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Poster Session I Thursday, February 14 • 10:45 AM - 12:00 PM • Octavius Ballroom • Caesars Palace| Volume 220, ISSUE 1, SUPPLEMENT , S100-S101, January 01, 2019

128: Maternal and perinatal outcomes by gestational age with expectant management of full-term low -risk nulliparas

      Objective

      To compare risks of selected maternal and perinatal outcomes by completed week of gestation (GA) after 39 weeks in low-risk nulliparas undergoing expectant management (EM).

      Study Design

      Planned secondary analysis of a multicenter RCT of induction of labor (IOL) at 390/7 wks vs. EM until at least 405/7 wks but no later than 422/7 in low-risk nulliparas. Only women with non-anomalous neonates, who were randomized to and proceeded with EM, and who attained 390/7 wks were included in this analysis. Delivery GA was categorized by completed wk (39, 40 and ≥41) and by labor mode (spontaneous vs. medically-indicated). Outcomes were: a) maternal, including cesarean (CD) and an adverse composite outcome and b) perinatal outcomes, including a perinatal composite and NICU admission. Categorical variables were compared using Cochran-armitage trend or Chi-Square test, and continuous variables using a Jonckheere Terpstra test. For multivariable analysis we applied Poisson regression.

      Results

      A total of 2518 women met eligibility criteria for this analysis. Overall, 39% delivered at 39 wks, 44% at 40 wks (73% of all remaining) and 17% at ≥41 wks (Table 1). Spontaneous labor occurred in 62.3%. The prevalence of medically- indicated delivery (including post-dates) increased with GA (Table 1). Apart from postdates, hypertensive disorders of pregnancy (HDP) and PROM were the most common indications for delivery at 39 and 40 wks. Baseline characteristics differed by delivery GA (Table 1), with the frequencies of Bishop score <5 and smoking, and the medians of age and BMI increasing with GA. The frequency of CD and the perinatal composite increased with increasing GA (Table 2). Additionally, when comparing outcomes of deliveries at each GA vs. deliveries at subsequent GAs (aRR; 95% CI), CD was significantly lower at 39 wks (0.68; 0.58, 0.80) and 40 wks (0.64; 0.55, 0.76).