814: Nulliparous women in the second stage of labor: changes in neonatal outcomes over the past 10 years stratified by mode of delivery

To evaluate changes over the past decade in neonatal outcomes for infants delivered to nulliparous women who reached the second stage of labor. We conducted a retrospective cohort study of all nulliparous women at our institution with singleton gestations ≥36 weeks who reached complete dilation from January 1, 2011-December 31, 2012 and compared these data to a prior cohort study conducted at the same institution from July 28, 2000-February 28, 2003. We excluded pregnancies with prenatally diagnosed fetal anomalies. In the study’s primary analysis, we found that for current patients, spontaneous vaginal delivery (SVD) occurred more often, operative vaginal delivery (OVD) occurred less often, and cesarean delivery (CD) occurred more often (all p<0.01). For the current analysis, we evaluated whether the cohorts differed in terms of mean arterial cord pH and composite neonatal morbidity (neonatal death, intrapartum fetal death, 5-minute Apgar <4, arterial pH <7.00, mechanical ventilation, necrotizing enterocolitis, culture-confirmed sepsis, grade III/IV intraventricular hemorrhage, skull fracture, subgaleal bleed, seizures, and brachial plexus injury). These outcomes were stratified by mode of delivery. In the prior cohort, there were 1023 women—77% had an SVD, 21% had an OVD and 2% had a CD. In the current cohort, there were 1476 women—84% had an SVD, 10% had an OVD and 6% had a CD. See the table for comparison of mean arterial cord pH and rate of composite neonatal morbidity overall and stratified by mode of delivery. Arterial cord pH did not differ between cohorts overall or when stratified by mode of delivery. The odds of composite neonatal morbidity was higher in the current cohort and persisted in the multivariable model (AOR 2.06; 95% CI 1.02-4.12). Compared to 10 years ago, infants delivered to nulliparous women who reach the second stage of labor do not have a difference in arterial cord pH but do have an increased odds of morbidity.