O2108: Impact of Labor Before Delivery on Necrotizing Enterocolitis in Preterm Infants: A Single Center Analysis

Background: Necrotizing enterocolitis (NEC) is a serious complication for premature infants, with a mortality rate of 15-30%. The etiology of NEC is multifactorial and evidence suggests the gut microbiome may play a role. Studies show distinct differences in the microbiome of neonates born via cesarean section versus vaginal delivery. New data suggests that exposure to labor prior to cesarean delivery further shapes early microbial colonization via exposure to vaginal flora. While studies have shown that mode of delivery has not been associated with NEC, none have examined whether labor preceding delivery impacts the risk of NEC. This study hypothesizes that premature infants delivered via cesarean section with no labor before delivery have increased risk of NEC, compared to those exposed to labor before delivery.

Methods: This single center retrospective cohort study analyzed data from the Vermont Oxford Network database and medical records on preterm infants born at 23 0/7- to 34 6/7-weeks' gestation with birth weight below 1500 grams at our institution. Outborn infants and infants with congenital anomalies were excluded. Fisher’s exact test compared categorical variables, while the Kruskal-Wallis test analyzed quantitative variables. Multivariable logistics regression analysis was conducted to compare outcomes after controlling for statistically significant characteristics. Labor was defined as the presence of uterine contractions resulting in cervical dilation or effacement. In cases where no cervical exam was documented, regular contractions for one hour or more immediately prior to delivery was used as a proxy, assuming cervical change had occurred. ‘Labor before delivery’ included infants born vaginally and those born via cesarean section that met the study definition of labor.

Results: Of the 1344 charts reviewed, 791 (58.9%) infants were exposed to labor before delivery, while 553 (41.2%) were not. Table 1 shows maternal and infant characteristics for each group. Groups differed significantly by gestational age, birth weight, presence of chorioamnionitis, multiple gestation, and small for gestational age. Infants exposed to labor had significantly lower odds of NEC (odds ratio = 0.570, 95% confidence interval: 0.365 – 0.890, p = 0.015), compared to those who were not exposed to labor. This association remained significant after controlling for gestational age, small for gestational age, multiple gestation, and chorioamnionitis (adjusted odds ratio = 0.538, 95% confidence interval: 0.328 – 0.883, p = 0.014) (Figure 2).

Conclusion: Absence of maternal labor prior to delivery is a newly identified association for NEC in very low birth weight premature infants, offering potentially novel insights into its perinatal and microbial pathogenesis. These findings highlight the importance of perinatal microbial exposures and suggest new avenues for NEC risk stratification and prevention. Further translational research may elucidate the impact of labor on the microbiome and its direct linkage to the incidence of NEC.