Labor Induction at 37 Weeks Recommended for Women With Mild Hypertensive Disorders

From Medscape Medical News
Laurie Barclay, MD

August 11, 2009 — Pregnant women with mild hypertensive disorders should have labor induced once they complete 37 weeks of pregnancy, according to the results of a multicenter, parallel, open-label, randomized controlled trial reported online in the August 4 issue of The Lancet.

"Robust evidence to direct management of pregnant women with mild hypertensive disease at term is scarce," write Corine M. Koopmans, MD, from University Medical Centre Groningen in Groningen, the Netherlands, and colleagues from the HYPITAT study group (Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks’ gestation). "We investigated whether induction of labour in women with a singleton pregnancy complicated by gestational hypertension or mild pre-eclampsia reduces severe maternal morbidity."

At 6 academic and 32 nonacademic hospitals in the Netherlands, patients with a singleton pregnancy at 36 to 41 weeks' gestation, and who had gestational hypertension or mild preeclampsia, were enrolled between October 2005 and March 2008. With use of block randomization with a Web-based application system, participants were assigned in a 1:1 ratio to induced labor or expectant monitoring. It was not possible to mask participants' assignments.

The main endpoint of the study was a composite measure of poor maternal outcome, including maternal mortality, maternal morbidity, progression to severe hypertension or proteinuria, and major postpartum hemorrhage (> 1000 mL of blood loss), with analysis by intent-to-treat and treatment effect presented as relative risk (RR). Maternal morbidity was defined as eclampsia, HELLP syndrome (hemolysis, elevated liver enzymes, and low platelet count), pulmonary edema, thromboembolic disease, and placental abruption.

Of 756 patients randomized, 377 were assigned to receive labor induction and 379 to expectant monitoring. In addition, 397 patients authorized medical record review but refused randomization.

Poor maternal outcome occurred in 117 (31%) of women who were randomly assigned to induction of labor and in 166 (44%) of those randomly assigned to expectant monitoring (RR, 0.71; 95% confidence interval [CI], 0.59 - 0.86; P < .0001). There were no recorded cases of maternal or neonatal mortality or eclampsia.

Fewer cesarean deliveries were needed in the induction group vs the expectant monitoring group.

"Induction of labour is associated with improved maternal outcome," the study authors write. "We believe that induction of labour should be advised for women with gestational hypertension and a diastolic blood pressure of 95 mm Hg or higher or mild pre-eclampsia at a gestational age beyond 37 weeks."

Limitations of this study include absence of some useful data from the National Dutch Perinatal Registry.

"The results of our trial are important for both developed countries in which induction of labour in women with hypertensive disease beyond 36 weeks' gestation has been controversial, and for developing countries in which maternal morbidity and mortality rates are substantially increased," the study authors conclude. "Our finding that induction of labour was associated with a reduced risk of severe hypertension or HELLP syndrome and subsequent reduced need for caesarean section, emphasises the importance of frequent blood pressure monitoring during the concluding weeks of pregnancy."

In an accompanying comment, Donna D. Johnson, MD, from the Medical University of South Carolina in Charleston, notes that findings of this trial are even more clinically meaningful because less serious pregnancy outcomes were included. She recommends that overall management of maternal health be a primary goal of the obstetrician.

"In a subgroup analysis, composite maternal morbidity was not improved by induction of labour at this gestational age (36–37 weeks)," Dr. Johnson writes. "Although the study was not powered to detect differences at each gestational age, we should be hesitant to induce labour in women before 37 weeks of gestation for mild pre-eclampsia or gestational hypertension. By contrast, induction of labour at 37 weeks' gestation and beyond seems to improve obstetric outcomes in patients with gestational hypertension and pre-eclampsia, and this approach should be incorporated into clinical practice."

ZonMw, the Netherlands organization for health research and development, programme Doelmatigheidsonderzoek, supported this study. The study authors and Dr. Johnson have disclosed no relevant financial relationships.

Lancet. Published online August 4, 2009.