Hyperbilirubinemia and Retinopathy of Prematurity: A Retrospective Cohort Study

Hyperbilirubinemia and Retinopathy of Prematurity: A Retrospective Cohort Study | 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 Hyperbilirubinemia and Retinopathy of Prematurity: A Retrospective Cohort Study Silvia Gulden, Gaia Cervellini, Marta Colombo, Maria Beatrice Marangoni, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4241277/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 15 Jun, 2024 Read the published version in European Journal of Pediatrics → Version 1 posted 8 You are reading this latest preprint version Abstract Purpose. Retinopathy of prematurity (ROP) is a vasoproliferative retinal disease in preterm infants. Oxidative stress plays a key role in the pathogenesis of ROP. Bilirubin has been proposed to be protective against ROP due to its antioxidant effects. This study explored the association between hyperbilirubinemia and ROP. Methods. We analyzed a 10-year cohort from a neonatal intensive care unit in Milan, Italy, including 1606 infants born under 32 weeks and/or < 1500 g. Results. Data from 1606 infants meeting specific inclusion criteria were reviewed. Eighty infants were excluded due to lack of data, 1526 were deemed eligible for analysis, and 1269 had hyperbilirubinemia requiring phototherapy. There was a higher incidence of ROP among infants with hyperbilirubinemia (13.8%) versus those without (7.8%, p < 0.01). Infants with any ROP, non-severe or severe ROP, were exposed to hyperbilirubinemia for a significantly higher number of days compared with those without ROP. Each additional day of exposure increases the risk of developing any ROP by 5%, non-severe ROP by 4%, and severe ROP by 6%. However, this correlation was not observed in infants with gestational age less than 27 weeks and/or body weight less than 1000 g. Conclusion. Our data show that hyperbilirubinemia requiring phototherapy is associated with an increased risk of developing ROP. However, severe hyperbilirubinemia and ROP share many of their risk factors. Therefore, rather than being a risk factor itself, hyperbilirubinemia may be a surrogate for other risk factors for ROP. Clinical Trial Registration : NCT05806684 Newborn jaundice hyperbilirubinemia retinopathy of prematurity phototherapy Figures Figure 1 Figure 2 Figure 3 What is known The development of retinopathy of prematurity (ROP) is influenced by several critical risk factors, including low gestational age, low birth weight, supplemental oxygen use, and heightened oxidative stress. In vitro, unconjugated bilirubin is an effective scavenger of harmful oxygen species and a reducing agent, highlighting its potential protective role against oxidative stress. What is New: Hyperbilirubinemia requiring phototherapy increases ROP risk, yet there is no relation with extremely preterm infants, most at risk for severe ROP. Every additional day of phototherapy for hyperbilirubinemia increases the risk of ROP by 5% for any ROP, 4% for non-severe ROP, and 6% for severe ROP. Introduction Retinopathy of prematurity (ROP) is a retinal vasoproliferative disease of preterm infants. The reported incidence of ROP varies among regions, depending on the health care and socioeconomic level. It is increasing significantly in developing countries due to the improved survival of most immature infants [1; 2]. In most cases, ROP spontaneously regresses without residual damage, but it can cause severe visual impairment or blindness [1; 2]. Many studies have focused on identifying risk factors for ROP to develop the best preventive, screening, and therapeutic strategies [ 3 – 7 ]. Among these factors, low gestational age (GA), low birth weight (BW), use of supplemental oxygen, and increased oxidative stress have been shown to play pivotal roles [1; 2; 8]. Oxidative stress is an imbalance between reactive oxygen species (ROS) production and the body’s antioxidant defense mechanisms [ 9 ]. It occurs when there is an excessive increase of ROS or when the antioxidant defense systems are compromised. Preterm infants are more susceptible to oxidative stress due to several factors related to their immature physiology and the environment in which they are exposed [9; 10]. At birth, newborns are exposed to a relatively high oxygen environment, which increases oxygen bioavailability and ROS production. Additional sources of ROS are inflammation, hyperoxia, hypoxia, ischemia, or free iron release, which may increase oxidative stress. The immature antioxidant systems and reduced ability to control ROS overproduction amplify the situation, resulting in cell damage [9; 10]. Oxidative stress plays a key role in the pathogenesis of most prematurity-related conditions, including ROP, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), periventricular leukomalacia (PVL), intraventricular hemorrhage (IVH), and necrotizing enterocolitis (NEC) [ 9 – 12 ]. Neonatal hyperbilirubinemia is a common condition caused by increased heme catabolism and physiologic immaturity of the liver in bilirubin conjugation [ 13 ]. Preterms have a greater risk of severe hyperbilirubinemia, which can lead to kernicterus. However, one possible physiologic role for bilirubin is as an antioxidant [ 13 – 17 ]. Unconjugated bilirubin can scavenge singlet oxygen with high efficiency, react with superoxide anion and peroxyl radicals, and act as a reducing substrate for peroxidases when exposed to hydrogen peroxide or organic hydroperoxides [ 13 – 17 ]. Bilirubin levels correlate with total antioxidant capacity in the blood of neonates [18; 19]. Therefore, some authors have suggested that bilirubin may protect against oxidative stress-related prematurity complications, such as ROP. However, there have been conflicting results in studies that have attempted to analyze the potential association between hyperbilirubinemia and ROP [ 20 – 29 ]. The aim of the present study was to retrospectively analyze the potential association between hyperbilirubinemia and ROP in a cohort of newborns with a GA of less than 32 weeks admitted to our neonatal intensive care unit (NICU) between 2010 and 2020. Materials and methods This retrospective observational study was conducted in the third level (NICU) at Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy. All procedures were performed in accordance with the Helsinki Declaration. The study was approved by the local Ethics Committee (Milan Area 2, Italy) with approval number 951_2022. Due to the study’s retrospective nature, our Institutional Review Board has waived the need for informed consent from the parents. We retrospectively collected data from all premature infants born under 32 weeks of GA and/or less than 1500 g of BW hospitalized in our NICU between January 2010 and December 2020. We excluded patients with incomplete data on hyperbilirubinemia or ROP status. Through the electronic patient charts NeoCare® (GPI S.p.A., Trento, Italy), we collected the following data on the prenatal, perinatal, and neonatal period: GA, BW, sex, delivery characteristics, antenatal steroid administration, maternal comorbidities, APGAR score, resuscitation, death, RDS, severe IVH (greater than grade II), BPD, NEC, hemodynamically significant patent ductus arteriosus (HsPDA), early-onset sepsis (EOS), late-onset sepsis (LOS), ventilatory management, oxygen supplementation, number of red blood cell (RBC) transfusion and exchange transfusions, presence and length of hyperbilirubinemia, use and length of phototherapy, and ROP. Chorioamnionitis was defined as maternal fever ≥ 38° C, maternal/fetal tachycardia (> 100/160 bpm), uterine tenderness, and purulent fluid from the cervical os [ 30 ]. Preeclampsia was identified by new gestational hypertension after 20 weeks gestation, with systolic pressure ≥ 140 mmHg or diastolic pressure ≥ 90 mmHg twice, 4 hours apart, or severe spikes (systolic ≥ 160 mmHg, diastolic ≥ 110 mmHg) [ 31 ]. Small for gestational age (SGA) was defined as a birth weight below the 10th percentile for GA and sex [ 32 ]. RDS was defined by the combination of clinical and radiographic findings [ 33 ]. IVH was diagnosed by brain ultrasound and classified according to Papile et al. [ 34 ]. BPD was defined and classified according to Jobe and Bancalari [ 35 ]. NEC was diagnosed by clinical and radiographic findings and categorized by Bell staging [36; 37]. HsPDA was defined by clinical and echocardiographic signs [ 38 – 41 ]. EOS and LOS were defined as the positivity of blood cultures with clinical and laboratory signs of infection, respectively, before and after 72 hours of life [ 42 – 45 ]. Hyperbilirubinemia was diagnosed when the total serum bilirubin (TSB) level was above the threshold for phototherapy treatment, according to the National Institute for Health and Care Excellence (NICE) nomograms [ 46 ]. All infants in the study underwent ROP screening, and ROP was classified according to ICROP. Non-severe ROP was defined as stages 1 and 2, while severe ROP was defined as stage 3 or higher [ 47 ]. Statistical analysis Demographic characteristics of all infants were presented with descriptive statistics. Mean (standard deviation [SD]) and median (interquartile range [IQR]) were used for normal and non-normal continuous variables, and the two groups were compared using an independent t-test and Mann-Whitney U test, respectively. Absolute frequency (percentage) and χ 2 test were used to summarize and compare categorical variables. Mann-Whitney U test was used to compare the distribution of days of hyperbilirubinemia in the no ROP and any ROP groups. Kruskal-Wallis test was used to compare the three ROP groups (no ROP, non-severe, and severe ROP) with post hoc pairwise multiple comparisons performed using Dunn’s test. The association between ROP and length of hyperbilirubinemia was studied using the Poisson regression model with a robust error variance. Crude and adjusted risk ratio (RR), 95% confidence intervals (CI), and p -values were shown. Considered adjustment confounding variables were GA, sex, and SGA. Additionally, data were analyzed for the overall study population, and sub-analyses were performed for the subgroup that only included GA < 27 weeks and BW < 1000 g. R statistical software version 4.2.0 was used for all analyses [ 48 ]. All p-values < 0.05 were considered statistically significant. Results Figure 1 shows the study’s flow diagram [ 49 ]. The medical records of 1606 infants meeting the inclusion criteria and born in the selected years were reviewed. Of these, 80 were excluded because 62 had no data on hyperbilirubinemia, and 18 did not have data on ROP status. The remaining 1526 eligible infants were included in the analysis. Table 1 summarizes the population’s demographic characteristics and the differences between infants with and without hyperbilirubinemia. Of the entire cohort of patients included in the analysis, 1269 (83.2%) presented hyperbilirubinemia requiring phototherapy, while the remaining 257 (16.8%) did not. Table 1 Demographic characteristics Demographic data Overall (n = 1526) Hyperbilirubinemia p -value No (n = 257) Yes (n = 1269) Gestational age, weeks - mean (SD) 29.9 (2.8) 30.7 (3.2) 29.7 (2.7) < 0.001 a Birthweight, grams - mean (SD) 1199.7 (372.4) 1253.1 (365.1) 1188.8 (373.1) 0.012 a Male - n (%) 776 (50.9) 116 (45.1) 660 (52.0) 0.052 b Small gestational age - n (%) 492 (32.3) 111 (43.5) 381 (30.1) < 0.001 b Antenatal steroids - n (%) 1118 (77.5) 169 (76.1) 949 (77.8) 0.647 b Preterm premature rupture of membranes - n (%) 366 (24.6) 45 (18.6) 321 (25.7) 0.023 b Preeclampsia - n (%) 266 (18.0) 45 (18.8) 221 (17.8) 0.806 b Chorioamnionitis - n (%) 100 (6.7) 21 (8.7) 79 (6.4) 0.233 b Outborn – n (%) 184 (12.1) 62 (24.1) 122 (9.6) < 0.001 b Cesarean Section - n (%) 1219 (80.1) 195 (75.9) 1024 (81.0) < 0.001 b Delayed cord clamping - n (%) 199 (14.3) 29 (13.3) 170 (14.5) 0.722 b Umbilical cord milking - n (%) 103 (7.4) 14 (6.4) 89 (7.6) 0.634 b Apgar 1st minute - median [IQR] 7.0 [5.0, 8.0] 7.0 [5.0, 8.0] 6.0 [5.0, 8.0] 0.055 c Apgar 5th minutes - median [IQR] 8.0 [8.0, 9.0] 8.0 [7.0, 9.0] 8.0 [8.0, 9.0] 0,619 c Apgar 10th minutes - median [IQR] 8.0 [7.0, 9.0] 8.0 [6.0, 8.0] 8.0 [8.0, 9.0] 0.010 c Venous cord blood pH - mean (SD) 7.3 (0.1) 7.3 (0.1) 7.3 (0.1) 0.304 a Arterial cord blood pH - mean (SD) 7.2 (0.1) 7.2 (0.1) 7.2 (0.1) 0.983 a Mechanical ventilation - n (%) 678 (44.7) 112 (43.9) 566 (44.9) 0.831 b Days of mechanical ventilation - median [IQR] 0.0 [0.0, 5.0] 0.0 [0.0, 4.0] 0.0 [0.0, 5.0] 0.737 c Non-invasive ventilation - n (%) 1243 (82.0) 176 (69.0) 1067 (84.6) < 0.001 b Days of non-invasive ventilation - median [IQR] 10.0 [2.0, 35.0] 5.0 [0.0, 21.0] 11.0 [3.0, 37.0] < 0.001 c Days of O 2 therapy - median [IQR] 3.0 [0.0, 17.0] 2.0 [0.0, 10.5] 3.0 [0.0, 19.7] 0.003 c Red blood cell transfusions - median [IQR] 0.0 [0.0, 2.0] 0.0 [0.0, 1.0] 0.0 [0.0, 3.0] 0.018 c Exchange transfusions - n (%) 56 (3.7) 5 (1.9) 51 (4.0) 0.149 b Days of hyperbilirubinemia - median [IQR] 2.0 [1.0, 4.0] 0.0 [0.0, 0.0] 3.0 [2.0, 4.0] < 0.001 c Phototherapy - n (%) 1253 (82.6) 1 (0.4) 1252 (99.4) < 0.001 b Days of phototherapy - median [IQR] 2.0 [1.0, 4.0] 0.0 [0.0, 0.0] 3.0 [2.0, 4.0] < 0.001 Respiratory distress syndrome - n (%) 1042 (69.1) 145 (57.3) 897 (71.4) < 0.001 b Severe intraventricular hemorrhage - n (%) 82 (5.5) 12 (4.8) 70 (5.6) 0.726 b Bronchopulmonary disease - n (%) 73 (11.5) 9 (7.3) 64 (12.5) 0.142 b Necrotizing enterocolitis - n (%) 155 (10.3) 32 (12.6) 123 (9.9) 0.227 b Hemodynamically patent ductus arteriosus - n (%) 438 (29.1) 75 (29.8) 363 (29.0) 0.866 b Early-onset sepsis - n (%) 53 (3.5) 11 (4.3) 42 (3.4) 0.563 b Late-onset sepsis - n (%) 352 (23.5) 55 (21.7) 297 (23.9) 0.516 b Death - n (%) 139 (9.1) 30 (11.7) 109 (8.6) 0.149 b IQR: interquartile range; n: number; SD: standard deviation; a t-test, b χ 2 test, c Mann-Whitney U test. The mean (SD) GA of the overall population was 29.9 (2.8) weeks, and the mean BW was 1199.7 (372.5) grams. Infants with hyperbilirubinemia had an average of 1-week lower GA and 60 grams less BW than patients without hyperbilirubinemia (p < 0.001 and p = 0.012, respectively). There was no difference in sex between infants with and without hyperbilirubinemia. However, the non-hyperbilirubinemia group had more infants who were SGA or outborn. Infants born to mothers who had preterm premature rupture of membranes or cesarean deliveries had higher rates of hyperbilirubinemia. APGAR scores were similar in both groups at the 1st and 5th minutes, but the hyperbilirubinemia group had slightly higher IQR at 10 minutes. More than 70% of neonates with hyperbilirubinemia developed RDS, resulting in increased use of non-invasive ventilation and prolonged oxygen therapy. Infants with hyperbilirubinemia received more RBC transfusions, although exchange transfusion rates were similar in both groups. The incidence of all other analyzed neonatal outcomes was similar in both groups. In the total population, 12.8% of the infants had ROP. The rate of any ROP was higher in the infants with hyperbilirubinemia (13.8%) when compared with the infants without hyperbilirubinemia (7.8%, p < 0.01). The rates of non-severe and severe ROP in the groups with and without hyperbilirubinemia were (8.0% vs. 3.9% and 5.8% vs. 3.9%). As shown in Fig. 2 , the median number of days of exposure to hyperbilirubinemia was significantly higher in infants with any ROP compared to infants without ROP (3 days [IQR: 2 to 5] vs. 2 days [IQR: 1 to 4], p < 0.001). Furthermore, the significant difference in days of exposure to hyperbilirubinemia was maintained when the non-ROP group was compared to both the non-severe ROP and severe ROP groups (Fig. 3 ). The results of the Poisson regression model, adjusted for GA, sex, and SGA, showed that infants exposed to hyperbilirubinemia had a higher risk of developing any grade of ROP. Each additional day of hyperbilirubinemia increased the risk of developing any ROP by 5%, non-severe ROP by 4%, and severe ROP by 6% compared to the group without ROP (Table 2 ). Finally, in the analysis conducted on the sub-population with GA less than 27 weeks and/or BW less than 1000 g, it was observed that the days of hyperbilirubinemia were not associated with ROP in either the crude or adjusted models (Table 3 ). Table 2 Poisson regression models’ results between days of hyperbilirubinemia and ROP for the overall population Crude Adjusted * RR 95% CI p -value RR 95% CI p -value No ROP vs. Any ROP 1.07 0.997; 1.154 0.060 1,05 1.008; 1.084 0,016 No ROP vs. Non-Severe ROP 1.05 0.986; 1.111 0.137 1,04 1.001; 1.073 0,043 No ROP vs. Severe ROP 1.06 0.987; 1.147 0.103 1,06 1.023; 1.099 0,001 Non-Severe ROP vs. Severe ROP 1.03 0.980; 1.079 0.263 1,01 0.969; 1.056 0,600 ROP: Retinopathy of Prematurity; RR: risk ratio; CI: confidence interval; *adjusted for gestational age, sex, and small for gestational age Table 3 Poisson regression models’ results between days of hyperbilirubinemia and ROP for patients with GA < 27 weeks and BW < 1000 g GA < 27 weeks and BW < 1000 g Crude Adjusted* RR 95% CI p -value RR 95% CI p -value No ROP vs. Any ROP 1.13 0.978; 1.314 0.095 1,11 0.97; 1.277 0,128 No ROP vs. Non-Severe ROP 1.10 0.972; 1.241 0.132 1,09 0.978; 1.208 0,123 No ROP vs. Severe ROP 1.12 0.975; 1.287 0.110 1,11 0.971; 1.274 0,125 Non-Severe ROP vs. Severe ROP 1.02 0.966; 1.073 0.498 1,02 0.95; 1.093 0,600 BW: birth weight; CI: confidence interval; GA: gestational age; ROP: Retinopathy of Prematurity; RR: risk ratio; *adjusted for gestational age, sex, and small for gestational age Discussion The potential role of bilirubin in the pathogenesis of ROP is controversial. It has been suggested that bilirubin is protective against ROP due to its antioxidant effects [50; 51], but also that hyperbilirubinemia is a risk factor for the development of ROP [20–29; 52–54]. The results of our retrospective analysis in a cohort of 1526 very preterm infants are consistent with the second suggestion. Our study shows that hyperbilirubinemia requiring phototherapy is associated with an increased risk of developing ROP. However, the association between hyperbilirubinemia and ROP could not be observed in the subgroup with the lowest GA, which is more susceptible to developing severe ROP. The main limitations of our study are its retrospective nature and the lack of information on the actual bilirubin levels of the infants. Since our criterion for the definition of hyperbilirubinemia was the need for phototherapy, we cannot exclude a possible protective effect of moderate bilirubin levels against ROP in the group that did not require phototherapy. Currently, there is limited knowledge about what serum bilirubin levels are beneficial or detrimental, and studies have yielded conflicting results. Shahab et al. reported that TSB levels up to 20 mg/dl may protect term neonates from oxidative stress-related pathologies. However, the protective effect decreases above 20 mg/dl [ 55 ]. Other studies suggest that TSB levels above 5.1 mg/dl may reduce the risk of severe ROP in neonates undergoing phototherapy [56; 57]. In contrast, by associating higher peak TSB levels with an increased risk of severe ROP, Milner et al. contradicted the protective role of bilirubin [ 58 ]. It should also be noted that some investigators have questioned the antioxidant effects of neonatal bilirubin, demonstrating a negative correlation between serum bilirubin levels and antioxidant capacity [59; 60]. Dani et al. speculated that this is the result of the pro-oxidant effect of heme oxygenase mediated by iron release, which counteracts the antioxidant properties of bilirubin [ 59 ]. Another limitation of our phototherapy-based definition of hyperbilirubinemia is its inability to separate the ocular effects of phototherapy from the ocular effects of hyperbilirubinemia. Of note, the wavelengths of light that are most efficient in decreasing bilirubin levels are also the wavelengths likely to produce retinal damage [ 61 ]. Moreover, it has been suggested that some of the harmful effects of phototherapy on ROP may be related to its ability to reduce the antioxidant capacity of bilirubin [ 61 ]. Therefore, by degrading bilirubin, phototherapy may decrease the capacity of oxidation resistance and may increase ROS in both the retina and serum [21; 62; 63]. The association between length of phototherapy and risk of ROP was previously shown in a small study by Khatami et al. and has now been confirmed in a much larger cohort [ 64 ]. It is noteworthy that this association between the duration of phototherapy and the risk of developing ROP was not observed in the subgroup of infants with a GA of less than 27 weeks. This is the group that has the highest risk of developing ROP and is also the group that is most exposed to oxidative stress. Since ROP is a condition with multifactorial pathogenesis, we speculate that a factor such as hyperbilirubinemia may not make a difference in a population with a higher baseline risk of ROP. Accordingly, the association between hyperbilirubinemia and ROP has not been found in infants with higher GA [65; 66]. Finally, it should be noted that many of the risk factors for developing ROP are the same as those for developing severe hyperbilirubinemia [ 67 ]. Thus, hyperbilirubinemia may be a surrogate for other risk factors for ROP rather than a risk factor itself. In conclusion, this retrospective study showed an association between hyperbilirubinemia requiring phototherapy and the risk of developing ROP in very preterm infants. However, association does not imply causation. ROP is a multifactorial condition, and it is difficult to determine the pathogenic role of individual risk factors. Our data suggest that high bilirubin levels, i.e., those requiring phototherapy, do not protect the developing retina from oxidative stress. It remains to be determined whether lower bilirubin levels have this protective antioxidant effect against ROP and other oxidative stress-mediated conditions of the preterm infant. Declarations Author Contributions: S.G., G.R., M.B.M., G.A., M.F., F.G., S.O., E.V., and G.C. (Giacomo Cavallaro) contributed to the study’s conception and design; S.G., G.R., G.C. (Gaia Cervellini), M.C., V.T., F.G., E.V., and G.C. (Giacomo Cavallaro) contributed to the study’s methodology, investigation, and data curation; S.G., G.C. (Gaia Cervellini), M.C., V.T., M.B.M., and S.O. contributed to data collection; N.P. performed the statistical analysis; S.G., G.C. (Gaia Cervellini), G.R., M.B.M., and G.C. (Giacomo Cavallaro) wrote the initial draft preparation of the manuscript; S.G., G.R., G.C. (Gaia Cervellini), M.B.M., G.A., F.G., E.V., and G.C. (Giacomo Cavallaro) wrote, reviewed, and edited the manuscript; The co-first S.G. and G.C. (Gaia Cervellini), and co-last E.V. and G.C. (Giacomo Cavallaro) authorship contributed equally and have the right to list their name as first or last in their Curriculum Vitae. E.V. and G.C. (Giacomo Cavallaro) contributed equally to the visualization of the manuscript; G.C. (Giacomo Cavallaro) contributed to the supervision and project administration of the study. All authors have read and agreed to the published version of the manuscript. 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Curr Opin Pediatr 32:235-244 Shepherd JL, Noori S (2019) What is a hemodynamically significant PDA in preterm infants? Congenit Heart Dis 14:21-26 Shane AL, Sánchez PJ, Stoll BJ (2017) Neonatal sepsis. Lancet 390:1770-1780 Procianoy RS, Silveira RC (2020) The challenges of neonatal sepsis management. J Pediatr (Rio J) 96:80-86 Hornik CP, Fort P, Clark RH, Watt K, Benjamin Jr DK, Smith PB, Manzoni P, Jacqz-Aigrain E, Kaguelidou F, Cohen-Wolkowiez M (2012) Early and late onset sepsis in very-low-birth-weight infants from a large group of neonatal intensive care units. Early Hum Dev 88:S69-S74 Cohen-Wolkowiez M, Moran C, Benjamin DK, Cotten CM, Clark RH, Benjamin Jr DK, Smith PB (2009) Early and late onset sepsis in late preterm infants. The Pediatric infectious disease journal 28:1052-1056 Amos RC, Jacob H, Leith W (2017) Jaundice in newborn babies under 28 days: NICE guideline 2016 (CG98). Archives of Disease in Childhood-Education and Practice 102:207-209 Prematurity. ICftCoRo (2005) The International Classification of Retinopathy of Prematurity revisited. Arch Ophthalmol 123:991-999. doi: 10.1001/archopht.123.7.991: R-Core-Team (2013) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, Shamseer L, Tetzlaff JM, Akl EA, Brennan SE (2021) The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. International journal of surgery 88:105906 Hammermann C, Goldstein R, Kaplan M, Eran M, Goldschmidt D, Eidelman AI (1998) Bilirubin in the premature: toxic waste or natural defense? Clin Chem 44:2551-2553 Hegyi T, Goldie E, Hiatt M (1994) The protective role of bilirubin in oxygen-radical diseases of the preterm infant. J Perinatol 14:296-300 Akkawi MT, Shehadeh MM, Shams ANA, Al-Hardan DM, Omar LJ, Almahmoud OH, Qaddumi JAS (2019) Incidence and risk factors of retinopathy of prematurity in three neonatal intensive care units in Palestine. BMC Ophthalmol 19:189. doi: 10.1186/s12886-019-1180-4: Gopinathan V, Miller NJ, Milner AD, Rice-Evans CA (1994) Bilirubin and ascorbate antioxidant activity in neonatal plasma. FEBS Lett 349:197-200. doi: 10.1016/0014-5793(94)00666-0: Hosono S, Ohno T, Kimoto H, Shimizu M, Nozawa M, Genkawa R, Yoshida T, Wada S, Harada K (2002) No clinical correlation between bilirubin levels and severity of retinopathy of prematurity. J Pediatr Ophthalmol Strabismus 39:151-156 Shekeeb Shahab M, Kumar P, Sharma N, Narang A, Prasad R (2008) Evaluation of oxidant and antioxidant status in term neonates: a plausible protective role of bilirubin. Mol Cell Biochem 317:51-59. doi: 10.1007/s11010-008-9807-4: Mohagheghi P, Poorsattar A, Jalali A (2008) Bilirubin may protect from severe ROP. Early Hum Dev:S47 Fereshtehnejad SM, Mir KPB, Mir APB, Mohagheghi P (2012) Evaluation of the possible antioxidative role of bilirubin protecting from free radical related illnesses in neonates. Acta Medica Iranica:153-163 Milner JD, Aly HZ, Ward LB, El-Mohandes A (2003) Does elevated peak bilirubin protect from retinopathy of prematurity in very low birthweight infants. J Perinatol 23:208-211 Dani C, Martelli E, Bertini G, Pezzati M, Filippi L, Rossetti M, Rizzuti G, Rubaltelli FF (2003) Plasma bilirubin level and oxidative stress in preterm infants. Arch Dis Child Fetal Neonatal Ed 88:F119-123. doi: 10.1136/fn.88.2.f119: Yiğit S, Yurdakök M, Kilin K, Oran O, Erdem G, Tekinalp G (1999) Serum malondialdehyde concentration in babies with hyperbilirubinaemia. Arch Dis Child Fetal Neonatal Ed 80:F235-237. doi: 10.1136/fn.80.3.f235: Xiong T, Qu Y, Cambier S, Mu D (2011) The side effects of phototherapy for neonatal jaundice: what do we know? What should we do? Eur J Pediatr 170:1247-1255 Boskabadi H, Kalate M (2018) Effect of phototherapy on pro-oxidant/antioxidant balance in newborns with Jaundice. BIOMEDICAL RESEARCH AND THERAPY 5:2432-2439 Aycicek A, Erel O (2007) Total oxidant/antioxidant status in jaundiced newborns before and after phototherapy. J Pediatr (Rio J) 83:319-322 Khatami SF, Yousefi A, Bayat GF, Mamuri G (2008) Retinopathy of prematurity among 1000-2000 gram birth weight newborn infants. Iranian journal of pediatrics 18:137-142 Abdel Hadi AM, Shereenhamdy (2013) Correlation between risk factors during the neonatal period and appearance of retinopathy of prematurity in preterm infants in neonatal intensive care units in Alexandria, Egypt. Clinical Ophthalmology:831. doi: 10.2147/opth.s40136: Gleissner M, Spantzel T, Bücker-Nott H, Jorch G (2003) Risk factors of retinopathy of prematurity in infants 32 to 36 weeks gestational age. Z Geburtshilfe Neonatol 207:24-28 Pillai A, Pandita A, Osiovich H, Manhas D (2020) Pathogenesis and management of indirect hyperbilirubinemia in preterm neonates less than 35 weeks: moving toward a standardized approach. Neoreviews 21:e298-e307 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 15 Jun, 2024 Read the published version in European Journal of Pediatrics → Version 1 posted Editorial decision: Revision requested 01 May, 2024 Reviews received at journal 19 Apr, 2024 Reviewers agreed at journal 13 Apr, 2024 Reviewers agreed at journal 12 Apr, 2024 Reviewers invited by journal 12 Apr, 2024 Editor assigned by journal 11 Apr, 2024 Submission checks completed at journal 11 Apr, 2024 First submitted to journal 09 Apr, 2024 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4241277","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":290783612,"identity":"558dc178-c7c9-4c0b-bac2-a7adccc4259a","order_by":0,"name":"Silvia Gulden","email":"","orcid":"","institution":"Neonatal Intensive Care Unit, Sant’Anna Hospital, Como","correspondingAuthor":false,"prefix":"","firstName":"Silvia","middleName":"","lastName":"Gulden","suffix":""},{"id":290783613,"identity":"3fc6a010-1199-4ffd-9b41-36b95028b898","order_by":1,"name":"Gaia Cervellini","email":"","orcid":"","institution":"Neonatal Intensive Care Unit, 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Garrido","email":"","orcid":"","institution":"Neonatal Intensive Care Unit, Clínica Universidad de Navarra, Madrid","correspondingAuthor":false,"prefix":"","firstName":"Felipe","middleName":"","lastName":"Garrido","suffix":""},{"id":290783623,"identity":"48d26314-0f15-4ebd-ab40-45ca7587ae76","order_by":11,"name":"Eduardo Villamor","email":"","orcid":"","institution":"MosaKids Children’s Hospital, Maastricht University Medical Center (MUMC+), School for Oncology and Reproduction (GROW), Maastricht University, Maastricht","correspondingAuthor":false,"prefix":"","firstName":"Eduardo","middleName":"","lastName":"Villamor","suffix":""},{"id":290783624,"identity":"6a3b5f73-127f-4fec-b091-151b9f95f056","order_by":12,"name":"Giacomo Cavallaro","email":"","orcid":"","institution":"Neonatal Intensive Care Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan","correspondingAuthor":false,"prefix":"","firstName":"Giacomo","middleName":"","lastName":"Cavallaro","suffix":""}],"badges":[],"createdAt":"2024-04-09 10:42:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4241277/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4241277/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00431-024-05630-3","type":"published","date":"2024-06-15T14:54:24+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54861765,"identity":"599ec60c-0884-4ce1-a10d-d910cea23700","added_by":"auto","created_at":"2024-04-17 19:59:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":129454,"visible":true,"origin":"","legend":"\u003cp\u003eThe PRISMA flow diagram of the study.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4241277/v1/e2e3606ccca6cd55912ef8c4.png"},{"id":54861764,"identity":"0ae59a84-6ebd-44ff-8d33-098be31a3897","added_by":"auto","created_at":"2024-04-17 19:59:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":227033,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between days of hyperbilirubinemia vs. no ROP and any ROP groups. ***\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4241277/v1/54771b34252f4122b619c0b2.png"},{"id":54861766,"identity":"a31e6d64-3caf-4d14-9058-8870cc31ac60","added_by":"auto","created_at":"2024-04-17 19:59:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":296075,"visible":true,"origin":"","legend":"\u003cp\u003eRelationship between days of hyperbilirubinemia vs. no ROP and non-severe or severe ROP. **\u003cem\u003ep=\u003c/em\u003e 0.004; ***\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.001\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-4241277/v1/39b25c365e976838d6743fb6.png"},{"id":58822322,"identity":"0ea4ee5a-4f41-4262-97e5-2460a4db987b","added_by":"auto","created_at":"2024-06-21 16:40:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1465460,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4241277/v1/b3bca929-6d91-4ac7-bea1-c5d10f63c8dc.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eHyperbilirubinemia and Retinopathy of Prematurity: A Retrospective Cohort Study\u003c/p\u003e","fulltext":[{"header":"What is known","content":"\u003col\u003e\n \u003cli\u003eThe development of retinopathy of prematurity (ROP) is influenced by several critical risk factors, including low gestational age, low birth weight, supplemental oxygen use, and heightened oxidative stress.\u003c/li\u003e\n \u003cli\u003eIn vitro, unconjugated bilirubin is an effective scavenger of harmful oxygen species and a reducing agent, highlighting its potential protective role against oxidative stress.\u0026nbsp;\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003eWhat is New:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eHyperbilirubinemia requiring phototherapy increases ROP risk, yet there is no relation with extremely preterm infants, most at risk for severe ROP.\u003c/li\u003e\n \u003cli\u003eEvery additional day of phototherapy for hyperbilirubinemia increases the risk of ROP by 5% for any ROP, 4% for non-severe ROP, and 6% for severe ROP.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Introduction","content":"\u003cp\u003eRetinopathy of prematurity (ROP) is a retinal vasoproliferative disease of preterm infants. The reported incidence of ROP varies among regions, depending on the health care and socioeconomic level. It is increasing significantly in developing countries due to the improved survival of most immature infants [1; 2]. In most cases, ROP spontaneously regresses without residual damage, but it can cause severe visual impairment or blindness [1; 2].\u003c/p\u003e \u003cp\u003eMany studies have focused on identifying risk factors for ROP to develop the best preventive, screening, and therapeutic strategies [\u003cspan additionalcitationids=\"CR4 CR5 CR6\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Among these factors, low gestational age (GA), low birth weight (BW), use of supplemental oxygen, and increased oxidative stress have been shown to play pivotal roles [1; 2; 8].\u003c/p\u003e \u003cp\u003eOxidative stress is an imbalance between reactive oxygen species (ROS) production and the body\u0026rsquo;s antioxidant defense mechanisms [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It occurs when there is an excessive increase of ROS or when the antioxidant defense systems are compromised. Preterm infants are more susceptible to oxidative stress due to several factors related to their immature physiology and the environment in which they are exposed [9; 10]. At birth, newborns are exposed to a relatively high oxygen environment, which increases oxygen bioavailability and ROS production. Additional sources of ROS are inflammation, hyperoxia, hypoxia, ischemia, or free iron release, which may increase oxidative stress. The immature antioxidant systems and reduced ability to control ROS overproduction amplify the situation, resulting in cell damage [9; 10].\u003c/p\u003e \u003cp\u003eOxidative stress plays a key role in the pathogenesis of most prematurity-related conditions, including ROP, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), periventricular leukomalacia (PVL), intraventricular hemorrhage (IVH), and necrotizing enterocolitis (NEC) [\u003cspan additionalcitationids=\"CR10 CR11\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eNeonatal hyperbilirubinemia is a common condition caused by increased heme catabolism and physiologic immaturity of the liver in bilirubin conjugation [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Preterms have a greater risk of severe hyperbilirubinemia, which can lead to kernicterus. However, one possible physiologic role for bilirubin is as an antioxidant [\u003cspan additionalcitationids=\"CR14 CR15 CR16\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Unconjugated bilirubin can scavenge singlet oxygen with high efficiency, react with superoxide anion and peroxyl radicals, and act as a reducing substrate for peroxidases when exposed to hydrogen peroxide or organic hydroperoxides [\u003cspan additionalcitationids=\"CR14 CR15 CR16\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBilirubin levels correlate with total antioxidant capacity in the blood of neonates [18; 19]. Therefore, some authors have suggested that bilirubin may protect against oxidative stress-related prematurity complications, such as ROP. However, there have been conflicting results in studies that have attempted to analyze the potential association between hyperbilirubinemia and ROP [\u003cspan additionalcitationids=\"CR21 CR22 CR23 CR24 CR25 CR26 CR27 CR28\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The aim of the present study was to retrospectively analyze the potential association between hyperbilirubinemia and ROP in a cohort of newborns with a GA of less than 32 weeks admitted to our neonatal intensive care unit (NICU) between 2010 and 2020.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eThis retrospective observational study was conducted in the third level (NICU) at Fondazione IRCCS Ca\u0026rsquo; Granda Ospedale Maggiore Policlinico, Milan, Italy.\u003c/p\u003e \u003cp\u003e All procedures were performed in accordance with the Helsinki Declaration. The study was approved by the local Ethics Committee (Milan Area 2, Italy) with approval number 951_2022. Due to the study\u0026rsquo;s retrospective nature, our Institutional Review Board has waived the need for informed consent from the parents.\u003c/p\u003e \u003cp\u003eWe retrospectively collected data from all premature infants born under 32 weeks of GA and/or less than 1500 g of BW hospitalized in our NICU between January 2010 and December 2020. We excluded patients with incomplete data on hyperbilirubinemia or ROP status.\u003c/p\u003e \u003cp\u003eThrough the electronic patient charts NeoCare\u0026reg; (GPI S.p.A., Trento, Italy), we collected the following data on the prenatal, perinatal, and neonatal period: GA, BW, sex, delivery characteristics, antenatal steroid administration, maternal comorbidities, APGAR score, resuscitation, death, RDS, severe IVH (greater than grade II), BPD, NEC, hemodynamically significant patent ductus arteriosus (HsPDA), early-onset sepsis (EOS), late-onset sepsis (LOS), ventilatory management, oxygen supplementation, number of red blood cell (RBC) transfusion and exchange transfusions, presence and length of hyperbilirubinemia, use and length of phototherapy, and ROP.\u003c/p\u003e \u003cp\u003eChorioamnionitis was defined as maternal fever\u0026thinsp;\u0026ge;\u0026thinsp;38\u0026deg; C, maternal/fetal tachycardia (\u0026gt;\u0026thinsp;100/160 bpm), uterine tenderness, and purulent fluid from the cervical os [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Preeclampsia was identified by new gestational hypertension after 20 weeks gestation, with systolic pressure\u0026thinsp;\u0026ge;\u0026thinsp;140 mmHg or diastolic pressure\u0026thinsp;\u0026ge;\u0026thinsp;90 mmHg twice, 4 hours apart, or severe spikes (systolic\u0026thinsp;\u0026ge;\u0026thinsp;160 mmHg, diastolic\u0026thinsp;\u0026ge;\u0026thinsp;110 mmHg) [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Small for gestational age (SGA) was defined as a birth weight below the 10th percentile for GA and sex [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. RDS was defined by the combination of clinical and radiographic findings [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. IVH was diagnosed by brain ultrasound and classified according to Papile et al. [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. BPD was defined and classified according to Jobe and Bancalari [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. NEC was diagnosed by clinical and radiographic findings and categorized by Bell staging [36; 37]. HsPDA was defined by clinical and echocardiographic signs [\u003cspan additionalcitationids=\"CR39 CR40\" citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. EOS and LOS were defined as the positivity of blood cultures with clinical and laboratory signs of infection, respectively, before and after 72 hours of life [\u003cspan additionalcitationids=\"CR43 CR44\" citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Hyperbilirubinemia was diagnosed when the total serum bilirubin (TSB) level was above the threshold for phototherapy treatment, according to the National Institute for Health and Care Excellence (NICE) nomograms [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. All infants in the study underwent ROP screening, and ROP was classified according to ICROP. Non-severe ROP was defined as stages 1 and 2, while severe ROP was defined as stage 3 or higher [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eDemographic characteristics of all infants were presented with descriptive statistics. Mean (standard deviation [SD]) and median (interquartile range [IQR]) were used for normal and non-normal continuous variables, and the two groups were compared using an independent t-test and Mann-Whitney U test, respectively. Absolute frequency (percentage) and χ\u003csup\u003e2\u003c/sup\u003e test were used to summarize and compare categorical variables. Mann-Whitney U test was used to compare the distribution of days of hyperbilirubinemia in the no ROP and any ROP groups. Kruskal-Wallis test was used to compare the three ROP groups (no ROP, non-severe, and severe ROP) with post hoc pairwise multiple comparisons performed using Dunn\u0026rsquo;s test. The association between ROP and length of hyperbilirubinemia was studied using the Poisson regression model with a robust error variance. Crude and adjusted risk ratio (RR), 95% confidence intervals (CI), and \u003cem\u003ep\u003c/em\u003e-values were shown. Considered adjustment confounding variables were GA, sex, and SGA.\u003c/p\u003e \u003cp\u003eAdditionally, data were analyzed for the overall study population, and sub-analyses were performed for the subgroup that only included GA\u0026thinsp;\u0026lt;\u0026thinsp;27 weeks and BW\u0026thinsp;\u0026lt;\u0026thinsp;1000 g. R statistical software version 4.2.0 was used for all analyses [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. All p-values\u0026thinsp;\u0026lt;\u0026thinsp;0.05 were considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows the study\u0026rsquo;s flow diagram [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. The medical records of 1606 infants meeting the inclusion criteria and born in the selected years were reviewed. Of these, 80 were excluded because 62 had no data on hyperbilirubinemia, and 18 did not have data on ROP status. The remaining 1526 eligible infants were included in the analysis.\u003c/p\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the population\u0026rsquo;s demographic characteristics and the differences between infants with and without hyperbilirubinemia. Of the entire cohort of patients included in the analysis, 1269 (83.2%) presented hyperbilirubinemia requiring phototherapy, while the remaining 257 (16.8%) did not.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDemographic data\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eOverall (n\u0026thinsp;=\u0026thinsp;1526)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eHyperbilirubinemia\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo (n\u0026thinsp;=\u0026thinsp;257)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes (n\u0026thinsp;=\u0026thinsp;1269)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGestational age, weeks - mean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e29.9 (2.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30.7 (3.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e29.7 (2.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBirthweight, grams - mean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1199.7 (372.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1253.1 (365.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1188.8 (373.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.012\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e776 (50.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e116 (45.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e660 (52.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.052\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSmall gestational age - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e492 (32.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e111 (43.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e381 (30.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAntenatal steroids - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1118 (77.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e169 (76.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e949 (77.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.647\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreterm premature rupture of membranes - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e366 (24.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45 (18.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e321 (25.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.023\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePreeclampsia - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e266 (18.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e45 (18.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e221 (17.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.806\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eChorioamnionitis - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100 (6.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21 (8.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e79 (6.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.233\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOutborn \u0026ndash; n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e184 (12.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e62 (24.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e122 (9.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCesarean Section - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1219 (80.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e195 (75.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1024 (81.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDelayed cord clamping - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e199 (14.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29 (13.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e170 (14.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.722\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUmbilical cord milking - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e103 (7.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 (6.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e89 (7.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.634\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApgar 1st minute - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.0 [5.0, 8.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.0 [5.0, 8.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.0 [5.0, 8.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.055\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApgar 5th minutes - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.0 [8.0, 9.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.0 [7.0, 9.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.0 [8.0, 9.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0,619\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApgar 10th minutes - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.0 [7.0, 9.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.0 [6.0, 8.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.0 [8.0, 9.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.010\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVenous cord blood pH - mean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.3 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.3 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.3 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.304\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eArterial cord blood pH - mean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.2 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.2 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.2 (0.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.983\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMechanical ventilation - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e678 (44.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e112 (43.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e566 (44.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.831\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays of mechanical ventilation - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0 [0.0, 5.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0 [0.0, 4.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0 [0.0, 5.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.737\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-invasive ventilation - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1243 (82.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e176 (69.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1067 (84.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays of non-invasive ventilation - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.0 [2.0, 35.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.0 [0.0, 21.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11.0 [3.0, 37.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays of O\u003csub\u003e2\u003c/sub\u003e therapy - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.0 [0.0, 17.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.0 [0.0, 10.5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0 [0.0, 19.7]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.003\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRed blood cell transfusions - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.0 [0.0, 2.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0 [0.0, 1.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0 [0.0, 3.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.018\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExchange transfusions - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e56 (3.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (1.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e51 (4.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.149\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays of hyperbilirubinemia - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0 [1.0, 4.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0 [0.0, 0.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0 [2.0, 4.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePhototherapy - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1253 (82.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (0.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1252 (99.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDays of phototherapy - median [IQR]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0 [1.0, 4.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.0 [0.0, 0.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0 [2.0, 4.0]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRespiratory distress syndrome - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1042 (69.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e145 (57.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e897 (71.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSevere intraventricular hemorrhage - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e82 (5.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (4.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e70 (5.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.726\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBronchopulmonary disease - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73 (11.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 (7.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64 (12.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.142\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNecrotizing enterocolitis - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e155 (10.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32 (12.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e123 (9.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.227\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHemodynamically patent ductus arteriosus - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e438 (29.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e75 (29.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e363 (29.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.866\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEarly-onset sepsis - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53 (3.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 (4.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42 (3.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.563\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLate-onset sepsis - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e352 (23.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55 (21.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e297 (23.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.516\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDeath - n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e139 (9.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30 (11.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e109 (8.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.149\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eIQR: interquartile range; n: number; SD: standard deviation; \u003csup\u003ea\u003c/sup\u003et-test, \u003csup\u003eb\u003c/sup\u003eχ\u003csup\u003e2\u003c/sup\u003etest, \u003csup\u003ec\u003c/sup\u003eMann-Whitney U test.\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe mean (SD) GA of the overall population was 29.9 (2.8) weeks, and the mean BW was 1199.7 (372.5) grams. Infants with hyperbilirubinemia had an average of 1-week lower GA and 60 grams less BW than patients without hyperbilirubinemia (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 and p\u0026thinsp;=\u0026thinsp;0.012, respectively).\u003c/p\u003e \u003cp\u003eThere was no difference in sex between infants with and without hyperbilirubinemia. However, the non-hyperbilirubinemia group had more infants who were SGA or outborn. Infants born to mothers who had preterm premature rupture of membranes or cesarean deliveries had higher rates of hyperbilirubinemia. APGAR scores were similar in both groups at the 1st and 5th minutes, but the hyperbilirubinemia group had slightly higher IQR at 10 minutes. More than 70% of neonates with hyperbilirubinemia developed RDS, resulting in increased use of non-invasive ventilation and prolonged oxygen therapy. Infants with hyperbilirubinemia received more RBC transfusions, although exchange transfusion rates were similar in both groups. The incidence of all other analyzed neonatal outcomes was similar in both groups.\u003c/p\u003e \u003cp\u003eIn the total population, 12.8% of the infants had ROP. The rate of any ROP was higher in the infants with hyperbilirubinemia (13.8%) when compared with the infants without hyperbilirubinemia (7.8%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). The rates of non-severe and severe ROP in the groups with and without hyperbilirubinemia were (8.0% vs. 3.9% and 5.8% vs. 3.9%).\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the median number of days of exposure to hyperbilirubinemia was significantly higher in infants with any ROP compared to infants without ROP (3 days [IQR: 2 to 5] vs. 2 days [IQR: 1 to 4], p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Furthermore, the significant difference in days of exposure to hyperbilirubinemia was maintained when the non-ROP group was compared to both the non-severe ROP and severe ROP groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe results of the Poisson regression model, adjusted for GA, sex, and SGA, showed that infants exposed to hyperbilirubinemia had a higher risk of developing any grade of ROP. Each additional day of hyperbilirubinemia increased the risk of developing any ROP by 5%, non-severe ROP by 4%, and severe ROP by 6% compared to the group without ROP (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Finally, in the analysis conducted on the sub-population with GA less than 27 weeks and/or BW less than 1000 g, it was observed that the days of hyperbilirubinemia were not associated with ROP in either the crude or adjusted models (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePoisson regression models\u0026rsquo; results between days of hyperbilirubinemia and ROP for the overall population\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eCrude\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eAdjusted *\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Any ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.997; 1.154\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.060\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.008; 1.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,016\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Non-Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.986; 1.111\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.137\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.001; 1.073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,043\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.987; 1.147\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.103\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.023; 1.099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-Severe ROP vs. Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.980; 1.079\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.969; 1.056\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003eROP: Retinopathy of Prematurity; RR: risk ratio; CI: confidence interval; *adjusted for gestational age, sex, and small for gestational age\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePoisson regression models\u0026rsquo; results between days of hyperbilirubinemia and ROP for patients with GA\u0026thinsp;\u0026lt;\u0026thinsp;27 weeks and BW\u0026thinsp;\u0026lt;\u0026thinsp;1000 g\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGA\u0026thinsp;\u0026lt;\u0026thinsp;27 weeks and BW\u0026thinsp;\u0026lt;\u0026thinsp;1000 g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eCrude\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eAdjusted*\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ep\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Any ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.978; 1.314\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.095\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.97; 1.277\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,128\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Non-Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.972; 1.241\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.132\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.978; 1.208\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,123\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo ROP vs. Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.975; 1.287\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.971; 1.274\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,125\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-Severe ROP vs. Severe ROP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.966; 1.073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.498\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1,02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.95; 1.093\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,600\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"7\" nameend=\"c7\" namest=\"c1\"\u003e \u003cp\u003eBW: birth weight; CI: confidence interval; GA: gestational age; ROP: Retinopathy of Prematurity; RR: risk ratio; *adjusted for gestational age, sex, and small for gestational age\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe potential role of bilirubin in the pathogenesis of ROP is controversial. It has been suggested that bilirubin is protective against ROP due to its antioxidant effects [50; 51], but also that hyperbilirubinemia is a risk factor for the development of ROP [20\u0026ndash;29; 52\u0026ndash;54]. The results of our retrospective analysis in a cohort of 1526 very preterm infants are consistent with the second suggestion. Our study shows that hyperbilirubinemia requiring phototherapy is associated with an increased risk of developing ROP. However, the association between hyperbilirubinemia and ROP could not be observed in the subgroup with the lowest GA, which is more susceptible to developing severe ROP.\u003c/p\u003e \u003cp\u003eThe main limitations of our study are its retrospective nature and the lack of information on the actual bilirubin levels of the infants. Since our criterion for the definition of hyperbilirubinemia was the need for phototherapy, we cannot exclude a possible protective effect of moderate bilirubin levels against ROP in the group that did not require phototherapy. Currently, there is limited knowledge about what serum bilirubin levels are beneficial or detrimental, and studies have yielded conflicting results. Shahab et al. reported that TSB levels up to 20 mg/dl may protect term neonates from oxidative stress-related pathologies. However, the protective effect decreases above 20 mg/dl [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. Other studies suggest that TSB levels above 5.1 mg/dl may reduce the risk of severe ROP in neonates undergoing phototherapy [56; 57]. In contrast, by associating higher peak TSB levels with an increased risk of severe ROP, Milner et al. contradicted the protective role of bilirubin [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. It should also be noted that some investigators have questioned the antioxidant effects of neonatal bilirubin, demonstrating a negative correlation between serum bilirubin levels and antioxidant capacity [59; 60]. Dani et al. speculated that this is the result of the pro-oxidant effect of heme oxygenase mediated by iron release, which counteracts the antioxidant properties of bilirubin [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAnother limitation of our phototherapy-based definition of hyperbilirubinemia is its inability to separate the ocular effects of phototherapy from the ocular effects of hyperbilirubinemia. Of note, the wavelengths of light that are most efficient in decreasing bilirubin levels are also the wavelengths likely to produce retinal damage [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e]. Moreover, it has been suggested that some of the harmful effects of phototherapy on ROP may be related to its ability to reduce the antioxidant capacity of bilirubin [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e]. Therefore, by degrading bilirubin, phototherapy may decrease the capacity of oxidation resistance and may increase ROS in both the retina and serum [21; 62; 63].\u003c/p\u003e \u003cp\u003eThe association between length of phototherapy and risk of ROP was previously shown in a small study by Khatami et al. and has now been confirmed in a much larger cohort [\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e]. It is noteworthy that this association between the duration of phototherapy and the risk of developing ROP was not observed in the subgroup of infants with a GA of less than 27 weeks. This is the group that has the highest risk of developing ROP and is also the group that is most exposed to oxidative stress. Since ROP is a condition with multifactorial pathogenesis, we speculate that a factor such as hyperbilirubinemia may not make a difference in a population with a higher baseline risk of ROP. Accordingly, the association between hyperbilirubinemia and ROP has not been found in infants with higher GA [65; 66]. Finally, it should be noted that many of the risk factors for developing ROP are the same as those for developing severe hyperbilirubinemia [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e]. Thus, hyperbilirubinemia may be a surrogate for other risk factors for ROP rather than a risk factor itself. In conclusion, this retrospective study showed an association between hyperbilirubinemia requiring phototherapy and the risk of developing ROP in very preterm infants. However, association does not imply causation. ROP is a multifactorial condition, and it is difficult to determine the pathogenic role of individual risk factors. Our data suggest that high bilirubin levels, i.e., those requiring phototherapy, do not protect the developing retina from oxidative stress. It remains to be determined whether lower bilirubin levels have this protective antioxidant effect against ROP and other oxidative stress-mediated conditions of the preterm infant.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e S.G., G.R., M.B.M., G.A., M.F., F.G., S.O., E.V., and G.C. (Giacomo Cavallaro) contributed to the study’s conception and design; S.G., G.R., G.C. (Gaia Cervellini), M.C., V.T., F.G., E.V., and G.C. (Giacomo Cavallaro) contributed to the study’s methodology, investigation, and data curation; S.G., G.C. (Gaia Cervellini), M.C., V.T., M.B.M., and S.O. contributed to data collection; N.P. performed the statistical analysis; S.G., G.C. (Gaia Cervellini), G.R., M.B.M., and G.C. (Giacomo Cavallaro) wrote the initial draft preparation of the manuscript; S.G., G.R., G.C. (Gaia Cervellini), M.B.M., G.A., F.G., E.V., and G.C. (Giacomo Cavallaro) wrote, reviewed, and edited the manuscript; The co-first S.G. and G.C. (Gaia Cervellini), and co-last E.V. and G.C. (Giacomo Cavallaro) authorship contributed equally and have the right to list their name as first or last in their Curriculum Vitae. E.V. and G.C. (Giacomo Cavallaro) contributed equally to the visualization of the manuscript; G.C. (Giacomo Cavallaro) contributed to the supervision and project administration of the study. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This study was (partially) funded by the Italian Ministry of Health—Current Research IRCCS.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement:\u003c/strong\u003e The data presented in this study are available on request from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of Interest:\u003c/strong\u003e The authors declare that the research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCavallaro G, Filippi L, Bagnoli P, La Marca G, Cristofori G, Raffaeli G, Padrini L, Araimo G, Fumagalli M, Groppo M, Dal Monte M, Osnaghi S, Fiorini P, Mosca F (2014) The pathophysiology of retinopathy of prematurity: an update of previous and recent knowledge. 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Z Geburtshilfe Neonatol 207:24-28\u003c/li\u003e\n\u003cli\u003ePillai A, Pandita A, Osiovich H, Manhas D (2020) Pathogenesis and management of indirect hyperbilirubinemia in preterm neonates less than 35 weeks: moving toward a standardized approach. Neoreviews 21:e298-e307\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpe","sideBox":"Learn more about [European Journal of Pediatrics](https://www.springer.com/journal/431)","snPcode":"431","submissionUrl":"https://submission.nature.com/new-submission/431/3","title":"European Journal of Pediatrics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Newborn, jaundice, hyperbilirubinemia, retinopathy of prematurity, phototherapy","lastPublishedDoi":"10.21203/rs.3.rs-4241277/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4241277/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRetinopathy of prematurity (ROP) is a vasoproliferative retinal disease in preterm infants. Oxidative stress plays a key role in the pathogenesis of ROP. Bilirubin has been proposed to be protective against ROP due to its antioxidant effects. This study explored the association between hyperbilirubinemia and ROP.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe analyzed a 10-year cohort from a neonatal intensive care unit in Milan, Italy, including 1606 infants born under 32 weeks and/or \u0026lt; 1500 g.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData from 1606 infants meeting specific inclusion criteria were reviewed. Eighty infants were excluded due to lack of data, 1526 were deemed eligible for analysis, and 1269 had hyperbilirubinemia requiring phototherapy. There was a higher incidence of ROP among infants with hyperbilirubinemia (13.8%) versus those without (7.8%, p \u0026lt; 0.01). Infants with any ROP, non-severe or severe ROP, were exposed to hyperbilirubinemia for a significantly higher number of days compared with those without ROP. Each additional day of exposure increases the risk of developing any ROP by 5%, non-severe ROP by 4%, and severe ROP by 6%. However, this correlation was not observed in infants with gestational age less than 27 weeks and/or body weight less than 1000 g.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOur data show that hyperbilirubinemia requiring phototherapy is associated with an increased risk of developing ROP. However, severe hyperbilirubinemia and ROP share many of their risk factors. Therefore, rather than being a risk factor itself, hyperbilirubinemia may be a surrogate for other risk factors for ROP.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Trial Registration\u003c/strong\u003e: NCT05806684\u003c/p\u003e","manuscriptTitle":"Hyperbilirubinemia and Retinopathy of Prematurity: A Retrospective Cohort Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-17 19:59:02","doi":"10.21203/rs.3.rs-4241277/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-05-01T07:44:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-04-19T08:14:37+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"550dd1be-a4e5-428d-86ee-8d03643fa17c","date":"2024-04-13T10:02:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"90c4632e-58f5-43a9-b739-3fa144d8934e","date":"2024-04-12T18:23:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-12T16:33:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-11T14:45:57+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-11T14:44:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Pediatrics","date":"2024-04-09T10:38:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-pediatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejpe","sideBox":"Learn more about [European Journal of Pediatrics](https://www.springer.com/journal/431)","snPcode":"431","submissionUrl":"https://submission.nature.com/new-submission/431/3","title":"European Journal of Pediatrics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"540ef56d-e889-40bc-b5dd-20960d83ef7d","owner":[],"postedDate":"April 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-06-21T14:54:24+00:00","versionOfRecord":{"articleIdentity":"rs-4241277","link":"https://doi.org/10.1007/s00431-024-05630-3","journal":{"identity":"european-journal-of-pediatrics","isVorOnly":false,"title":"European Journal of Pediatrics"},"publishedOn":"2024-06-15 14:54:24","publishedOnDateReadable":"June 15th, 2024"},"versionCreatedAt":"2024-04-17 19:59:02","video":"","vorDoi":"10.1007/s00431-024-05630-3","vorDoiUrl":"https://doi.org/10.1007/s00431-024-05630-3","workflowStages":[]},"version":"v1","identity":"rs-4241277","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4241277","identity":"rs-4241277","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}