Slightly high blood pressure before pregnancy tied to miscarriage risk

Women with slightly elevated blood pressure before they get pregnant may have an increased risk of miscarriage even when they’re not diagnosed with hypertension, a U.S. study suggests.

Researchers examined data on 1,228 women with at least one previous pregnancy loss who were trying to conceive. Out of the 797 participants who became pregnant during the study, 188, or about 24 percent, had a miscarriage. Even when their blood pressure was in a healthy range before pregnancy, each 10 mmHg (millimeters of mercury) increase in systolic blood pressure - the “top” number - was associated with an 8 percent higher risk of miscarriage, the study found. Each 10 mmHg increase in diastolic blood pressure - the “bottom” number - was associated with an 18 percent greater chance of miscarriage even when women didn’t have hypertension before conception.

 “Our study adds to evidence suggesting the importance of addressing high blood pressure among young women, both for their future cardiovascular health and potentially for their reproductive health as well,” lead study author Carrie Nobles of the Eunice Kennedy Shriver National Institute of Child Health and Human Development in Bethesda, Maryland, said by email. The American Heart Association defines hypertension, or high blood pressure, as a systolic reading of 130 mmHg or higher and diastolic readings of 80 mmHg or higher. Systolic pressure reflects the pressure blood exerts against artery walls when the heart beats. Diastolic pressure indicates the pressure when the heart rests between beats.

All women of reproductive age should take steps to keep their blood pressure at a healthy level, even if they’re not trying to conceive and don’t have a history of miscarriage, said Dr. Laura Benschop, a researcher at Erasmus Medical Center, Rotterdam, in the Netherlands who wasn’t involved in the study. “Previous studies (in women with hypertension) showed that a high blood pressure increases the risk for miscarriage,” Benschop said by email. “The current study examined women with normal blood pressure, and results show that women with a higher preconception or early pregnancy blood pressure, though within the normal range, are more at risk for a miscarriage.”