A risk of waiting: the weekly incidence of hypertensive disorders and associated maternal and neonatal morbidity in low-risk term pregnancies

BackgroundElective induction of labor (eIOL) prior to 39 weeks' gestation is discouraged because of presumed fetal benefits. However, few data exist on the maternal risks of expectant management. To date, no study has evaluated the maternal risk of developing a hypertensive disorder of pregnancy with expectant management of a low-risk gravid at term.ObjectiveWe sought to evaluate the development of hypertensive disorders in term low-risk expectantly managed patients.Study DesignThis is a retrospective cross-sectional study from 19 US hospitals, from 2002 to 2008 (Safe Labor Consortium) including all nonanomalous, cephalic, singleton pregnancies at 37-41 weeks. Women with a history of hypertension, diabetes mellitus, cardiovascular disease, or planned cesarean delivery or from centers with incomplete hypertensive data were excluded. Women with eIOL in each week were compared with women managed expectantly until the next week of gestation or beyond. The primary outcome was the frequency of hypertensive complications.ResultsOf 114,651 low-risk deliveries, 12,772 (11.1%) had eIOL. The cohort was 49.2% nulliparous, 51.1% white, and obese (mean body mass index 30.2 kg/m2). The risk of developing any hypertension in expectantly managed women was 4.1% after 37 weeks, 3.5% after 38 weeks, 3.2% after 39 weeks, and 2.6% after 40 weeks. Compared with eIOL, women with hypertensive disorders had significantly higher rates of cesarean delivery and maternal morbidities (intensive care unit admission or death, third- or fourth-degree lacerations, maternal infections, and bleeding complications) at each week of gestation and the composite neonatal morbidity at 38 and 39 weeks of gestation.ConclusionFor women at low risk expectantly managed at term, there is a risk of developing hypertensive complications for each additional week of pregnancy, with associated increases in maternal and neonatal morbidities.