Pregnant women with mild high blood pressure benefit from treatment

Pregnant women with mild high blood pressure and their babies can benefit from treatment, according to a large study co-authored by a researcher at the University of Wisconsin School of Medicine and Public Health.

Current national guidelines only suggest treating pregnant women with severe high blood pressure, but that could change following the new study, which was published Saturday in the New England Journal of Medicine. 

Guidelines are set by the American College of Obstetricians and Gynecologists.

Until the new study, there had been some concern that taking blood pressure medication while pregnant might increase the risk that babies would be born small for their gestational age.

However researchers studying 2,400 pregnant women around the country found no significant difference in size between babies born to mothers who were treated for their mild high blood pressure, and those born to mothers who went untreated.

Moreover, the women who received treatment were less likely than the untreated women to develop serious conditions such as severe preeclampsia, preterm birth and death of the fetus. Preeclampsia involves high blood pressure and can lead to serious, even fatal complications for both mothers and babies.

“This might be an opportunity to reduce hypertension-related complications for the mom and the baby,” said Kara Hoppe, an associate professor of obstetrics and gynecology at UW and one of the co-authors of the study.

Hoppe added that one bad outcome is prevented with every 14 pregnant women who receive treatment for their blood pressure. 

The women in the study all had chronic, but not severe, high blood pressure. Some of the women were treated for their high blood pressure with medications such as labetalol and nifedipine; the other women received no blood pressure treatment.

Of the untreated women, 37% experienced preeclampsia and other complications; only 30% of the treated women experienced the complications.

Of the untreated women, 16.7% delivered their babies early, before 35 weeks; only 12.2% of the treated group delivered before 35 weeks.

To be included in the trial, women had to have blood pressure in the range from 160/110 down to 140/90. The top number in these readings measures the blood pressure in the arteries each time the heart beats. The bottom number measures the blood pressure as the heart relaxes between beats.

Women enrolled in the trial between 20 to 23 weeks into their pregnancy and were followed until two weeks after the delivery of the baby.

The study was conducted at 70 academic medical centers, including UW Health and the Medical College of Wisconsin.