1138 Predicting spontaneous labor beyond 39 weeks among expectantly managed gravidas

Abstract

Elective induction of labor (IOL) at 39 weeks is associated with a lower risk of cesarean delivery (CD) and perinatal morbidity compared to expectant management (EM). Among women expectantly managed, some will labor spontaneously and others will eventually require IOL. We sought to identify characteristics associated with spontaneous labor onset (SL) in women undergoing EM>39 weeks and the associated perinatal risks. Retrospective cohort of singleton pregnancies ≥39 0/7 delivered at a single center in 2013. Exclusion criteria were presence of an obstetric indication precluding EM≥390/7, elective IOL, hypertensive disorder of pregnancy 1 prior CD, elective CD or fetal anomaly/demise. Predictor variables included prenatally available maternal demographic and clinical characteristics (Table). Multivariable logistic regression with backward selection was used to generate 2 parsimonious models- the main model excluded admission cervical dilatation given its temporality with labor; adjusted odds ratios, receiver operating characteristic curves and area under the curves (AUC) were reported. Mode of delivery, NICU admission >72hrs, respiratory distress syndrome, clinically diagnosed postpartum hemorrhage, chorioamnionitis and endometritis were compared between women who did and did not have SL. Of 707 eligible women, 536 (76%) attained SL. The first model included maternal BMI, parity and substance use as predictive variables and modestly predicted SL (Figure, AUC=0.68). Including admission cervical examination in the model significantly improved prediction of SL (Figure, AUC=0.94). Women achieving SL (vs not) had significantly lower odds of CD (OR 0.33 [0.21-0.53]) and NICU admission (OR 0.38 [0.15-0.94]); other outcomes were not significantly different between groups. CD and NICU admission risks are lower in women undergoing EM ≥390/7 with SL. Contingent on external validation, our model can modestly predict SL >39 weeks of gestation. Incorporating outpatient 3rd trimester cervical examination may improve model utility.View Large Image Figure ViewerDownload Hi-res image Download (PPT)