Risk of Expectant Management and Optimal Timing of Delivery in Low-Risk Term Pregnancies: A Population-Based Study

The benefits of the 39-week rule have been questioned and concerns of increased stillbirth after adoption of this rule have been raised. Whether expectant management risks outweigh the benefits of awaiting 39 weeks has not been studied. We analyze the risks of expectant management at term and the optimal timing for delivery.

All U.S. nonanomalous singleton term deliveries in 2013 were selected, excluding diabetes/hypertension, and low birth weight. Maternal/neonatal complications and stillbirth/infant death were compared among expectant management versus deliveries at each term gestational age. Logistic regression was used to calculate adjust odds ratios of complications according to delivery plan at each gestational age.

From approximately 3 million deliveries, maternal complications during expectant management were lower at early term, and became higher at 39 weeks, relative risk [RR] (95% confidence interval [CI]) = 1.18 (1.16-1.19). Neonatal complications during expectant management were lower during early term, and became higher at ≥39 weeks, RR (95% CI) = 1.09 (1.08-1.09). The risk of perinatal mortality in the expectant management group was lower during early term, and became higher at ≥39 weeks, 18.93 (17.83-20.10) versus 17.37 (16.61-18.16), p = 0.010.

Complications during expectant management occurring while awaiting full term do not outweigh the benefits of better outcomes from reaching 39 weeks. However, extending beyond 39 weeks may put these pregnancies at an increased risk.