Women whose blood pressure is high before they are pregnant may be at increased risk for miscarriage, a new study has found.

Researchers used data from a study of 1,228 women attempting pregnancy after having previously lost a baby. Of the 797 who achieved pregnancy, 188, or almost a quarter, lost the baby again.

The study, in Hypertension, found no association of blood pressure with the ability to get pregnant. But after adjusting for smoking, body mass index, marital status, education, race and other factors, they found that for each 10-point increase in pre-pregnancy diastolic blood pressure — the bottom number in a blood pressure reading — there was a 17 percent increase in the risk of pregnancy loss.

There are many reasons for miscarriage, and often the cause is unknown. But inflammation and blood vessel impairment, which are characteristic of hypertension, are also known to be involved in pregnancy loss.