Late pregnancy complications can affect risk estimates of elective induction of labor

Objective. Multiple observational studies have emphasized the increased risk of elective induction versus spontaneous labor. We estimated the risks of elective induction before 39 weeks compared to expectant management. Methods. Using a single institution's delivery data (1996-2004), we identified women with uncomplicated term gestations who underwent elective induction before 39 weeks (Early Induction Group). A comparison group of women eligible for elective induction before 39 weeks but who were managed expectantly was created by identifying the remaining deliveries ≥39 weeks and excluding women with "established" pregnancy complications such as diabetes or heart disease (Expectant Management Group), but retaining women with complications that may have developed while waiting, e.g. gestational hypertension or abruption. Results. Pregnancies in the Early Induction Group were generally not at increased risk for morbidity when compared to the entire Expectant Management Group, in whom 49% developed pregnancy complications or went postdates. These pregnancies had poorer maternal and neonatal outcomes when compared to patients who remained uncomplicated with spontaneous labor onset, thus reducing the overall benefit of expectant management. Conclusions. Failure to account for the large proportion of women who develop late pregnancy complications can falsely elevate the estimated risk of elective induction prior to 39 weeks.