Level 2 (mid-level) evidence

Hypertensive disorders of pregnancy, which includes chronic hypertension, gestational hypertension, preeclampsia, preeclampsia superimposed on chronic hypertension, and eclampsia, are the most common medical complications of pregnancy and affect 5-8% of all pregnancies in the United States. Induction of labor was previously found to significantly reduce the risk of severe hypertension, with a nonsignificant decrease in incidence of both HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) and intensive maternal hospital care compared to expectant monitoring in women with gestational hypertension or mild preeclampsia at 36-41 weeks gestation (Lancet. 2009;374[9694]:979). Current guidelines recommend considering delivery in women with non-severe hypertensive disorders of pregnancy at > 37 weeks gestation and indicate earlier delivery with the presence of maternal or fetal distress, severe preeclampsia, or HELLP syndrome (Obstet Gynecol. 2013;122[5]:1122; J Obstet Gynaecol Can. 2014;36[5]:416). Recommendations are less clear, however, for women with non-severe hypertensive disorders of pregnancy at 34-37 weeks gestation. A recent randomized trial compared immediate delivery vs. expectant management in 703 women with non-severe hypertensive disorders of pregnancy at 34-37 weeks gestation. Immediate delivery included the induction of labor or cesarean delivery within 24 hours of randomization, while women randomized to expectant monitoring received interventions aimed at prolonging pregnancy until 37 weeks gestation (HYPITAT-II trial, Lancet. 2015;385[9986]:2492).

The median time between randomization and delivery was 2 days with immediate delivery vs. 7 days with expectant monitoring. In the expectant monitoring group, 36% of women delivered before 37 weeks gestation due to maternal or fetal indications. The composite outcome of maternal adverse events was defined as thromboembolic complication, pulmonary edema, HELLP syndrome, eclampsia, placental abruption, or maternal death. Although there were no significant differences in maternal adverse events between groups, there was a nonsignificantly lower rate of adverse events with immediate delivery compared to expectant monitoring (1.1% vs. 3.1%). There were no significant differences in individual maternal complications including HELLP syndrome, thromboembolic process, or eclampsia. Immediate delivery was associated with increased adverse neonatal outcomes, however. Neonatal respiratory distress syndrome occurred in 5.7% of infants with immediate delivery vs. 1.7% with expectant monitoring (NNH 25) and neonatal morbidity was reported in 49.1% of immediate deliveries vs. 36.3% of monitored pregnancies (NNH 8).

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While this trial did not find that immediate delivery was associated with a significant decrease in overall maternal complications, these results are limited by the low number of maternal adverse events in both groups as well as the high rate of delivery before 37 weeks in the expectant monitoring group. However, the increased risk of neonatal adverse events was clear, with a significant increase in the rates of neonatal respiratory distress syndrome and overall neonatal morbidity in the immediate delivery group. These results suggest that expectant management for women at 34-37 weeks gestation with non-severe hypertensive disorders may result in better outcomes for the baby, but the question of possible increase in adverse maternal outcomes will need to be evaluated in subsequent trials.

Alan Ehrlich, MD, is a deputy editor for DynaMed, Ipswich, Mass., and assistant clinical professor in Family Medicine, University of Massachusetts Medical School in Worcester. 

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