Elsevier

The Lancet

Volume 374, Issue 9694, 19–25 September 2009, Pages 979-988
The Lancet

Articles
Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): a multicentre, open-label randomised controlled trial

https://doi.org/10.1016/S0140-6736(09)60736-4Get rights and content

Summary

Background

Robust evidence to direct management of pregnant women with mild hypertensive disease at term is scarce. We investigated whether induction of labour in women with a singleton pregnancy complicated by gestational hypertension or mild pre-eclampsia reduces severe maternal morbidity.

Methods

We undertook a multicentre, parallel, open-label randomised controlled trial in six academic and 32 non-academic hospitals in the Netherlands between October, 2005, and March, 2008. We enrolled patients with a singleton pregnancy at 36–41 weeks' gestation, and who had gestational hypertension or mild pre-eclampsia. Participants were randomly allocated in a 1:1 ratio by block randomisation with a web-based application system to receive either induction of labour or expectant monitoring. Masking of intervention allocation was not possible. The primary outcome was a composite measure of poor maternal outcome—maternal mortality, maternal morbidity (eclampsia, HELLP syndrome, pulmonary oedema, thromboembolic disease, and placental abruption), progression to severe hypertension or proteinuria, and major post-partum haemorrhage (>1000 mL blood loss). Analysis was by intention to treat and treatment effect is presented as relative risk. This study is registered, number ISRCTN08132825.

Findings

756 patients were allocated to receive induction of labour (n=377 patients) or expectant monitoring (n=379). 397 patients refused randomisation but authorised use of their medical records. Of women who were randomised, 117 (31%) allocated to induction of labour developed poor maternal outcome compared with 166 (44%) allocated to expectant monitoring (relative risk 0·71, 95% CI 0·59–0·86, p<0·0001). No cases of maternal or neonatal death or eclampsia were recorded.

Interpretation

Induction of labour is associated with improved maternal outcome and should be advised for women with mild hypertensive disease beyond 37 weeks' gestation.

Funding

ZonMw.

Introduction

About 6–8% of pregnancies are complicated by hypertensive disorders.1, 2 Such disorders in pregnancy make a substantial contribution to maternal and neonatal morbidity and mortality worldwide.3 In the Netherlands these disorders are the primary cause of maternal mortality.4, 5 Most hypertensive disorders present after 36 weeks' gestation. For the management of women with gestational hypertension or mild pre-eclampsia at term, evidence for selection of induction of labour versus expectant monitoring is scarce. Induction of labour is thought to prevent severe maternal and neonatal complications such as eclampsia, HELLP syndrome (haemolysis, elevated liver enzymes, and low platelet count), placental abruption, maternal death, and asphyxia. Conversely, induction might increase the risk of instrumental vaginal delivery and caesarean section, and thereby generate additional morbidity and costs.6, 7, 8

To our knowledge, no randomised clinical trial on this subject has yet been published. Strong practice variation exists in the Netherlands for treatment of women with gestational hypertension or mild pre-eclampsia beyond 36 weeks' gestation. Therefore we aimed to assess whether induction of labour in such women reduces poor maternal outcome compared with expectant monitoring.

Section snippets

Patients

We did a multicentre, parallel, open-label randomised controlled trial in the Netherlands, in which six academic and 32 non-academic hospitals participated. We recruited women with a singleton pregnancy and a fetus in cephalic presentation at a gestational age of between 36 (0 days) and 41 weeks (0 days), and who had gestational hypertension or mild pre-eclampsia. Gestational hypertension was defined as diastolic blood pressure of 95 mm Hg or higher measured on two occasions at least 6 h apart.

Procedures

Patients allocated to induction of labour were induced within 24 h of randomisation. If the patient had a Bishop score13 of more than 6 at vaginal examination, labour was induced with amniotomy and, if needed, augmentation with oxytocin. If the Bishop score was 6 or lower, cervical ripening was stimulated with intracervical or intravaginal prostaglandins or a balloon catheter. Use of oxytocin or prostaglandins depended on local protocols, which were based on national guidelines of the Dutch

Results

Between October, 2005, and March, 2008, we identified 1153 eligible women, of whom 756 gave informed consent for randomisation. We randomly assigned 377 patients to induction of labour and 379 to expectant monitoring (figure 1). Of the 397 patients who refused randomisation, most (82%) had expectant monitoring and only 18% had induction of labour. Baseline characteristics of all eligible women (table 1) showed that women in the randomised group, compared with those in the non-randomised group,

Discussion

The results of this study show that induction of labour was associated with a lower composite risk of poor maternal outcome, which was mainly ascribed to progression to severe disease, than was expectant monitoring. Overall, 13 per 100 fewer women allocated to induction of labour had a poor maternal outcome, corresponding with a number needed to treat of eight. Surprisingly, fewer caesarean sections were needed in the induction group than the expectant monitoring group. Adverse neonatal

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