In the American College of Cardiology 2022 Scientific Session, Dr. Alan Tita from the University of Alabama at Birmingham, the United States (US), discussed the benefits of using antihypertensive therapy for mild chronic hypertension (CHTN) during pregnancy with good maternal and fetal outcomes.¹

CHTN in pregnancy is increasing, especially in Blacks and older patients with obesity at childbirth. It is associated with multiple maternal and fetal complications, such as death, preeclampsia, preterm birth (PTB), small for gestational age (SGA) infants, and cardiovascular (CV) morbidities.¹ According to the American College of Obstetrics and Gynecologists, CHTN in pregnancy is classified into severe, defined as blood pressure (BP) ≥160/110mmHg; and mild (non-severe), defined as BP=140-159/90-109mmHg and more prevalent.¹

Previous trials showed that the antihypertensive therapy in pregnant women with non-severe CHTN did reduce severe hypertension (HTN), but with no benefits for pregnancy outcomes and posed increased safety concerns due to an increase in SGA and low birthweight infants.¹ Moreover, randomized trials in pregnancy remain limited, underpowered and inappropriately designed, despite the antihypertensive therapy being recommended for non-pregnant patients, its benefits and safety in pregnancy are still uncertain, resulting in conflicting recommendations and controversies. ¹

Therefore, the Chronic Hypertension and Pregnancy (CHAP) project, an open-label and randomized controlled trial involving multiple US centers and the National Heart, Lung, and Blood institute (NHLBI), was designed to evaluate whether antihypertensive therapy for non-severe CHTN (target BP <140/90mmHg) during pregnancy would lead to a decrease in CHTN-associated outcomes without increasing the risk of SGA.¹

Patients with mild preexisting or newly diagnosed CHTN with singleton pregnancy at <23 weeks of gestation were included and randomized based on their BP as untreated or treated with monotherapy.¹ The active arm was treated with labetalol or nifedipine targeting a BP <140/90mmHg, whereas the standard arm had their BP therapy discontinued unless BP reached 160/105mmHg.¹ The primary endpoints included the composite of preeclampsia, PTB <35 weeks, abruption, and fetal or neonatal death, while the safety outcomes were SGA infants <10^th percentile and <5^th percentile.¹ The key secondary endpoints were maternal CV complications, preeclampsia, PTB, and serious neonatal comorbidities.¹

The baseline characteristics were similar in both groups which included 0.47% Blacks and 56% antihypertensive medications for preexisting CHTN, and a high proportion of obsess patients.¹  In addition to a significantly lower systolic and diastolic BP in the treatment arm, the primary outcome was shown to be significantly reduced by 18% (p<0.001).¹ Preeclampsia and PTB, the 2 components of the primary outcomes, were significantly reduced by 20% and 30%, respectively, in the treated group.¹ These results were consistent across the subgroups, and the safety outcome was similar in both groups.¹

Furthermore, the maternal outcomes of preeclampsia, HTN/organ dysfunction, and severe HTN and fetal outcomes of PTB and low birth weight were significantly reduced in the active arm compared with the standard arm.¹ Other maternal and neonatal outcomes did not differ between the 2 groups.¹

In conclusion, the CHAP project supported the treatment of CHTN in pregnant women and reduced adverse pregnancy outcomes, including preeclampsia and PTB.¹ It was shown to be safe with no effects on fetal growth, and no maternal or perinatal harm.¹ Studies with longer follow-up will further identify its treatment effects on the maternal and childhood outcomes.¹