performed to determine the frequencies and strength of association of perinatal mortality and parity, adjusting for maternal age, race, BMI, pre-gestational diabetes, chronic hypertension, fetal sex, smoking status, and socioeconomic status. A p-value less than 0.05 was used to indicate statistical significance. RESULTS: Of 1,317,761 total deliveries, 765,995 (58.1%) were nulliparous and 551,766 (41.9%) were multiparous with one prior birth. Nulliparous women had significantly increased rates of IUFD (aOR 3.30, 95% CI 2.93-3.72) and NND (a OR 1.54, 95% CI 1.19-1.98) compared to multiparous women even after adjusting for relevant covariates. Compared to multiparous women, nulliparous women also had increased rates of small-for-gestational (SGA) age infants at <10% birth weight (aOR 1.76, 95% CI 1.72-1.79) (Figure 1) and Apgars <7 at 5 minutes (aOR 2.42, 95% CI 2.27-2.57). See Table 1 for adverse neonatal outcomes. CONCLUSION: Perinatal mortality is significantly greater in nulliparous women compared to multiparous women with term deliveries. There may be a role to focus on improving maternal health to maximize physiologic adaptation. These findings suggest that lowrisk nulliparous women may require increased surveillance and future studies are needed to determine if interventions during pregnancy can improve neonatal outcomes.

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Objective This study aimed to evaluate if maternal serum hormones along the maternal–fetal hypothalamic–pituitary–adrenal (HPA) axis, when drawn prior to labor induction, differed between women who delivered vaginally and those who underwent cesarean. Study Design This was a prospective observational study at a single perinatal center performed from August 2017 to May 2018. Nulliparous women with uncomplicated singleton pregnancies ≥39 weeks had maternal serum collected prior to induction. Corticotrophin-releasing hormone (CRH) was measured by ELISA; dehydroepiandrosterone sulfate (DHEA-S), cortisol, estriol (E3) estradiol (E2), and progesterone (P4) were measured by chemiluminescent reaction. Mean analyte concentrations as well as three ratios (E2/P4, E3/P4, and E2/E3) were compared between women who had a vaginal versus cesarean delivery. Logistic regression was used to model the relationship between CRH and the odds of vaginal birth. We estimated that a sample size of 66 would have 90% power to detect a 25% difference in mean CRH levels assuming a vaginal:cesarean ratio of 2:1 with a baseline CRH concentration of 140 (standard deviation = 36) pg/mL. Results Of the 88 women who had their serum analyzed, 27 (31%) underwent cesarean. Mean maternal serum CRH levels were similar between the vaginal delivery and cesarean groups (122.6 ± 95.2 vs. 112.3 ± 142.4, p = 0.73). Similarly, there were no significant differences in any other maternal serum analytes or ratios. Logistic regression showed a nonsignificant odds ratio for successful vaginal birth (p = 0.69) even when evaluating only the 16 women who had a cesarean for an arrest disorder (p = 0.08). Conclusion In low-risk nulliparous women undergoing full-term labor induction, there were no differences noted in a broad array of other maternal-fetal HPA-axis hormones between women who had a vaginal or cesarean delivery.

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