Abstract
Objective 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.
Study Design 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.
Results 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.
Conclusion 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.
Keywords
obstetric - delivery - pregnancy - complications - newborn - stillbirth - infant mortality
