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Induction of labor after 37 weeks recommended for women with gestational hypertension/mild pre-eclampsia (Hypitat study)


Pregnant women with mild hypertensive disorders such as high blood pressure/mild pre-eclampsia^ should have their labour induced once they complete 37 weeks of their pregnancy. This is the conclusion of the HYPITAT study, published in an Article Online First and in an upcoming edition of The Lancet, written by Dr Corine M Koopmans, Department of Obstetrics and Gynaecology, University Medical Centre Groningen, Netherlands, and colleagues.

About 6𔃆% of pregnancies are complicated by hypertensive disorders such as gestational hypertension (high blood pressure) and mild pre-eclampsia. Such disorders in pregnancy make a substantial contribution to maternal and neonatal morbidity and mortality worldwide. In the Netherlands these disorders are the primary cause of maternal mortality. 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. In the USA and other developed countries, induction of labour is already clinical practice in women with gestational hypertension or mild pre-eclampsia, but, until this study, this treatment was not based on the results of randomised clinical trials. However, in The Netherlands, expectant monitoring is the protocol in most hospitals.

This study looked at 756 pregnant women from 38 centres in The Netherlands, all with singleton pregnancies and at 36--41 weeks' gestation, and all of whom had gestational hypertension or mild pre-eclampsia. They were randomised in a 1:1 ratio to induced labour or expectant monitoring. The primary outcome was any of a variety of measures of poor maternal outcome--death, eclampsia, HELLP syndrome*, pulmonary oedema**, thrombembolic disease, placental abruption***, progression to severe high blood pressure or proteinuria****, and major post-birth bleeding (of 1.0 litres or more). 397 women refused randomisation but allowed use of their medical records. The researchers found that, of the remaining women, 31% of those who were induced developed poor maternal outcome, compared with 44% who had expectant monitoring. Put another way, women who were induced had a 29% lower relative risk of developing poor maternal outcome than those who had expectant monitoring. No cases of maternal or newborn deaths were recorded in either group.

Surprisingly, fewer caesarean sections were needed in the induction group than in the expectant monitoring group. This result is of major importance, because women with a previous caesarean section are at increased risk of developing a uterus scar rupture in a next pregnancy. This can be life-threatening for both mother and child. Furthermore, women with a previous caesarean section will have a higher risk of caesarean section in the next pregnancy. Women with a caesarean section also need a longer recovery time with higher costs as compared to women with a spontaneous delivery. And quality of life is better in women who have a spontaneously delivery as compared to women who undergo a caesarean section.

The authors say: "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. 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."

They conclude: "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."

In an accompanying Comment, Dr Donna D Johnson, Medical University of South Carolina, Charleston, USA, says: "Inclusion of less serious pregnancy outcomes makes this trial even more clinically relevant. Is the goal of managing mild hypertensive disease at term to prevent rare serious maternal and fetal events, or to prevent overall deterioration of maternal health? The latter--the health of the mother--should be the goal of the obstetrician."

She concludes: "Severe hypertension and use of antihypertensive drugs were less common in the group of patients that had induction of labour. Thus this group had a lower probability of developing complications associated with severe hypertension. Therefore it is reasonable to treat mild hypertensive disease definitively with delivery rather than allow pregnancy to progress and blood pressure to increase if maternal caesarean section rate and neonatal morbidity are indeed unchanged."


Dr Corine M Koopmans, Department of Obstetrics and Gynaecology, University Medical Centre Groningen, Netherlands T) +31 50 36 13 020 E)

Dr Donna D Johnson, Medical University of South Carolina, Charleston, USA T) +1 843 735 9976 E)

For full Article and Comment, see:

Notes to editors:

^Pre-eclampsia is a medical condition where hypertension arises in pregnancy (pregnancy-induced hypertension) in association with significant amounts of protein in the urine.

^^Expectant monitoring=women monitored until spontaneous delivery or medical indication delivery. Frequent blood pressure, urine monitoring and tests for woman; fetal heart rate/movements also monitored.

*HELLP=haemolysis, elevated liver enzymes and low platelet (red blood cell) count.

**Pulmonary oedema=fluid accumulation in the lungs. This leads to impaired gas exchange and may cause respiratory failure.

***Placental abruption=where the placental lining has separated from the uterus of the mother. It is the most common cause of late pregnancy bleeding.

****Proteinuria=excess proteins in the urine.

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