Elevated pre-pregnancy blood pressure may increase risk for miscarriage

Elevated blood pressure before pregnancy may increase the risk for miscarriage, according to new findings published April 2 in Hypertension. This proves true for women who exhibit high blood pressure preconception but have not been diagnosed with hypertension.

Researchers observed preconception blood pressure and reproductive outcomes in healthy women not diagnosed with high blood pressure or cardiovascular disease (CVD). The researchers noted this study does not indicate causation—elevated blood pressure may be associated with an increase in miscarriage; however, it does not necessarily cause miscarriage.

Results showed every 10-point increase in diastolic blood pressure was associated with an 18 percent increase in risk of pregnancy loss. Every 10-point increase in average arterial pressure was associated with a 17 percent increase in risk of pregnancy loss.

“Elevated blood pressure among young adults is associated with a higher risk of heart disease later in life, and this study suggests it may also have an effect on reproductive health,” said lead author Carrie J. Nobles, PhD, National Institute for Child Health and Human Development (NICHD) in Bethesda, Maryland and colleagues. 

Researchers studied 1,228 women who had experienced one to two pregnancy losses. The women used as part of the study cohort were currently trying to conceive and were also in a clinical trial to determine if consuming a low-dose of aspirin could reduce risk of miscarriage—though the clinical trial made no difference in the impact of blood pressure on pregnancy loss.

The women had their blood pressure measured when they were trying to conceive and then once again post-conception. The findings were similar for preconception and early-pregnancy blood pressure.

The average blood pressure pre-pregnancy was 111.6 mm Hg/72.5 mm Hg. The researchers noted 24 percent of the 797 women who conceived within six months, experienced a miscarriage.

There were some limitations in the study. Approximately 95 percent of the study cohort were white women. Additionally, the study cohort was comprised of women who already experienced a miscarriage, so it is unclear if the results could be generalized to all young women.