Treating chronic mild hypertension during pregnancy leads to better outcomes

The multicentre, randomised CHAP trial showed that aggressively targeting blood pressure in pregnant women with mild chronic hypertension to be <140/90 mmHg provided better pregnancy outcomes, with no consequent harm to either mothers or babies.

Presented by Prof. Alan Tita (University of Alabama, AL, USA), the Chronic Hypertension and Pregnancy (CHAP) trial (NCT02299414) aimed to assess the safety and efficacy of avoiding adverse pregnancy outcomes by treating pregnant women with mild chronic hypertension [1]. Prof. Tita pointed out that this is the largest, most diverse study conducted in pregnant women to date to address this major clinical question that has been debated for decades. The results were published simultaneously in the New England Journal of Medicine [2].

Enrolled were 2,408 women pregnant with a single foetus at <23 weeks of gestation. They were randomised to receive either antihypertensive treatments recommended for use in pregnancy (treatment group) or no treatment except in the case of severe hypertension (i.e. systolic pressure ≥160 mmHg or diastolic pressure ≥105 mmHg; control group). The primary efficacy endpoint was a composite of preeclampsia with severe features, medically indicated preterm birth <35 weeks gestation, placental abruption, or foetal/neonatal death. The safety endpoint was birth weight <10^th percentile for gestational age.

Both the efficacy and safety endpoints were met. In the treatment group, 30.2% of women experienced an efficacy primary-outcome event, as opposed to 37% of pregnancies in the control group (HR 0.82; 95% CI 0.74–0.92; P<0.001). Importantly, this benefit was not coupled with a negative impact on gestational-age birth weights; the incidence of <10^th percentile-for-gestational-age birth weights was 11.2% for the treatment group compared with 10.4% for the control group [risk ratio of 1.04, not significant]. The treatment group also had a modestly reduced incidence of serious maternal complications (2.1% and 2.8%, respectively; risk ratio 0.75; 95% CI 0.45–1.26) and severe neonatal complications (2.0% and 2.6%, respectively; risk ratio 0.77; 95% CI 0.45–1.30). Furthermore, the incidence of any preeclampsia favoured the treatment group at 24.4% and 31.1%, respectively (risk ratio 0.79; 95% CI 0.69–0.89), and the incidence of preterm birth was 27.5% and 31.4%, respectively (risk ratio 0.87; 95% CI 0.77– 0.99).

The take-home message from this trial is that treating pregnant women with mild chronic hypertension produces better pregnancy outcomes than a strategy of reserving treatment only for severe hypertension, with no increased risk of low foetal weight.

1. 
   
   1. Tita AT, et al. Antihypertensive Therapy For Mild Chronic Hypertension and Pregnancy Outcomes: A Pragmatic Multicenter RCT. Abstract 402–15, ACC 2022, 2–4 April, Washington DC, USA.
   2. Tita AT, et al. N Engl J Med 2022; 386:1781-1792.

 

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Posted on 15 June, 202224 June, 2022