There were fewer adverse pregnancy outcomes when pregnant women with mild chronic hypertension were treated with an antihypertensive medication before or during the first 20 weeks of pregnancy in the Chronic Hypertension and Pregnancy (CHAP) trial published in the New England Journal of Medicine.¹

A total of 2408 pregnant women with mild hypertension were enrolled in this multicenter trial, from 2015-2021. Of these, 1208 participants were assigned to treatment with antihypertensive medication to keep their blood pressure below 140/90 mm Hg (intervention group); the remaining 1200 received an antihypertensive only when the BP increased to 160/105 mm Hg and higher (control group). They were followed through delivery and for six weeks after delivery.

Results showed that treatment of hypertension to keep the BP below 140/90 mm Hg reduced the odds of preterm birth or other pregnancy-related complications. About 70% of women did not have any negative pregnancy outcomes, while 30% developed pre-eclampsia, placental abruption, preterm birth (<35 weeks) or intrauterine or neonatal death. About 37% of the participants in the control group experienced a similar adverse event.

The antihypertensive treatment had no adverse impact on fetal growth as the birth weight of infants was comparable between the two groups. Most of them had normal birth weight; 11% of babies born to participants who received medication and 10% of babies born to those in the control group had impaired fetal growth.

This study from the National Institutes of Health (NIH) shows that hypertension in pregnancy can be safely and effectively treated. Giving antihypertensive therapy to keep BP below 140/90 mm Hg in pregnant women with mild chronic hypertension is a feasible strategy rather than waiting to start treatment when hypertension increases to severe levels, according to the study. 

Reference

1. Tita AT, et al; Chronic Hypertension and Pregnancy (CHAP) Trial Consortium. Treatment for mild chronic hypertension during pregnancy. N Engl J Med. 2022 Apr 2. doi: 10.1056/NEJMoa2201295.