Introduction
Decisions regarding expectant management and timing of induction of labor must take into consideration both maternal and neonatal risks. Traditionally, it was believed that induction of labor prior to 41 weeks gestation is associated with increased maternal and neonatal risks.1,2 More specifically, several observational and retrospective cohort studies found that women who underwent induction of labor prior to 41 weeks gestation had an increased frequency of maternal and neonatal morbidity when compared to women who went into spontaneous labor at similar gestational ages.1-8 Thus, as a standard in obstetrical clinical management elective induction of labor in low-risk women was generally avoided before 41 weeks gestation because of a lack of neonatal benefits and adverse maternal outcomes.
Recent research has challenged this standard and current guidelines for low-risk women by more appropriately comparing the maternal, perinatal, and neonatal consequences of induction of labor at 39 weeks to those managed expectantly.9-21 Most of these studies have not shown a higher risk for adverse outcomes with labor induction at 39 weeks, except in cases of trial of labor after cesarean delivery.22 Some have shown that induction of labor resulted in more favorable maternal and perinatal outcomes than expectant management.15-19 However, many of these studies were very limited in sample size, studied specific age groups and were not powered to detect significant maternal and neonatal morbidities. 15-19 Similarly, the results of the randomized landmark studies, including the Walker et al. and the ARRIVE trial, were not completely consistent and didn’t provide definitive evidence of any potential advantages or disadvantages of labor induction at 39 weeks versus expectant management outside of a clinical trial.20,21 It is with these previously published findings in mind, that we designed the current national, large-scale retrospective cohort study