stabilization. While data suggest that fertility outcomes improve and the overall maternal and neonatal risks remain acceptable following BS, maintaining adequate maternal nutrition and vitamin supplementation remains critical to optimising pregnancy outcomes (\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCurrent consensus is to advise women to delay conception until achieving a stable weight following BS, typically beyond a minimum of 12 months, to reduce the risks of adverse pregnancy outcomes and above-mentioned nutritional deficiencies (\u003cspan additionalcitationids=\"CR23 CR24\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). However, in cases of advanced maternal age or diminished ovarian reserve, earlier conception may be considered, balancing potential benefits against residual obesity-related risks (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). A dichotomous cut-off of 12 months does not adequately reflect the complexity of post-surgical changes and a more nuanced approach to individual variation is key.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjectives:\u003c/strong\u003e This systematic review and meta-analysis aims to provide an up-to-date evaluation of the impacts of BS on pregnancy outcomes while also examining the evidence regarding pregnancy timing after surgery. Understanding these variables is essential for optimising maternal and neonatal health, guiding clinical recommendations, and informing future research on long-term outcomes.\u0026nbsp;\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cp\u003e This systematic review was conducted according to a registered protocol and is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The review was registered on PROSPERO Centre for Reviews and Dissemination (registration number: CRD42025622448).\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eLiterature search\u003c/h2\u003e \u003cp\u003eA comprehensive search was performed in electronic databases including Pubmed/Medline, EMBASE/OVID and the Cochrane library and they were reviewed from 2014 up to November 2024. The literature search included the following MeSH terms used in all possible combinations: \u0026ldquo;sleeve gastrectomy\u0026rdquo;, \u0026ldquo;gastric sleeve\u0026rdquo;, \u0026ldquo;LSG\u0026rdquo;, \u0026ldquo;laparoscopic sleeve gastrectomy\u0026rdquo;, \u0026ldquo;bariatric sleeve surgery\u0026rdquo;, \u0026ldquo;roux-en-y gastric bypass\u0026rdquo;, \u0026ldquo;gastric bypass\u0026rdquo;, \u0026ldquo;RYGB\u0026rdquo;, \u0026ldquo;revisional surgery\u0026rdquo;, \u0026ldquo;conversion surgery\u0026rdquo;, \u0026ldquo;repeat surgery\u0026rdquo;, \u0026ldquo;sleeve to bypass\u0026rdquo;, \u0026ldquo;sleeve gastrectomy to gastric bypass\u0026rdquo;. Studies identified from the search strategy were entered into Covidence (Victoria, Australia) for bibliographic management and duplicates were removed. Two authors, KW and MF independently identified relevant studies, and any discrepancies were resolved by a third reviewed (SB). The exact search strategy has been provided as supplementary material (Sup. 1).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEligibility criteria\u003c/h3\u003e\n\u003cp\u003eThe inclusion and exclusion criteria were defined before the commencement of the literature search. The included studies provided clinical data and outcome rates on women of childbearing age who had undergone bariatric surgery for weight loss with subsequent pregnancy. Bariatric surgery referred to Laparoscopic sleeve gastrectomy (LSG), Roux-en-y gastric bypass (RYGB) or One-anastamosis gastric bypass (OAGB). Eligible study designs included randomised controlled trials (RCT), prospective or retrospective cohort studies, case (control) studies, cross-sectional studies and reviews. Both single-arm and double-arm comparative studies were included. Non-human studies, abstracts, conference presentations, single case reports, editorials and unpublished studies were excluded from the analysis.\u003c/p\u003e\n\u003ch3\u003eQuality assessment\u003c/h3\u003e\n\u003cp\u003eThe quality of studies was assessed using the revised Cochrane's risk of bias tool (RoB2) for RCTs and the Newcastle-Ottawa scale for observational studies without randomisation (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e)\u003c/p\u003e\n\u003ch3\u003eData extraction and handling\u003c/h3\u003e\n\u003cp\u003eA standardised data extraction form was developed on Covidence and the authors AR, CN and JHY independently extracted all relevant data from full text study documents including: study design, sample size, type of bariatric surgery, mean/median maternal BMI (Body mass index), mean incidence of GDM; gestational hypertension, Pre-eclampsia, Pre-term labour, post-partum haemorrhage, anaemia and internal hernia (including SD). Mean APGAR scores, birthweight, gestational age, Neonatal ICU admission rates, Macrosomia, Intra-uterine growth restriction and peri-natal deaths were extracted. Any discrepancy was resolved by an independent reviewer (MF).\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using Stata Software (StataCorp LCC, TX, Version 15.1.) and RevMan (RevMan, Copenhagen: The Nordic Cochrane Centre, the Cochrane Collaboration, 2008). Random effects analysis was used to calculate pooled prevalence estimates for all studies across all outcomes. All studies were included in the meta-analysis if relevant data was available. When studies reported multiple bariatric subgroups, they were separated into distinct categories (e.g., A, B, C) and included as independent entries in the pooled analysis. For studies reporting data for both bariatric and control groups, study effect sizes were combined using odds ratios (OR) along with corresponding 95% confidence intervals (95% CI:) under the random-effects meta-analysis model (inverse variance method). For all results, the DerSimonian and Laird method was applied to account for between-study heterogeneity (I\u003csup\u003e2\u003c/sup\u003e). We considered an I\u003csup\u003e2\u003c/sup\u003e of 30 or less as low, between 30 and 60 to be moderate, and 60 or over as high heterogeneity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eDefinition of outcomes\u003c/h2\u003e \u003cp\u003eThe primary outcomes of interest were divided into maternal and neonatal. Maternal outcomes included: Gestational diabetes, gestational hypertension, pre-eclampsia, pre-term labour, C-section, induction of labour, postpartum haemorrhage, anaemia and internal hernia. Neonatal outcomes included: Apgar scores, birthweight, gestational age, NICU admission rates, macrosomia, intra-uterine growth restriction and perinatal death. Regarding timing of surgery: \u0026lsquo;Early\u0026rsquo; refers to a bariatric surgery conception interval (BSCI) less than 12 months, and \u0026lsquo;Late\u0026rsquo; refers to BSCI greater than 12 months.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStudy Selection\u003c/h2\u003e \u003cp\u003eThe search identified 2468 relevant citations. After removing duplicates, 1809 articles were screened for titles and abstracts, and 231 studies were included for full-text review. Following final screening, 129 studies met the inclusion criteria for quantitative synthesis (Fig.\u0026nbsp;1).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStudy Characteristics\u003c/h2\u003e \u003cp\u003eOf the 129 studies, 110 were retrospective (85.2%) and 19 were prospective (14.7%). Seventeen were multicentre studies and eight were national, with sample sizes ranging from 5 to 66,380 patients. The overall methodological quality of observational studies, assessed using the Newcastle\u0026ndash;Ottawa Scale, was high (80.2%). Poor-quality studies were excluded (Suppl. 2). Among included participants, 45,970 patients (20.2%) had the bariatric procedure type specified, while 181,822 (79.8%) did not differentiate between LSG, RYGB, or OAGB.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003ePatient Characteristics\u003c/h2\u003e \u003cp\u003eMean maternal age ranged from 27.4 years to 38.1 years and the time of conception post bariatric surgery ranged from 1.4 to 92.4 months (IQR 20.3 to 39.9 months).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eMaternal Outcomes\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003eTime to conception\u003c/h2\u003e \u003cp\u003eNinety-three studies reported the interval between surgery and conception, representing 10,644 patients. The pooled mean interval was 29 months (95% CI 27\u0026ndash;32). The weighted mean time from RYGB to conception (1541 patients) was 29.5 months (95% CI 25.1\u0026ndash;34.0), and from LSG (950 patients) was 24.3 months (95% CI 19.1\u0026ndash;29.5).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003ePre-pregnancy weight loss\u003c/h2\u003e \u003cp\u003eThirty-four studies, including 6845 patients, reported BMI before bariatric surgery and at conception. The pooled random-effects analysis demonstrated a mean BMI reduction of 14 kg/m\u0026sup2; (95% CI 13\u0026ndash;15) from pre-surgery to pre-pregnancy.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eGestational weight gain\u003c/h2\u003e \u003cp\u003eGestational weight gain (GWG) was reported in 76 studies involving 11,954 patients with prior bariatric surgery. The random-effects model estimated a pooled mean GWG of 9.66 kg (95% CI 8.53\u0026ndash;10.79).\u003c/p\u003e \u003cp\u003eAcross 21 comparative studies, women with prior bariatric surgery gained less weight during pregnancy compared to obese controls (mean difference \u0026minus;\u0026thinsp;1.17 kg, 95% CI \u0026minus;\u0026thinsp;2.75 to \u0026minus;\u0026thinsp;0.40).\u003c/p\u003e \u003cp\u003eIn procedure-specific analyses, the random-effects weighted mean GWG was 9.33 kg (95% CI 7.79\u0026ndash;10.86) after RYGB (17 studies) and 10.12 kg (95% CI 8.25\u0026ndash;11.99) after LSG (17 studies).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eGestational diabetes (GDM)\u003c/h2\u003e \u003cp\u003eThe prevalence of GDM following bariatric surgery was 11% (95% CI 10\u0026ndash;12) based on 82 studies including 177,926 patients. Across 39 comparative studies, bariatric surgery was associated with a significantly lower risk of GDM compared with obese controls (pooled OR 0.67, 95% CI 0.53\u0026ndash;0.85).\u003c/p\u003e \u003cp\u003eIn 60 studies (21,755 patients) comparing conception intervals, the prevalence of GDM was 8% (95% CI 6\u0026ndash;10) for BSCI\u0026thinsp;\u0026lt;\u0026thinsp;12 months and 8% (95% CI 7\u0026ndash;10) for BSCI\u0026thinsp;\u0026gt;\u0026thinsp;12 months. Comparative analysis across 13 studies found no significant difference between early and late conception groups (OR 0.83, 95% CI 0.57\u0026ndash;1.20).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003ePre-eclampsia\u003c/h2\u003e \u003cp\u003eFifty-four studies, including 171,635 patients, reported on pre-eclampsia, with a pooled prevalence of 5% (95% CI 4\u0026ndash;8). In 27 comparative studies, the odds of pre-eclampsia were significantly lower among women with prior bariatric surgery than among obese controls (OR 0.60, 95% CI 0.45\u0026ndash;0.79).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eMode of delivery \u0026ndash; Caesarean section and Induction of labour\u003c/h2\u003e \u003cp\u003eNinety-five studies including 182,038 patients reported caesarean section rates after bariatric surgery, with a pooled prevalence of 38.6% (95% CI 36.9\u0026ndash;40.3). Across 41 comparative studies, women with prior bariatric surgery had higher odds of caesarean delivery than obese controls (OR 1.24, 95% CI 1.01\u0026ndash;1.52).\u003c/p\u003e \u003cp\u003eInduction of labour was required in 28% of pregnancies after bariatric surgery (95% CI 22\u0026ndash;34), based on 13 studies including 12,820 patients. In 12 comparative studies, women with prior bariatric surgery had higher odds of labour induction (OR 1.34, 95% CI 1.08\u0026ndash;1.66).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003ePostpartum haemorrhage\u003c/h2\u003e \u003cp\u003eFifteen studies (18,615 patients) reported a pooled postpartum haemorrhage rate of 4% (95% CI 4\u0026ndash;5). Sixteen comparative studies showed no significant difference between bariatric and control groups (pooled OR 1.17, 95% CI 0.64\u0026ndash;2.23).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eInternal hernia\u003c/h2\u003e \u003cp\u003eEleven studies including 4578 patients were included in the pooled analysis. The rate of internal herniation after RYGB was 2% (95% CI 1\u0026ndash;4). Eight studies (3680 patients) reported diagnostic laparoscopy rates of 3% (95% CI 1\u0026ndash;5).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eAnaemia and Vitamin deficiencies\u003c/h2\u003e \u003cp\u003eNineteen studies including 4685 patients found a 26% prevalence (95% CI 22\u0026ndash;31) of clinically relevant anaemia after bariatric surgery. Thirty-four studies (872 patients) reported micronutrient deficiencies as follows: zinc 19% (95% CI 11\u0026ndash;27), vitamin A 61% (95% CI 54\u0026ndash;68), vitamin B12 30% (95% CI 21\u0026ndash;39), iron 33% (95% CI 27\u0026ndash;39), calcium 16% (95% CI 8\u0026ndash;23), and vitamin D 69% (95% CI 62\u0026ndash;76). Vitamin A and D deficiencies were the most prevalent, whereas calcium and zinc deficiencies showed wider variation due to smaller sample sizes.\u003c/p\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003eNeonatal outcomes\u003c/h2\u003e \u003cdiv id=\"Sec24\" class=\"Section4\"\u003e \u003ch2\u003eBirthweight\u003c/h2\u003e \u003cp\u003eNinety studies, encompassing 14,204 neonates, reported birthweight. The weighted mean birthweight was 3092 g (95% CI 3056\u0026ndash;3129) after RYGB (3107 neonates) and 3038 g (95% CI 3009\u0026ndash;3068) after LSG (950 neonates). In 29 comparative studies, neonates born to women with prior bariatric surgery had a significantly lower mean birthweight than controls (mean difference \u0026minus;\u0026thinsp;205 g, 95% CI \u0026minus;\u0026thinsp;225 to \u0026minus;\u0026thinsp;186).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003eGestational age\u003c/h2\u003e \u003cp\u003eThirty-two studies reported mean gestational age after RYGB, which included 2746 newborns as 270 days (95% CI: 268\u0026ndash;271). Eleven studies, including 1095 neonates reported mean gestational age after LSG as 269 days (95% CI: 267\u0026ndash;271). There was insufficient data available to perform a stratified analysis of GA for neonates born to mothers with a BSCI\u0026thinsp;\u0026lt;\u0026thinsp;12 months versus \u0026gt;\u0026thinsp;12 months.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e \u003ch2\u003eIntra-uterine growth restriction\u003c/h2\u003e \u003cp\u003eA total of 27 studies involving 72,343 patients reported on intra-uterine growth restriction following bariatric surgery. The pooled effect size was 0.06 (95% CI: 0.05 to 0.07), indicating a low prevalence of 6% for this outcome within the post-surgical population. In the comparative analysis of 13 studies, women with prior bariatric surgery had significantly higher odds of intra-uterine growth restriction compared to controls (OR 2.09, 95% CI: 1.92 to 2.27).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section3\"\u003e \u003ch2\u003eMacrosomia\u003c/h2\u003e \u003cp\u003eA total of 31 studies comprising 17,979 patients reported on macrosomia following bariatric surgery. The pooled effect size was 0.05 (95% CI: 0.04 to 0.07), indicating a low occurrence of macrosomia in this population. However, substantial heterogeneity was observed (I\u0026sup2; = 87.7%).\u003c/p\u003e \u003cp\u003eIn a pooled analysis of 19 studies, women with a history of bariatric surgery had significantly lower odds of delivering a macrosomic neonate compared to controls (OR 0.35, 95% CI: 0.24 to 0.50). Heterogeneity was considerable (I\u0026sup2; = 87%).\u003c/p\u003e \u003cp\u003eThere was insufficient data to perform a stratified analysis according to timing of pregnancy after surgery.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section2\"\u003e \u003ch2\u003ePre-term Birth\u003c/h2\u003e \u003cp\u003eA total of 125 studies, including 121,994 patients, reported on preterm birth among women with prior bariatric surgery. The pooled effect size was 0.10 (95% CI: 0.03\u0026ndash;0.11), corresponding to a prevalence of 10%. Heterogeneity was high (I\u0026sup2; = 85.2%).\u003c/p\u003e \u003cp\u003eIn the comparative analysis of 33 studies, women with a history of bariatric surgery had higher odds of preterm birth compared to controls (OR 1.24, 95% CI: 1.04\u0026ndash;1.47). Heterogeneity across studies was considerable (I\u0026sup2; = 95%), indicating substantial variability in the reported effect estimates.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec29\" class=\"Section2\"\u003e \u003ch2\u003eLow APGAR scores (\u0026lt;\u0026thinsp;7) at 5 minutes\u003c/h2\u003e \u003cp\u003eAmong 10,847 neonates born to mothers with bariatric surgery, the prevalence of low 5-minute APGAR scores was 1.7% (95% CI 1.2\u0026ndash;2.2). Thirteen comparative studies showed higher odds of a low APGAR score in the bariatric group (OR 1.38, 95% CI 1.07\u0026ndash;1.79).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eAdmission to Neonatal Intensive Care Unit (NICU)\u003c/h3\u003e\n\u003cp\u003eSeventy-four studies (11,936 neonates) reported a NICU admission rate of 12% (95% CI 10\u0026ndash;14).\u003c/p\u003e \u003cp\u003eIn 24 comparative studies, neonates of mothers with prior bariatric surgery had higher odds of NICU admission than those of controls (OR 1.39, 95% CI 1.17\u0026ndash;1.65). There was insufficient data to perform a stratified analysis according to timing of pregnancy after surgery.\u003c/p\u003e \u003cdiv id=\"Sec31\" class=\"Section2\"\u003e \u003ch2\u003ePerinatal deaths\u003c/h2\u003e \u003cp\u003eTwelve studies including 66,553 patients reported a pooled perinatal mortality rate of 2% (95% CI 1\u0026ndash;2).\u003c/p\u003e \u003cp\u003eComparative analysis indicated no statistically significant difference in perinatal mortality between groups (OR 1.36, 95% CI 1.00\u0026ndash;1.85).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec32\" class=\"Section2\"\u003e \u003ch2\u003eOther complications\u003c/h2\u003e \u003cp\u003eAnalysis of other significant complications (defined as Clavien-Dindo severity greater than or equal to 3) was pooled from 15 studies including 14727 patients (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Complications with a severity of Clavien-Dindo 3 or higher i.e. those requiring surgical, endoscopic or radiological intervention, intensive care admission or mortality were reported in 5% (95%CI: 4%-7%).\u003c/p\u003e \u003cp\u003e \u003cem\u003eTable\u0026nbsp;1. to be placed here\u003c/em\u003e \u003c/p\u003e \u003cdiv id=\"Sec33\" class=\"Section3\"\u003e \u003ch2\u003eSubgroup Analysis \u0026ndash; Early (\u0026lt;\u0026thinsp;12 months) vs Late (\u0026gt;\u0026thinsp;12 months) pregnancy post-op\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec34\" class=\"Section3\"\u003e \u003ch2\u003eGestational Weight Gain\u003c/h2\u003e \u003cp\u003eIn the early conception group (BSCI\u0026thinsp;\u0026lt;\u0026thinsp;12 months; 483 patients), the weighted mean GWG was 5.24 kg (95% CI 2.04\u0026ndash;8.04). In the late conception group (BSCI\u0026thinsp;\u0026gt;\u0026thinsp;12 months; 3859 patients), it was 10.2 kg (95% CI 9.47\u0026ndash;11.11). Across 15 studies, late conception was associated with significantly greater GWG (mean difference 5.07 kg, 95% CI 2.53\u0026ndash;7.60).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003ePre-term Birth\u003c/h3\u003e\n\u003cp\u003eIn pooled subgroup analysis, the risk of preterm birth was 12% (95% CI 7\u0026ndash;16) in the early pregnancy group and 11% (95% CI 9\u0026ndash;13) in the late group. Comparative analysis of 13 studies found no significant difference between groups (OR 0.88, 95% CI 0.61\u0026ndash;1.27).\u003c/p\u003e \u003cp\u003e \u003cem\u003eFigure 1. to be placed here\u003c/em\u003e \u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cdiv id=\"Sec37\" class=\"Section2\"\u003e \u003ch2\u003eMain findings:\u003c/h2\u003e \u003cp\u003eThis systematic review and meta-analysis revealed reduced odds of developing GDM, pre-eclampsia and fetal macrosomia in pregnancies after BS compared to women with obesity. Conversely, BS was found to be associated with greater odds of undergoing C-section delivery or induction of labour with no significant impact on the odds of post-partum haemorrhage. Conversely, neonates born to women who have undergone BS have higher odds of IUGR, admission to NICU care and Apgars\u0026thinsp;\u0026lt;\u0026thinsp;7 at 5 minutes but with no significant difference in peri-natal mortality.\u003c/p\u003e \u003cdiv id=\"Sec38\" class=\"Section3\"\u003e \u003ch2\u003eMaternal Outcomes\u003c/h2\u003e \u003cp\u003eOur findings confirm that BS is an effective intervention for pre-pregnancy weight loss and significantly reduces average pre-pregnancy BMI. This supports published meta-analyses, which found the reduction in pre-pregnancy BMI (averaging 13.93kg/m2) does not significantly change during early pregnancy and pre-delivery, indicating that weight management is likely to remain stable during pregnancy after initial post-surgery weight loss (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec39\" class=\"Section2\"\u003e \u003ch2\u003eGestational weight gain\u003c/h2\u003e \u003cp\u003eGestational weight gain (GWG) remains a complex issue and is critical for a number of important clinical outcomes, including fetal growth and wellbeing, delivery method, and the risk of weight regain or recurrence of obesity-related co-morbidities. The existing literature links excessive GWG with increased risk of macrosomia, large-for-gestational-age (LGA) infants, caesarean delivery, and GDM, while insufficient GWG correlates with higher risks of IUGR, small-for-gestational-age (SGA) infants, preterm birth, and NICU admissions (\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan additionalcitationids=\"CR23 CR24\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e). Our meta-analysis supports these associations. The prevalence of IUGR was 3% higher in women post-BS compared to women with obesity, whereas macrosomia was 7% less frequent, indicating a trade-off in fetal growth outcomes that requires tailored antenatal monitoring.\u003c/p\u003e \u003cp\u003eThe Institute of Medicine (IOM) provides guidelines based on pre-pregnancy BMI, recommending weight gain of 11.5\u0026ndash;16 kg for women with a normal BMI (18.5\u0026ndash;24.9), 6.8\u0026ndash;11.3 kg for those who are overweight (BMI 25\u0026ndash;29.9), and 5\u0026ndash;9.1 kg for women with obesity (BMI\u0026thinsp;\u0026ge;\u0026thinsp;30) (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e). Our findings suggest women who have undergone BS and reduced pre-pregnancy BMI to \u0026lt;\u0026thinsp;30kg/m\u0026sup2; tend to achieve these targets. Critics of the current IOM guidelines have argued that the weight gain targets are too high, particularly as they do not address concerns regarding post-partum weight retention. Additionally, they do not differentiate between degrees of obesity (Class I to III), which is relevant in the post-bariatric cohort, given that our study found women post-BS have reduced their pre-pregnancy BMI by an average of 14 kg/m\u0026sup2; but may still fall within the broad class of obesity (BMI\u0026thinsp;\u0026gt;\u0026thinsp;30) (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). Furthermore, subgroup analysis demonstrated significantly greater GWG in the late conception group compared to the early conception group (mean difference 5.07 kg), but without significant differences in the odds of GDM or prematurity between subgroups. This finding highlights that maternal weight gain is not the only factor contributing to these observed associations.\u003c/p\u003e \u003cp\u003eFor patients and clinicians, comparing GWG between procedures, our meta-analysis found that women who had undergone RYGB gained slightly less weight during pregnancy (9.33kg) compared to LSG (10.12kg), however with overlapping confidence intervals and high heterogeneity, this difference may not be clinically significant. Previous individual studies reported no difference in GWG between RYGB and SG (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eOverall, our findings underscore that sufficient GWG is necessary for fetal growth, but both inadequate and excessive gain can complicate outcomes in post-bariatric patients. Further IOM guidelines specific for post-bariatric surgery mothers would be useful for clinicians treating this expanding cohort of women.\u003c/p\u003e \u003cdiv id=\"Sec40\" class=\"Section3\"\u003e \u003ch2\u003eGestational Diabetes and Pre-eclampsia\u003c/h2\u003e \u003cp\u003eOur findings support the established literature that BS is associated with significant reduction in major obesity-related pregnancy complications, most notably GDM and pre-eclampsia, compared to obese women without prior BS (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). The prevalence of GDM after BS was 11% based on our findings from the largest known pooled sample in the literature. To contextualize this, the reported pooled global standardized prevalence of GDM is 14% across all pregnancies (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). Thus, BS reduces GDM risk to below the baseline population level. Furthermore, previous meta-analyses demonstrated that the risk of GDM increases with increased BMI in a dose-dependent pattern (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). Thus, our findings support the existing evidence by demonstrating that BS dramatically decreases pre-pregnancy BMI with an expected reduction in the odds of GDM.\u003c/p\u003e \u003cp\u003eWhile the pathophysiology of pre-eclampsia is thought to be linked with abnormal placentation, obesity and excessive weight gain are established risk factors. We found the odds of pre-eclampsia were 40% lower in the bariatric group than in controls. Previous literature has demonstrated similar findings (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThese likely reflect the metabolic improvements attributed to the BRAVE effects described in the literature with the following components: bile flow alteration, reduction in gastric size, anatomical gut rearrangement and altered flow of nutrients, vagal manipulation, and enteric gut modulation (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). Established literature supports remission of diabetes after BS, with RYGB superior in this outcome compared to LSG (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e) and our findings underscore the preventative benefits of RYGB in reducing odds of GDM in pregnancy, through similar metabolic alterations described above.\u003c/p\u003e \u003cp\u003eScreening for GDM in post-bariatric surgery is nevertheless important, and a particular consideration is that standardized oral glucose tolerance testing (OGTT) is often poorly tolerated by women who have undergone procedures like RYGB, LSG and Biliary-pancreatic diversion as these can trigger dumping syndrome (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). Thus, alternative strategies such as multi-point home glucose monitoring and HbA1C may need to be considered (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e\n\u003ch3\u003eDelivery methods\u003c/h3\u003e\n\u003cp\u003eThe mode of delivery was significantly affected by a history of BS, with higher odds of requiring caesarean section and induction of labour in women post-bariatric surgery when compared to obese controls. While this may seem paradoxical it may reflect underlying obstetric risk factors, altered anatomy, or clinical decision-making biases, and the findings warrant further exploration to optimise delivery planning and counselling. Further studies stratifying the urgency of delivery and indications for C-section or labour induction would be beneficial to explore this association. Furthermore, instrumental delivery methods could be included in analysis in future reviews as previous literature has found BS reduces these odds significantly. There was insufficient data to analyze whether delivery methods were impacted by time interval from BS, and further studies would be helpful for both patients and clinicians.\u003c/p\u003e\n\u003ch3\u003ePost surgical complications\u003c/h3\u003e\n\u003cp\u003eOur meta-analysis found that rates of internal hernia after RYGB were low at 2%. And likewise, the rate of diagnostic laparoscopy during pregnancy was 3%. Previous evidence has reported that RYGB presents the greatest risk of surgical complications during pregnancy, with internal herniation occurring in 8% of post-surgical pregnancies and the most common location of the hernia was Petersen's space (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). This is a feared complication and previous reviews found that all maternal and perinatal deaths in pregnancies complicated by internal herniation after RYGB occurred in women treated later than 48 hours after symptom onset. Therefore, despite our findings of a lower incidence than previously reported, a high index of suspicion is required. The presentation may be non-specific, including abdominal pain and vomiting, thus all women of reproductive age undergoing RYGB should be thoroughly counselled on the lifelong risk of this complication to avoid delayed diagnosis and treatment (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). Should clinicians suspect the diagnosis of internal herniation, a multi-disciplinary approach is required when considering the risks versus benefits of diagnostic laparoscopy, CT imaging and even newer modalities such as 3D modelling to confirm diagnosis (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). Ultimately, delays in diagnosis will impact maternal and fetal outcomes, therefore balancing surgical risks, radiation exposure and anaesthetic risks all need careful consideration.\u003c/p\u003e \u003cp\u003eAnother consideration, particularly in pregnancies after LSG is the greater risk of gastro-oesophageal reflux disease (GORD), which already occurs in up to two-thirds of pregnancies (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). While the condition itself is benign, it can significantly affect quality of life and can predispose to Barrett\u0026rsquo;s oesophagus as a pre-malignant condition. In obese women, the effect of pregnancy hormones can exacerbate or cause de novo GORD, particularly in post-surgical mothers who have undergone LSG compared to RYGB (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). Our review of the literature found that papers rarely assessed this maternal outcome, and further studies are needed to analyze the effects of timing of pregnancy after surgery and the differences according to surgery type on GORD incidence, severity and sequelae. While antacids, proton-pump inhibitors and Sucralfate are amongst the medical treatment options, refractory cases may require surgical approaches such as fundoplication, or magnetic sphincter augmentation, but further research is needed regarding the implications of these in pregnancy (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eMaternal nutrition\u003c/h3\u003e\n\u003cp\u003eOur meta-analysis found the overall risk of clinically relevant anaemia to be 26% after all bariatric surgery. Specifically, the prevalence of iron-deficiency in post-surgical patients was 33%, albeit with notable variation between cohorts. The reported global prevalence of anaemia in pregnant women is 36.8%, thus our findings are in keeping with global averages (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). However, it is important to understand the pathophysiology of iron-deficiency anaemia (IDA) in BS, as these patients will have reduced production of hydrochloric acid in the stomach, which is necessary to convert dietary iron in the ferric form into the ferrous state. Furthermore, the reduced intake of meat and the reduction of intestinal iron absorption capacity due to bypassing are other contributors to the observed IDA (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). This can further exacerbate the physiological anaemia observed in pregnancy and certainly requires careful monitoring. Both Vitamin A and D deficiency were demonstrated with a high prevalence of 61% and 69% respectively. This is in keeping with established literature reporting that fat-soluble vitamin deficiencies (A, D, E, K) are common after bariatric surgery due to bypassing absorption sites, reduced bile mixing, and fat malabsorption (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). Vitamin D and A are most affected, with established associations in existing literature to bone, vision, and immune issues (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). Morgan et al. (2025) recently published guidance advising supplementation and blood-test monitoring of these nutrients in each trimester (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). This is essential given the high prevalences found in our study. Specifically regarding vitamin A, these pregnant women should avoid retinol/retinyl esters forms and instead take vitamin A exclusively in the beta‑carotene form under medical supervision to prevent the risks of congenital anomalies (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eNeonatal Outcomes\u003c/h3\u003e\n\u003cp\u003e \u003cb\u003eFetal Growth\u003c/b\u003e \u003c/p\u003e \u003cp\u003eSeveral important trends emerged in neonatal outcomes. As discussed above, infants born to mothers with prior BS had greater odds of IUGR and preterm birth. These findings support the hypothesis that rapid maternal weight loss and nutritional deficits may adversely affect fetal growth. Conversely, our study found that BS significantly reduced the odds of macrosomia, which is an expected benefit in this population based on existing literature. Overall, we found neonates born to women after BS weighed over 200g less than neonates born to obese mothers. This finding is consistent with previous meta-analyses in the literature (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). These findings underscore the importance of antenatal nutritional monitoring, targeted supplementation and adherence to GWG targets, particularly in mothers who are within 12 months of BS who may be at greater risk for anemia and fat-soluble vitamin deficiencies described above.\u003c/p\u003e\n\u003ch3\u003eAPGAR scores, NICU admissions and peri-natal mortality\u003c/h3\u003e\n\u003cp\u003eNICU admission rates (12%) and low Apgar scores\u0026thinsp;\u0026lt;\u0026thinsp;7 at 5 min (1.7%) were both slightly elevated in the bariatric surgery cohort. While these rates were modest, they reflect a need for heightened neonatal surveillance and underscore the importance of coordinated perinatal care. These variables may also reflect the confounding effects of both IUGR and prematurity on the risk of NICU admission.\u003c/p\u003e \u003cp\u003eAdopting a nuanced approach in this obstetric population may be prudent because although the odds of preterm birth did not significantly differ between early and late groups, there remains insufficient data on whether timing of pregnancy after BS correlates with IUGR, admission to NICU or perinatal mortality. More studies are needed to clarify the impact of BS on these critical clinical outcomes, perhaps modeling the time-interval from surgery to pregnancy as a continuous variable rather than a dichotomous cut-off.\u003c/p\u003e \u003cp\u003eImportantly, perinatal mortality rates were low (0.2%) and not significantly different between neonates born to women post-bariatric surgery compared to obese mothers, providing reassurance regarding overall fetal viability. A previous meta-analysis by Akhter et al. (2019) found the odds of peri-natal mortality to be increased after BS (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). However, our results border on statistical significance and may nevertheless justify heightened clinical vigilance.\u003c/p\u003e\n\u003ch3\u003eTiming of Conception Post-Surgery\u003c/h3\u003e\n\u003cp\u003eSubgroup analyses based on time interval to conception (\u0026lt;\u0026thinsp;12 months vs. \u0026gt;12 months post-bariatric surgery) provided valuable clinical insights; however, their interpretation is constrained by heterogeneity across studies and limited sample sizes. Early conception within 12 months was associated with lower GWG, a non-significant increased odd of preterm birth, and no appreciable difference in the odds of GDM compared to later conception. These findings lend cautious support to current clinical guidelines recommending a minimum 12-month interval before conception to promote metabolic stabilisation and mitigate nutritional risks, which may be higher if the rapid weight loss phase post-surgery overlaps with early pregnancy. Nonetheless, future research should consider modeling time to conception as a continuous variable to better capture its relationship with maternal and neonatal outcomes, and to offer more nuanced guidance for clinical decision-making.\u003c/p\u003e\n\u003ch3\u003eStudy Quality and Limitations\u003c/h3\u003e\n\u003cp\u003eThe strength of this study includes the large pool of articles included in the original search. However, high heterogeneity in several analyses result from variability in study design, population characteristics, and surgical techniques, affecting generalizability. The limitations include the lack of RCTs and prospective data collection, smaller case-series, large heterogeneity in some analysis, unmeasured confounders and limited studies comparing early versus late conception at consistent intervals.\u003c/p\u003e \u003cp\u003eLack of detailed data on nutritional status and micronutrient deficiencies stratified according to pregnancy timing and surgery type limits recommendations for post-bariatric surgery pregnancies. Reduced opportunity to conduct randomized controlled trials in this population limits evidence strength, relying on observational studies.\u003c/p\u003e \u003cp\u003eMost included studies were retrospective in nature (85.2%), introducing potential for selection, recall and reporting bias, confounding variables, and missing data. Although study quality was generally high per the Newcastle-Ottawa Scale, heterogeneity across outcomes was considerable (I\u0026sup2; \u0026gt; 80% in many analyses), reflecting variation in patient characteristics, surgical procedures, definitions of outcomes, and follow-up protocols.\u003c/p\u003e \u003cp\u003eImportantly, many studies did not differentiate between specific types of bariatric procedures (e.g., LSG vs. RYGB), limiting the ability to draw procedure-specific conclusions. Given the distinct anatomical and absorptive alterations associated with different surgeries, future research should stratify by surgery type to enable more nuanced guidance.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis systematic review and meta-analysis demonstrates that BS prior to pregnancy significantly reduces the risk of obesity-related complications such as gestational diabetes, pre-eclampsia, and fetal macrosomia. However, BS is also associated with increased odds of caesarean delivery, labour induction, intrauterine growth restriction, NICU admission, and low Apgar scores, highlighting a complex balance of maternal and neonatal risks.\u003c/p\u003e \u003cp\u003eThe substantial heterogeneity across studies reflects variations in surgical procedures, patient characteristics, and timing of conception, highlighting the importance of individualised care, multidisciplinary antenatal management, and robust preconception counselling. Nutritional deficiencies, particularly in iron and fat-soluble vitamins, were frequent and warrant vigilant monitoring and supplementation throughout pregnancy.\u003c/p\u003e \u003cp\u003e These findings support current guidelines recommending delayed conception for at least 12 months post-surgery to allow for nutritional stabilisation but emphasise the need for gestational weight gain guidelines tailored to this population. Critically, this review identifies key evidence gaps, including the need for high-quality prospective studies and refined analyses that model time from surgery to pregnancy as a continuous variable to account for the nuances of individual variation in weight stabilisation and better risk stratification. Addressing these gaps will advance clinical practice and support safer, more tailored care for women navigating pregnancy after bariatric surgery.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eContributor and guarantor information\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe study was conceived by MF and designed by MF, WL MK, YAA. The data was acquired and collated by MF, AR, CN, JHY, KW, SB and analysed by KW, SB, MF. The manuscript was drafted and revised critically for important intellectual content by all authors. All authors gave final approval of the version to be published. The corresponding author (MF) attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted. The guarantor (MF) accepts full responsibility for the work, had access to the data, and controlled the decision to publish.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNo external funding was received for this study\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest declaration\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest with regards to the presented work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and patient consent\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEthical approval was not required for this systematic review and meta-analysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data relevant to the study are included in the article or uploaded as supplementary information\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTransparency declaration\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe lead author (KW) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained. All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organisations.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePatient Involvement and Dissemination\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe research questions and outcomes were formulated based on patients' concerns and priorities. While patients were not directly involved in interpreting results or writing the article, efforts will be made to share findings with the lay audience through various channels, including press releases, social media, and authors' engagements with charities, public presentations and interviews.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eYu Y, Ma Q, Groth SW. Risk factors for preterm birth in pregnancies following bariatric surgery: an analysis of the Longitudinal Assessment of Bariatric Surgery-2. Surg Obes Relat Dis. 2022;18(11):1304\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSlack E, Best KE, Rankin J, Heslehurst N. Maternal obesity classes, preterm and post-term birth: a retrospective analysis of 479,864 births in England. BMC Pregnancy Childbirth. 2019;19(1):434.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSheiner E, Balaban E, Dreiher J, Levi I, Levy A. Pregnancy Outcome in Patients Following Different Types of Bariatric Surgeries. Obes Surg. 2009;19(9):1286\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSheiner E, Edri A, Balaban E, Levi I, Aricha-Tamir B. Pregnancy outcome of patients who conceive during or after the first year following bariatric surgery. Am J Obstet Gynecol. 2011;204(1):50.e1-50.e6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang YH, Wu HH, Ding H, Li Y, Wang ZH, Li F, et al. Changes of insulin resistance and β-cell function in women with gestational diabetes mellitus and normal pregnant women during mid- and late pregnant period: a case-control study. J Obstet Gynaecol Res. 2013;39(3):647\u0026ndash;52.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang H, Li N, Chivese T, Werfalli M, Sun H, Yuen L, et al. IDF Diabetes Atlas: Estimation of Global and Regional Gestational Diabetes Mellitus Prevalence for 2021 by International Association of Diabetes in Pregnancy Study Group\u0026rsquo;s Criteria. Diabetes Res Clin Pract. 2022;183:109050.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarchi J, Berg M, Dencker A, Olander EK, Begley C. Risks associated with obesity in pregnancy, for the mother and baby: a systematic review of reviews. Obes Rev. 2015;16(8):621\u0026ndash;38.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePoston L, Caleyachetty R, Cnattingius S, Corval\u0026aacute;n C, Uauy R, Herring S, et al. Preconceptional and maternal obesity: epidemiology and health consequences. Lancet Diabetes Endocrinol. 2016;4(12):1025\u0026ndash;36.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKourlaba G, Relakis J, Kontodimas S, Holm MV, Maniadakis N. A systematic review and meta-analysis of the epidemiology and burden of venous thromboembolism among pregnant women. Int J Gynecol Obstet. 2016;132(1):4\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMart\u0026iacute;nez-Hortelano JA, Cavero-Redondo I, \u0026Aacute;lvarez-Bueno C, Garrido-Miguel M, Soriano-Cano A, Mart\u0026iacute;nez-Vizca\u0026iacute;no V. Monitoring gestational weight gain and prepregnancy BMI using the 2009 IOM guidelines in the global population: a systematic review and meta-analysis. BMC Pregnancy Childbirth. 2020;20(1):649.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEdison E, Whyte M, van Jones VJ, de Gatenby S. Bariatric Surgery in Obese Women of Reproductive Age Improves Conditions That Underlie Fertility and Pregnancy Outcomes: Retrospective Cohort Study of UK National Bariatric Surgery Registry (NBSR). Obes Surg. 2016;26(12):2837\u0026ndash;42.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFehervari M, Banh S, Varma P, Das B, Al-Yaqout K, Al-Sabah S, et al. Weight loss specific to indication, remission of diabetes, and short-term complications after sleeve gastrectomy conversion to Roux-en-Y gastric bypass: a systematic review and meta-analysis. Surg Obes Relat Dis. 2023;19(4):384\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMeek CL, Lewis HB, Reimann F, Gribble FM, Park AJ. The effect of bariatric surgery on gastrointestinal and pancreatic peptide hormones. Peptides. 2016;77:28\u0026ndash;37.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaggard MA, Yermilov I, Li Z, Maglione M, Newberry S, Suttorp M, et al. Pregnancy and fertility following bariatric surgery: a systematic review. JAMA. 2008;300(19):2286\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGalazis N, Docheva N, Simillis C, Nicolaides KH. Maternal and neonatal outcomes in women undergoing bariatric surgery: a systematic review and meta-analysis. Eur J Obstet Gynecol Reprod Biol. 2014;181:45\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJohansson K, Cnattingius S, N\u0026auml;slund I, Roos N, Trolle Lagerros Y, Granath F, et al. Outcomes of Pregnancy after Bariatric Surgery. N Engl J Med. 2015;372(9):814\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrandfils S, Demondion D, Kyheng M, Duhamel A, Lorio E, Pattou F, et al. Impact of gestational weight gain on perinatal outcomes after a bariatric surgery. J Gynecol Obstet Hum Reprod. 2019;48(6):401\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStephansson O, Johansson K, S\u0026ouml;derling J, N\u0026auml;slund I, Neovius M. Delivery outcomes in term births after bariatric surgery: Population-based matched cohort study. Myers JE, editor. PLOS Med. 2018;15(9):e1002656.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDevlieger R, Guelinckx I, Jans G, Voets W, Vanholsbeke C, Vansant G. Micronutrient Levels and Supplement Intake in Pregnancy after Bariatric Surgery: A Prospective Cohort Study. PLoS ONE. 2014;9(12):e114192.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaslin K, James A, Brown A, Bogaerts A, Shawe J. What Is Known About the Nutritional Intake of Women during Pregnancy Following Bariatric Surgery? A Scoping Review. Nutrients. 2019;11(9):2116.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJans G, Guelinckx I, Voets W, Galjaard S, Van Haard PMM, Vansant GM, et al. Vitamin K1 monitoring in pregnancies after bariatric surgery: a prospective cohort study. Surg Obes Relat Dis. 2014;10(5):885\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShawe J, Ceulemans D, Akhter Z, Neff K, Hart K, Heslehurst N, et al. Pregnancy after bariatric surgery: Consensus recommendations for periconception, antenatal and postnatal care. Obes Rev Off J Int Assoc Study Obes. 2019;20(11):1507\u0026ndash;22.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCiangura C, Coupaye M, Deruelle P, Gascoin G, Calabrese D, Cosson E, et al. Clinical Practice Guidelines for Childbearing Female Candidates for Bariatric Surgery, Pregnancy, and Post-partum Management After Bariatric Surgery. Obes Surg. 2019;29(11):3722\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeusschen L, Krabbendam I, Van Der Velde JM, Deden LN, Aarts EO, Meri\u0026eacute;n AER, et al. A Matter of Timing\u0026mdash;Pregnancy After Bariatric Surgery. Obes Surg. 2021;31(5):2072\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarreira A, Ara\u0026uacute;jo B, Lavrador M, Vieira I, Rodrigues D, Paiva S, et al. From Bariatric Surgery to Conception: The Ideal Timing to Optimize Fetal Weight. Obes Surg. 2023;33(9):2859\u0026ndash;65.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSterne JAC, Savović J, Page MJ, Elbers RG, Blencowe NS, Boutron I et al. RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ. 2019;l4898.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWells G, Wells G, Shea B, Shea B, O\u0026rsquo;Connell D, Peterson J et al. The Newcastle-Ottawa Scale (NOS) for Assessing the Quality of Nonrandomised Studies in Meta-Analyses. In 2014 [cited 2025 Jan 22]. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.semanticscholar.org/paper/The-Newcastle-Ottawa-Scale-(NOS)-for-Assessing-the-Wells-Wells/c293fb316b6176154c3fdbb8340a107d9c8c82bf\u003c/span\u003e\u003cspan address=\"https://www.semanticscholar.org/paper/The-Newcastle-Ottawa-Scale-(NOS)-for-Assessing-the-Wells-Wells/c293fb316b6176154c3fdbb8340a107d9c8c82bf\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDindo D, Demartines N, Clavien PA. Classification of Surgical Complications. Ann Surg. 2004;240(2):205\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCeulemans D, De Mulder P, Lebbe B, Coppens M, De Becker B, Dillemans B, et al. Gestational weight gain and postpartum weight retention after bariatric surgery: data from a prospective cohort study. Surg Obes Relat Dis. 2021;17(4):659\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMorgan HD, Morrison AE, Hamza M, Jones C, Cassar CB, Meek CL. The approach to a pregnancy after bariatric surgery. Clin Med. 2024;25(1):100275.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChu SY, Callaghan WM, Kim SY, Schmid CH, Lau J, England LJ, et al. Maternal obesity and risk of gestational diabetes mellitus. Diabetes Care. 2007;30(8):2070\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRobb HD, Arif A, Narendranath RM, Das B, Alyaqout K, Lynn W, et al. How is 3D modeling in metabolic surgery utilized and what is its clinical benefit: a systematic review and meta-analysis. Int J Surg Lond Engl. 2025;111(5):3159\u0026ndash;68.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAltuwaijri M. Evidence-based treatment recommendations for gastroesophageal reflux disease during pregnancy: A review. Med (Baltim). 2022;101(35):e30487.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSargsyan N, Ali I, Namgoong C, Das B, Fehervari M, Fadel MG. Gastro-Oesophageal Reflux Disease Outcomes Following Roux-en-Y Gastric Bypass Surgery in Patients with Obesity: A Systematic Review and Meta-analysis. Obes Surg. 2025;35(6):2321\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFadel MG, Tarazi M, Dave M, Reddy M, Khan O, Fakih-Gomez N, et al. Magnetic sphincter augmentation in the management of gastro-esophageal reflux disease: a systematic review and meta-analysis. Int J Surg Lond Engl. 2024;110(10):6355\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKarami M, Chaleshgar M, Salari N, Akbari H, Mohammadi M. Global Prevalence of Anemia in Pregnant Women: A Comprehensive Systematic Review and Meta-Analysis. Matern Child Health J. 2022;26(7):1473\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMechanick JI, Youdim A, Jones DB, Garvey WT, Hurley DL, McMahon M, et al. Clinical Practice Guidelines for the Perioperative Nutritional, Metabolic, and Nonsurgical Support of the Bariatric Surgery Patient\u0026mdash;2013 Update: Cosponsored by American Association of Clinical Endocrinologists, The Obesity Society, and American Society for Metabolic \u0026amp; Bariatric Surgery. Obes Silver Spring Md. 2013;21(0 1):S1\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeber D, Greenway FL, Kaplan LM, Livingston E, Salvador J, Still C, et al. Endocrine and nutritional management of the post-bariatric surgery patient: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2010;95(11):4823\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAkhter Z, Rankin J, Ceulemans D, Ngongalah L, Ackroyd R, Devlieger R, et al. Pregnancy after bariatric surgery and adverse perinatal outcomes: A systematic review and meta-analysis. PLoS Med. 2019;16(8):e1002866.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArbis A, Rafay A, Namgoong C, Yoon JH, Ashrafian H, Fehervari M et al. The impact of bariatric surgery on maternal and neonatal health: a systematic review and meta-analysis. Surg Obes Relat Dis Off J Am Soc Bariatr Surg. 2025;S1550-7289(25)00112-1.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Table 1","content":"\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Summary of maternal and neonatal outcomes following bariatric Surgery: pooled proportions and comparative meta-analysesh\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"602\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" style=\"width: 602px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePooled Outcome Rates in Women with a History of Bariatric Surgery\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 263px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOutcome\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo. of Studies (n)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEffect Estimate (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eGestational weight gain (kg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e106\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e9.66 [8.53, 10.79]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eGestational diabetes (GDM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.11 [0.10, 0.12]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePre-eclampsia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.05 [0.04, 0.08]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eCaesarean section\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.39 [0.37, 0.40]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eInduction of labour\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.28 [0.22, 0.34]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePostpartum haemorrhage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.04 [0.04, 0.05]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eNICU admission\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.12 [0.10, 0.14]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePreterm birth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.101 [0.03, 0.11]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eIntrauterine growth restriction (IUGR)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.06 [0.05, 0.07]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eMacrosomia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.05 [0.04, 0.07]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eLow APGAR (\u0026lt;7 at 5 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.02 [0.01, 0.02]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eAnaemia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.26 [0.22, 0.31]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eVitamin deficiencies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.04 [0.03, 0.05]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eInternal hernia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.02 [0.01, 0.04]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eDiagnostic laparoscopy (hernia)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.03 [0.01, 0.05]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\" style=\"width: 602px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComparative Outcomes: Bariatric Surgery vs. Non-Surgical Controls\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 263px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOutcome\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 129px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo. of Studies (n)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOR/Mean Difference (95% CI)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eGestational weight gain\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e\u0026ndash;1.17 kg [\u0026ndash;2.75, 0.40]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eGestational diabetes (GDM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.67 [0.53, 0.85]***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePre-eclampsia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.60 [0.45, 0.79]***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eCaesarean section\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.24 [1.01, 1.52]*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eInduction of labour\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.34 [1.08, 1.66]**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePostpartum haemorrhage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.17 [0.64, 2.23]\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eNICU admission\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.39 [1.17, 1.65]**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePreterm birth\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.24 [1.04, 1.47]*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eBirthweight\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e\u0026ndash;205.38 [\u0026ndash;224.86, \u0026ndash;185.90]***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eIUGR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e2.09 [1.92, 2.27]***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eMacrosomia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e0.35 [0.24, 0.50]***\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003eLow APGAR (\u0026lt;7 at 5 min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e1.38 [1.07, 1.79]**\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 263px;\"\u003e\n \u003cp\u003ePerinatal deaths\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 129px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 210px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ePooled estimates were derived using a DerSimonian\u0026ndash;Laird random effects model. Proportions represent pooled single-arm event rates among women with a history of bariatric surgery. Comparative estimates (ORs or mean differences) reflect outcome differences between bariatric surgery and non-surgical control groups. Studies reporting multiple surgical subgroups were included separately in pooled estimates if data were stratified. *p-value\u0026lt;0.05, ** p-value\u0026lt;0.01, *** p-value\u0026lt;0.001.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Pregnancy, peripartum, perinatal, maternal, gestational, postpartum, postnatal, antenatal, neonate, neonatal, newborn, baby, babies, foetal outcomes, bariatric surgery, weight loss surgery, obesity, gastric bypass, sleeve gastrectomy, Roux-en-Y, laparoscopic bypass risks ","lastPublishedDoi":"10.21203/rs.3.rs-8723438/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8723438/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction:\u003c/strong\u003e\u003cbr\u003e\nBariatric surgery (BS) is an increasingly common intervention for women of reproductive age with morbid obesity, however the optimal timing of pregnancy following surgery has not yet been fully established, particularly as it impacts both obstetric and neonatal outcomes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003cbr\u003e\nSystematic search of Medline, EMBASE, EMCARE, and Cochrane databases identified 2468 studies for screening; 129 met inclusion criteria. The meta-analysis included women who underwent various BS procedures followed by pregnancy. Outcomes were analyzed using a random-effects model, comparing early (\u0026lt;12 months) and later (\u0026gt;12 months) post-surgery conception. Maternal outcomes included gestational weight gain (GWG), gestational diabetes (GDM), pre-eclampsia, preterm birth, caesarean delivery, induction of labour, postpartum hemorrhage (PPH), anaemia, and internal hernia.\u0026nbsp; Neonatal outcomes included Apgar scores, birthweight, gestational age, Neonatal intensive care unit (NICU) admissions, macrosomia, intrauterine growth restriction (IUGR), and perinatal death.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eBariatric surgery reduced pre-pregnancy BMI by 14\u0026nbsp;kg/m² (95% CI: 13– 15kg/m\u003csup\u003e2\u003c/sup\u003e, I² = 93.1%, p=0.000). Postoperative pregnancies had lower odds of gestational diabetes (OR 0.67, 95% CI: 0.53–0.85), pre-eclampsia (OR 0.60, 95% CI: 0.45–0.79), and macrosomia (OR 0.35, 95% CI: 0.24–0.50), but higher odds of intrauterine growth restriction (OR 2.09, 95% CI: 1.92–2.27), prematurity (OR 1.24, 95% CI: 1.04-1.47) and NICU admission (OR 1.39, 95% CI: 1.17–1.65). Mean GWG in women who conceived within 12 months of BS was 5.2kg (95% CI: 2.0, 8.0), compared to 10.2 (95% CI: 9.5, 11,1) in women who conceived \u0026gt;12 months after BS. PPH and caesarean rates were similar between post-BS pregnancies and obese controls. The prevalence rate of anaemia was 26% (95% CI: 22–31) and Vitamin D deficiency was 69.0% (95% CI: 61.8, 76.2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003cbr\u003e\nBariatric surgery reduces obstetric risks of GDM, hypertensive disorders, and macrosomia. However, conception within 12 months is associated with lower GWG. BS increased odds of IUGR and preterm birth without significant difference in peri-natal mortality. Nutritional deficiencies, including anaemia, and fat-soluble vitamins, require close monitoring, particularly in early post-surgical pregnancies.\u003c/p\u003e","manuscriptTitle":"Impact of Bariatric Surgery on Pregnancy: A Systematic Review and Meta-analysis ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-18 08:38:49","doi":"10.21203/rs.3.rs-8723438/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-03-13T14:40:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-13T13:38:12+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-10T10:41:35+00:00","index":"","fulltext":""},{"type":"submitted","content":"Obesity Surgery","date":"2026-01-28T15:51:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"obesity-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"obsu","sideBox":"Learn more about [Obesity Surgery](https://link.springer.com/journal/11695)","snPcode":"11695","submissionUrl":"https://submission.springernature.com/new-submission/11695/3","title":"Obesity Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"5cb0e0cc-9086-44df-898f-5932be64d68d","owner":[],"postedDate":"March 18th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-18T08:38:51+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-18 08:38:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8723438","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8723438","identity":"rs-8723438","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}