{"paper_id":"e958a7dd-766d-40e9-8ed6-c90f5aacd858","body_text":"Shoukry et al. \nMiddle East Fertility Society Journal           (2024) 29:41  \nhttps://doi.org/10.1186/s43043-024-00200-x\nRESEARCH\nReproductive outcomes in women \nwith advanced endometriosis in fresh \nversus frozen embryo transfer cycles\nAhmed Shoukry1*  , Wael Samir El Gazeirly1, Mohamed Abdelkader Khattab2 and \nHesham Mahmoud Adel Abdelmoneim1 \nAbstract \nBackground ART in women with endometriosis is associated with poor quality of the retrieved oocytes and lower \nfertilization and pregnancy rates, reflecting that endometriosis may influence fertility by altering the quality \nof both the oocyte and embryo quality and also by impairing the endometrial receptivity. On comparing endometri-\nosis-affected patients to healthy counterparts, many differences were demonstrated at the endometrial level. Thus, \nchoosing the appropriate method of embryo transfer is of utmost importance, particularly for patients with advanced \nendometriosis.\nObjective The aim of the present study was to compare the reproductive outcomes between fresh and frozen \nembryo transfer cycles in women with advanced endometriosis.\nMaterial and methods A retrospective cohort study was conducted in the period from January 2018 until Decem-\nber 2021 for patients recruited from two IVF centers, Alexandria, Egypt. Careful review of paper and electronic \nmedical records of infertile women (primary, relative, or secondary infertility) aged 18–37 years who were diagnosed \nwith advanced endometriosis by means of laparoscopy and were scheduled for ICSI followed by either fresh embryo \ntransfer (group I) or freeze-all embryos and deferred embryo transfer (group II) of day 5 embryo(s) was included \nin the study.\nResults Two-hundred and eleven women were eligible and included in the study. Women in each study group were \nmatched regarding baseline characteristics. Clinical pregnancy, implantation, and ongoing pregnancy rates were sta-\ntistically significantly higher in the group of frozen embryo transfer (p < 0.001). Miscarriage rate was found to be higher \nin the group of fresh transfer compared to FET group but without a statistical significance (20.9% vs 9.2%, p = 0.072).\nConclusion In women with advanced endometriosis, freeze-all policy seems to be associated with better implanta-\ntion, ongoing pregnancy rates.\nKeywords Endometriosis, Freeze all, Frozen embryo transfer, Ongoing pregnancy rate\nIntroduction\nEndometriosis is defined as a disease characterized by \nthe presence of endometrium resembling epithelium \nand/or stroma outside the endometrium and myome -\ntrium, usually in association with an inflammatory pro -\ncess [1]. It roughly affects 10% (approximately 190 million \nwomen worldwide) of girls and women of reproductive \nage globally.\nOpen Access\n© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which \npermits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the \noriginal author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or \nother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line \nto the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory \nregulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this \nlicence, visit http://creativecommons.org/licenses/by/4.0/.\nMiddle East Fertility\nSociety Journal\n*Correspondence:\nAhmed Shoukry\nahmedshoukry1989@outlook.com\n1 Obstetrics and Gynecology, Department of Obstetrics and Gynecology, \nFaculty of Medicine, Alexandria University, Alexandria, Egypt\n2 Obstetrics and Gynecology, Alexandria University Hospitals, Alexandria, \nEgypt\n\nPage 2 of 8Shoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \nEndometriosis-infertility relationship has been a point \nof debate for decades. The fecundity ranges from 15 to \n20% per month in normal couples and declines with age. \nPatients with endometriosis have a decreased monthly \nfecundity of about 0.2–1% each month [2, 3]. Moreover, \nendometriosis is associated with decline in the live birth \nrate (LBR) [4]. Although ART remain the most effective \ntreatment modality for infertile women with endometrio-\nsis, it still yields poor outcomes as ART could not over -\ncome all the substantial effects of endometriosis [5, 6]. \nEndometriosis-affected women have declined pregnancy \nand implantation rates in comparison to women without \nendometriosis [7].\nIt was noticed that endometriosis has undesirable \neffect on the pregnancy, miscarriage, and live birth rates. \nIt was found that ART outcomes, as the quality of the \nretrieved oocytes and fertilization rate, are negatively \ninfluenced by the existence of endometriosis, reflect -\ning that endometriosis influence fertility by altering the \nquality of both the oocyte and embryo quality and by \nimpairing the endometrial receptivity [6]. On comparing \nendometriosis-affected patients to healthy counterparts, \nmany differences were demonstrated at the endometrial \nlevel [8], which define the decline in the receptivity of the \nendometrium. Thus, choosing the appropriate method of \nembryo transfer is of utmost importance, particularly for \npatients with advanced endometriosis.\nIn the view of the impact of the supraphysiological level \nof hormones associated with stimulation in fresh embryo \ntransfer on the uterine environment during early peri-\nimplantation, it was demonstrated that flowing of blood \nin the endometrium and sub-endometrium is reduced \nin stimulated cycles in comparison to natural cycles as \nevaluated by three-dimensional power Doppler ultra -\nsonography [9]. Furthermore, histopathologic alterations \nof the stimulated endometrium were reported, and this \nincludes advancement in the maturation of the endome -\ntrium [10] and premature development of channel sys -\ntems in the nucleolus [11].\nOn the other hand, in frozen embryo transfer (FET) \ncycles, endometrial growth can be more controlled than \nin fresh cycles [12]. Based on that, the use of frozen \nembryos avoided the supraphysiological hormone level \nfound during ovarian hyperstimulation in in vitro fertili -\nzation (IVF)/ICSI with fresh embryo transfer, which leads \nto an unfavorable environment for implantation and has \nbeen found to have detrimental effects on the endome -\ntrial receptivity, irrespective of the amount of retrieved \noocytes or levels of progesterone (P) [13–16].\nTherefore, the aim of the present study was to com -\npare the reproductive outcomes between fresh and fro -\nzen embryo transfer cycles in women with advanced \nendometriosis.\nStudy design and setting\nA retrospective cohort study was conducted in the \nperiod from January 2018 until December 2021 for \npatients recruited from two IVF centers (Agial Fertility \nCenter & Dar-Elkhosoba Center), Alexandria, Egypt.\nMaterials and methods\nCareful review of paper and electronic medical records \nof infertile women (primary, relative, or secondary \ninfertility) aged 18–37 years who were diagnosed with \nadvanced endometriosis, stage III/IV r-ASRM clas -\nsification [17], by means of laparoscopy and were \nscheduled for intracytoplasmic sperm injection (ICSI) \nfollowed by either fresh embryo transfer or freeze-\nall embryos and deferred embryo transfer of day 5 \nembryo(s) was included in the study.\nCouples with abnormal semen analysis of the male \npartner, recurrent implantation failure in previous ICSI \ntrials, and women with uterine lesions such as fibroids, \nadenomyosis, polypi, uterine septum, and women with \nno available follow up data were excluded from the \nstudy. The study protocol was approved from the Eth -\nics Committee of Faculty of Medicine, Alexandria \nUniversity.\nOvarian stimulation\nAll the women enrolled in the study underwent con -\ntrolled ovarian stimulation via the fixed GnRH antago -\nnist protocol. Before ovarian stimulation, women were \npretreated with combined oral contraceptive pills for \n2–3 weeks. On day 2 of the menstrual cycle (stimula -\ntion day 1), patients received a fixed daily dose of recom -\nbinant FSH or combination of rec-FSH and human \nmenopausal gonadotropins. Starting on day 5 of stimu -\nlation, patients underwent monitoring with transvaginal \nultrasound and serial assessment of estradiol every 2–3 \ndays as required. A daily subcutaneous dose of 0.25 mg \nof GnRH antagonist cetrorelix was initiated on day 6 of \novarian stimulation and continued up to the day of trig -\nger administration. When at least three follicles reached \n17 mm in diameter, final oocyte maturation was trig -\ngered using 10,000 IU of human chorionic gonadotropin \n(hCG). Ovum pickup (OPU) was performed 35–36 h of \nhCG administration. Mature oocytes were inseminated \nby means of intracytoplasmic sperm injection and cul -\ntured to blastocyst stage.\nGroup I: Women who underwent fresh embryo transfer (ET)\nCombined vaginal suppositories (400 mg twice daily) \nand intramuscular progesterone in oil (50 mg once daily) \n\nPage 3 of 8\nShoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \n \ninjections were started on day of OPU, and ET was per -\nformed 5 days after P administration.\nGroup II: Women who underwent frozen embryo \ntransfer after endometrial preparation through artificial \nor programmed cycle\nAfter vitrification of the available embryos, in the sub -\nsequent cycle, women underwent ovarian suppression \nby combined pills for 2–3 weeks, and then endometrial \npreparation was achieved with a daily dose of 8 mg of \nestradiol valerate for at least 12–14 days. When endome -\ntrium thickness was at least 8 mm and E2 level reached \nat least 200 pg/dl, progesterone as vaginal suppositories \n(400 mg twice daily) and intramuscular in oil (50 mg \nonce daily) injection was administered, and ET of thawed \nembryos was performed after 5 days of P therapy.\nOutcome variables\nThe primary outcome of the study was the ongoing \npregnancy rate (OPR) defined as pregnancy progressed \nbeyond 14 weeks’ gestation. Secondary outcomes include \nthe following: implantation rate, defined as the num -\nber of intrauterine gestational sacs observed by trans -\nvaginal ultrasound divided by the number of transferred \nembryos; clinical pregnancy rate (CPR), calculated by \nconsidering clinical pregnancy and determined by the \nvisualization of a viable gestational sac within the uter -\nine cavity by ultrasound 3–4 weeks after embryo transfer; \nand miscarriage rate, defined as the number of cases who \naborted (after a confirmed clinical pregnancy) divided by \nthe total number of pregnant cases.\nStatistical analysis\nData were fed to the computer and analyzed using IBM \nSPSS software package version 20.0. (Armonk, NY: IBM \nCorp.). Qualitative data were described using number \nand percent. The Kolmogorov-Smirnov test was used to \nverify the normality of distribution. Quantitative data \nwere described using range (minimum and maximum), \nmean, standard deviation, median, and interquartile \nrange (IQR). Significance of the obtained results was \njudged at the 5% level. The used tests were chi-square test \nfor categorical variables, to compare between different \ngroups; Student t-test for normally distributed quantita -\ntive variables, to compare between two studied groups; \nand Mann-Whitney test for abnormally distributed \nquantitative variables, to compare between two studied \ngroups.\nResults\nOver the 4-year study period, there were 237 women with \nadvanced endometriosis who underwent either fresh or \nfrozen embryo transfer cycles; out of them, 211 women \nwere eligible and included in the study, and Fig.  1 dem-\nonstrates the flow chart of the study. The study included \n211 patients divided into two groups as follows: Group \nI includes 103 patients who underwent fresh embryo \ntransfer, and Group II includes 108 patients who under -\nwent frozen embryo transfer.\nRegarding the baseline characteristics of both groups \n(Table 1), patients in the two study groups were matched \nregarding mean age, infertility duration, type of infertil -\nity (primary or secondary), body mass index, and AMH \nlevel.\nFig. 1 Study flowchart\n\nPage 4 of 8Shoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \nTable 2 shows that the number of retrieved oocytes, \nMII (metaphase II) oocyte number, and the number \nof available blastocysts for transfer on day 5 were sig -\nnificantly higher in the group of frozen embryo transfer \n(p < 0.001).\nAs shown in Table  3, the number of embryos trans -\nferred was either a single embryo or two embryos, and \nthere was no statistical significant difference between \nthe two groups (p 0.473); for the quality of the embryos \ntransferred that were either high-quality embryos alone \nor low -quality embryos alone or both of them together, \nboth groups showed no statistically significant difference \n(p 0.325).\nThe clinical pregnancy rate was significantly higher in \nthe frozen embryo transfer group than the fresh group \n(82 patients (75.9%) vs 46 patients (44.7%) (p  < 0.001)); \nagain, the FET group showed a significantly higher \nTable 1 Comparison between the two studied groups according to the baseline characteristics\nBaseline characteristics Fresh ET (n = 103) Frozen ET (n = 108) Test of sig P\nMean age (years) 31.22 ± 4.94 30.87 ± 4.45 t = 0.546 0.586\nMedian infertility duration (IQR) \nyears\n4.0 (3.0–7.0) 4.25 (3.0–8.0) U = 5266.50 0.502\nMean BMI (kg/m2) 25.83 ± 3.26 25.01 ± 3.04 t = 1.903 0.058\nInfertility type No % No % χ2 = 3.987 0.136\n Primary 76 73.8 71 65.7\n Secondary 17 16.5 16 14.8\n Relative 10 9.7 21 19.4\nMean AMH 1.91 ± 1.11 2.21 ± 1.31 t = 1.813 0.071\nAFC U = 5064.5 0.258\n Mean 7.74 ± 2.93 8.18 ± 2.96\n Median (IQR) 7.0 (6.0–10.0) 8.0 (6.0–10.0)\nChocolate cyst before OI χ2 = 0.021 0.884\n Absent 87 (84.5%) 92 (85.2%)\n Present 16 (15.5%) 16 (14.8%)\nTable 2 Comparison between the two groups regarding the \nnumber of oocyte retrieved, mature oocytes, and available \nembryos number at day 5\n* : statistically significant \nFresh (n = 103) Frozen (n = 108) U p\nOocyte retrieved\n Min.–max 2.0–10.0 3.0–12.0 3710.5*  < 0.001*\n Mean ± SD 5.29 ± 2.08 6.56 ± 1.93\n Median (IQR) 5.0 (4.0–7.0) 6.0 (6.0–8.0)\nMII oocytes\n Min.–max 1.0–7.0 2.0–9.0 3546.5*  < 0.001*\n Mean ± SD 3.78 ± 1.62 4.87 ± 1.46\n Median (IQR) 4.0 (2.0–5.0) 5.0 (4.0–6.0)\nEmbryo no. on day 5\n Min.–max 1.0–5.0 1.0–7.0 3612.0*  < 0.001*\n Mean ± SD 2.55 ± 0.96 3.22 ± 1.06\n Median (IQR) 2.0 (2.0–3.0) 3.0 (2.0–4.0)\nTable 3 Comparison between the two studied groups according to the embryos transferred\nEmbryos transferred Fresh ET (n = 103) Frozen ET (n = 108) χ2 P\nNo % No %\nNumber\n Single embryo 47 45.6 44 40.7 0.514 0.473\n Two embryos 56 54.4 64 59.3\nQuality\n Low 26 25.2 22 20.4 2.246 0.325\n High 73 70.9 77 71.3\n High + low 4 3.9 9 8.3\n\nPage 5 of 8\nShoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \n \nimplantation rate in comparison to the fresh group as \nillustrated in Table 4  (30.8% vs 54.1% (p  < 0.001)).\nOut of the 128 pregnant females in the study, 3 preg -\nnant patients dropped out from the fresh group, and 6 \npregnant patients dropped out from the frozen group; \nthose 9 patients were excluded from our statistical \nresults while estimating the miscarriage rate. The mis -\ncarriage rate was higher in the fresh ET group than \nin the frozen ET group; however, the difference did \nnot reach statistical significance (9 (20.9%) vs 7 (9.2%) \n(p = 0.072).\nAs for the primary outcome of the study, the ongo -\ning pregnancy rate, out of the 211 patients included \nin our study, there was no available data for 9 pregnant \npatients, 3 patients in group 1, and 6 patients in group \n2; those 9 patients were excluded from our statistical \nanalysis while estimating the ongoing pregnancy rate. \nSixty-nine patients in the frozen embryo transfer group \n(69/102 = 67.6%) continued their pregnancy beyond \n14 weeks, while 33 patients (34/100 = 34%) of the fresh \nembryo transfer group continued their pregnancy \nbeyond 14 weeks, and the OPR was significantly higher \nin the frozen embryo transfer group (p < 0.001) (Table 5).\nFurthermore, a subgroup analysis was performed \nto compare the pregnancy rates between women who \nunderwent single embryo transfer (SET) and those to \nwhom two embryos were transferred (Table  6). It was \nobserved that the clinical and ongoing pregnancy rates \nin women who underwent SET and who have under -\nwent double embryo transfer are not significantly dif -\nferent (in the group of fresh ET, the group of FET, and \nfor the total sample).\nDiscussion\nThe present study showed that OPR in women with \nadvanced endometriosis is significantly higher in the \ngroup of frozen embryo transfer compared to the fresh \nembryo transfer group (67.6% vs. 34%, respectively). \nRegarding the secondary outcomes, there was a statisti -\ncally significant higher implantation and clinical preg -\nnancy rates also in the frozen embryo transfer group. \nTo the best of our knowledge, only few studies have \naddressed the issue of freeze-all policy in women with \nadvanced endometriosis.\nIn agreement with the findings of the current study, \nWu et  al. [18] conducted a retrospective study that \nTable 4 Comparison between the two studied groups according clinical pregnancy and implantation rates\n* : statistically significant \nFresh ET (n = 103) Frozen ET (n = 108) χ2 p\nNo % No %\nClinical pregnancy rate 46 44.7 82 75.9 21.597*  < 0.001*\nNumber of GS seen by TVU (after 3–5 weeks) 49 93  < 0.001*\nNumber of transferred embryos 159 172\nImplantation rate 30.8% 54.1%\nTable 5 Comparison between the two studied groups \naccording to the ongoing pregnancy\n* : statistically significant\nFresh ET Frozen ET χ2 p\nNo. (%) No. (%)\nOngoing pregnancy (n = 100) (n = 102) 22.876*  < 0.001*\n34 (34.0%) 69 (67.6%)\nTable 6 Relation between numbers of embryos transferred with \nclinical and ongoing pregnancy rates\na Not available cases were excluded\nNumber χ2 p\n1 2\nClinical pregnancy rate\n Fresh (n = 103) (n = 47) (n = 56)\n  Negative 30 (63.8%) 27 (48.2%) 2.521 0.112\n  Positive 17 (36.2%) 29 (51.8%)\n Frozen (n = 108) (n = 44) (n = 64)\n  Negative 9 (20.5%) 17 (26.6%) 0.532 0.466\n  Positive 35 (79.5%) 47 (73.4%)\n Total (n = 211) (n = 91) (n = 120)\n  Negative 39 (42.9%) 44 (36.7%) 0.831 0.362\n  Positive 52 (57.1%) 76 (63.3%)\nOngoing pregnancy rate\n Fresh (n = 100)a (n = 47) (n = 53)\n  Negative/miscarriage 35 (74.5%) 31 (58.5%) 2.834 0.092\n  Positive 12 (25.5%) 22 (41.5%)\n Frozen (n = 102)a (n = 43) (n = 59)\n  Negative/miscarriage 14 (32.6%) 19 (32.2%) 0.001 0.970\n  Positive 29 (67.4%) 40 (67.8%)\n Total (n = 202)a (n = 90) (n = 112)\n  Negative/miscarriage 49 (54.4%) 50 (44.6%) 1.918 0.166\n  Positive 41 (45.6%) 62 (55.4%)\n\nPage 6 of 8Shoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \nencompassed 1651 women with advanced stages of endo-\nmetriosis performing ICSI. After matching, 506 women \nand 255 women were eligible in the freeze-all group and \nthe fresh group, respectively. In their matched cohort \nstudy, the implantation, CPR, and LBR were significantly \nhigher in the FET group in comparison to the fresh \ngroups. Those results coincide with the current study in \nall perspectives except for the LBR as it was not included \nin the outcomes for the study.\nHowever, the present study differs from Wu et  al., \nwhere in their study the development of the embryo was \naccessed on day 3, and the embryos selected to be trans -\nferred were high-quality cleavage-stage embryos only (at \nleast six blastomeres with ≤ 20% fragmentation based \non the Cummins’ criteria). In the fresh embryo transfer \ngroup, patients were arranged for a day 3 fresh embryo \ntransfer and vitrification of the extra embryos. For the \nFET  group,  vitrification on day 3 of the entire cohort \nof good quality embryos. While in the present study, \nembryo development was assessed on day 5, and patients \nperforming fresh transfer were scheduled for a day-5 \nET, while in the frozen group, the embryos were vitri -\nfied on day 5, and embryo transfer was not exclusively \nfor high-quality embryos, but in some cases, average or \nlow-quality embryos were transferred either alone or in \ncombination with a high-quality embryo.\nAgain, the results of the present study coincided with \na matched cohort prospective study conducted by Bour -\ndon et al. [19], and they compared the results of FET to \nfresh ET in women having endometriosis, where the FET \ngroup involved 135 women and the fresh group involved \n424 matched women. CPR was of higher significance \ntoward the FET group in comparison to the fresh group; \nalso, the ongoing pregnancy rate showed greater statisti -\ncal significance in the FET group (34.8%) in comparison \nto the fresh-ET group (17.8%) (p = 0.005), and the live \nbirth rate as well was of higher significance in FET in \ncomparison to fresh embryo transfer group.\nAnother interesting study conducted by Mohamed \net  al. [20] is a retrospective, database-searched cohort \nstudy. The study included two groups: the first group had \nfreshly transferred embryos, while the second group per -\nformed frozen embryo transfer. The primary outcome for \nthe study was the live birth rate, while the secondary out-\ncomes included the clinical pregnancy rate and the mis -\ncarriage rate. Out of the total number of cases, 415 (5.7%) \nhad infertility attributed to endometriosis, in whom fro -\nzen ET cycles were associated with a relatively similar \nclinical pregnancy rate and live birth rate, in comparison \nto the clinical pregnancy rate and live birth rate of fresh \nET cycles, showing no significant difference. Neverthe -\nless, the study of Mohamed et al. differs from the present \nstudy as they considered other causes of infertility rather \nthan endometriosis alone as a sole factor of infertility, \nand it also concluded that there was no significant differ -\nence between FET over the fresh ET in cases of endome -\ntriosis concerning CPR (18.2 vs. 20.2%, respectively) and \nLBR (16.9% vs. 15.5%, respectively).\nIn accordance, a recent systematic review and meta-\nanalysis conducted by Chang et al. [21] aimed at evaluat -\ning if FET has the ability to reimpose optimal receptivity \ntargeting better ART results in patients with endometrio-\nsis. A total of six studies with moderate methodological \nquality were included in the meta-analysis. Three-thou -\nsand and ten patients with endometriosis who under -\nwent ICSI were included in the studies: 1777 performed \nFET, and 1233 performed fresh ET. LBR was significantly \nhigher in the FET group in comparison to the fresh \ngroup. Although that CPR was similar between the two \nstudy groups, there was a significantly higher miscarriage \nrate in the fresh group.\nThe endometrium of endometriosis-affected women \nis different from that of healthy, unaffected women [8], \nwhich could be the main reason for the decline in endo -\nmetrial receptivity quality. Thus, it is crucial to select the \nright embryo transfer technique, particularly for women \nwho have severe endometriosis. The effects of ovarian \nstimulation in fresh ET cycles on the early peri-implan -\ntation uterine milieu have been documented in a number \nof studies, and three-dimensional power Doppler ultra -\nsonography measurements have revealed that stimulated \ncycles have reduced endometrial and subendometrial \nblood flow in comparison to normal cycles [9]. Further -\nmore, certain pathologic alterations of the stimulated \nendometrium have been verified, such as the progression \nof endometrial maturation [10], as well as the early estab-\nlishment of nucleolar channel systems [11].\nAdditionally, a number of researchers have demon -\nstrated that during fresh embryo transfer cycles, there \nare abnormalities in the transcriptional activity of genes \nrelated to endometrial receptivity [22–24]. The altera -\ntions indicated above are linked to the hyperestrogenic \nenvironment created during fresh IVF, which might sub -\nsequently hinder early embryonic adhesion [18, 25] and, \nconsequently, the embryos’ capacity to implant. It follows \nthat the current study’s findings regarding implantation, \nclinical pregnancy, and ongoing pregnancy are better in \nFET cycles.\nOur study has the advantage of being one of the few \nstudies that addressed the role of FET in endometriosis-\naffected women and was conducted for a fair number \nof patients; moreover, this study focused on advanced \nendometriosis being the sole factor of infertility in the \nstudied patients, excluding any other infertility-related \nfactors; however, the main study limitation was being a \nretrospective analysis depending on the availability of \n\nPage 7 of 8\nShoukry et al. Middle East Fertility Society Journal           (2024) 29:41 \n \ncomplete medical records, and the follow-up stopped at \n14 weeks of gestation.\nConclusions\nThe findings of the present study suggest that frozen \nembryo transfer policy in cases of advanced endometrio -\nsis would result in better reproductive outcomes in com -\nparison to fresh embryo transfer in terms of clinical and \nongoing pregnancy rates. Further, randomized controlled \nstudies are needed for confirmation of such findings.\nAbbreviations\nART   Assisted reproductive technologies\nLBR  Live birth rate\nFET  Frozen embryo transfer\nASRM  American Society of Reproductive Medicine\nCPR  Clinical pregnancy rate\nOPR  Ongoing pregnancy rate\nIVF  In vitro fertilization\nICSI  Intracytoplasmic sperm injection\nGnRH  Gonadotropin-releasing hormone\nAMH  Anti-Mullerian hormone\nAcknowledgements\nNot applicable.\nAuthors’ contributions\nHA and AS were the main authors responsible of the research and writing the \npaper. MK was responsible for the data collection, and WEG was responsible \nfor reviewing and revising the paper. All authors read and approved the final \nmanuscript.\nFunding\nThe authors received no external funds.\nAvailability of data and materials\nThe datasets used and/or analyzed during the current study are available from \nthe corresponding author on reasonable request.\nDeclarations\nEthical approval and consent to participate\nThe study protocol was approved by the ethical committee of the Faculty of \nMedicine, Alexandria University, Egypt. No informed consent was required due \nto the retrospective design of the study.\nConsent for publication\nNot applicable.\nCompeting interests\nThe authors declare that they have no competing interests.\nReceived: 27 April 2024   Accepted: 4 August 2024\nReferences\n 1. Zegers-Hochschild F, Adamson GD, Dyer S, Racowsky C, De Mouzon J, \nSokol R, Cooke ID (2017) The international glossary on infertility and fertil-\nity care, 2017. Hum Reprod 32(9):1786–1801\n 2. 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