Treating mild hypertension in pregnancy is safe and beneficial, study shows

Robyn Horsager-Boehrer, M.D.
Obstetrics and Gynecology

Traditionally, Ob/Gyns have prescribed blood pressure medications only to patients with very high blood pressure – 160/90 or higher – to reduce risks such as maternal stroke or preterm delivery. Older data suggested that antihypertensive drugs might reduce blood flow to the uterus, causing fetal growth restriction.

But new research has shown that treating non-severe hypertension is safe for pregnant patients and their babies.

Chronic Hypertension and Pregnancy (CHAP), a randomized clinical study, demonstrated a 20% overall reduction of a composite measure of severe preeclampsia and related risks in patients who were actively managed to control mild hypertension, compared with a control group.

Importantly, adherence to the therapy was 86%. Women welcomed the opportunity to improve their health, and this gives me hope that more providers will be willing to prescribe antihypertensives during pregnancy.

Pregnancy itself taxes the cardiovascular system. Women who have been pregnant face a greater lifetime risk of heart problems than peers who haven’t. And patients with even mild hypertension in pregnancy are at increased risk of complications. Getting ahead of those risks could be key to better heart health later in life.

In April 2022, the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) announced their support of treating mild to moderate hypertension in pregnancy, with a starting point for treatment of 140/90 mm Hg.

CHAP showed immediate positive results – and time will tell whether treating mild to moderate hypertension can improve women’s lifelong cardiovascular health.

Inside the numbers: Data from the CHAP study

CHAP included 2,408 patients who enrolled in the trial before 23 weeks of pregnancy. Of these, 48% were non-Hispanic Black, 20% were Hispanic, and 28% were non-Hispanic white. All had elevated blood pressure readings between 140/90 and 160/105 (severe hypertension), and some had been previously diagnosed with high blood pressure.

During the trial, half the patients received standard prenatal hypertension care – monitoring for signs of preeclampsia (severe high blood pressure in pregnancy) such as persistent headache, shortness of breath, vision changes, or swelling in the hands and face. The other half received common blood pressure medication, such as labetalol or nifedipine.

Researchers compiled the data and found a composite risk reduction of 20% for:

• Fetal or newborn death
• Preterm delivery before 35 weeks of gestation
• Placental abruption – separation of the placenta from the uterine wall

There was no significant difference in fetal weight below the 10th percentile for gestational age: 11.2% in the control group and 10.4% in the medication group. CHAP showed that treatment of mild to moderate hypertension was safe and beneficial for pregnancy outcomes.

Optimizing blood pressure before or during pregnancy

For most women, blood pressure doesn’t rise during pregnancy. In fact, it falls gradually until around 20 weeks, then rises closer to baseline toward the end of pregnancy. Most patients should fall below 120/80 on average and start thinking about treatment at 140/90 or higher, according to ACOG.

If you start pregnancy with elevated blood pressure (130/80 or higher) you may have chronic hypertension that has not yet been diagnosed. So, it makes sense to discuss treatment options with your provider, working together to manage blood pressure early and reduce the risk of maternal or fetal complications.

In general, blood pressure medications are inexpensive and accessible under most types of health insurance. However, it sometimes takes a bit of time for new data to trickle into the clinical setting – and replace outdated information online.

If you know you have high blood pressure, talk with your doctor about whether taking antihypertensive medication is right for your pregnancy. If you are already on medications, plan to review those with your provider as there are some that are not appropriate to take during pregnancy. Don’t assume you should just stop taking the medication to avoid exposure to your unborn baby. It is your right to bring up any care you think could benefit your health.

The risk of pregnancy complications is never zero. But taking small steps to improve your health – such as managing your blood pressure – can make a big impact on your outcomes, potentially long after delivery.

To talk with a doctor about blood pressure management and pregnancy, call 214-645-8300 or request an appointment online.