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