Tighter prenatal hypertension control doesn’t result in larger babies, later births

Tight control of hypertension in pregnancy does not produce better perinatal outcomes or fewer serious maternal complications than looser control, according to results of an international randomized clinical trial. Published in the New England Journal of Medicine, the findings are consistent with those from a meta-analysis of 29 previous trials.

The Control of Hypertension in Pregnancy Study (CHPS) had no commercial sponsorship and was designed to compare less-tight control with tight control of nonproteinuric, nonsevere hypertension in pregnancy with respect to perinatal and maternal outcomes. The participants were 987 women at 14 weeks 0 days to 33 weeks 6 days gestation with nonproteinuric preexisting or gestational hypertension and office diastolic blood pressure (BP) of 90 to 105 mm Hg (85 to 105 mm Hg if taking antihypertensive medications) who had a live fetus. Randomization was to less-tight control (target diastolic BP 85 mm Hg). Pregnancy loss or high-level neonatal care for >48 hours during the first 28 postnatal days was the composite primary outcome; serious maternal complications up to 6 weeks postpartum or until hospital discharge (whichever was later) was the secondary outcome.

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No significant between-group differences were found in risk of pregnancy loss, high-level neonatal care, or overall maternal complications. Severe maternal hypertension was significantly more common, however, in the women with less-tight control of hypertension (P<0.001). Results for both outcomes were similar regardless of type of hypertension, use or non-use of antihypertensive medication at enrollment, presence or absence of gestational diabetes, the perinatal mortality ratio of the recruiting country, or whether adherence to the management algorithm was clinically reasonable. The study was powered at 80% at a two-tailed alpha level of 0.005, assuming primary outcome rates of 33% in the tight-control group and 25% in the group with looser control.

No antihypertensive drugs were provided by the study but labetalol was the drug of first choice for participants. ACE inhibitors, angiotensin-receptor antagonists, direct renin inhibitors, and atenolol were not permitted before delivery. Women in the looser-control group were less likely to take antihypertensive medication before (73.4% vs 92.6%, P<0.001) and after delivery (65.5% vs 78.3%; P<0.001).

Their trial, the authors said, was “substantially larger than previous trials that have examined effects of lower versus higher blood-pressure targets during pregnancy.” It was limited by inclusion of women with preexisting or gestational diabetes, but the researchers noted that the results for primary and secondary outcomes were similar for each hypertension type.

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