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High blood pressure before pregnancy linked to heightened miscarriage risk

Every 10 mmHg rise in diastolic blood pressure seems to boost risk

Caroline White

Wednesday, 04 April 2018

Women whose blood pressure is high before they conceive might be at a heightened risk of miscarriage, suggest the findings of a study* published in the journal Hypertension.

The researchers found that every 10 mmHg rise in diastolic blood pressure was associated with an 18 per cent higher risk of miscarriage, while the same increase in mean arterial pressure was associated with a heightened miscarriage risk of 17 per cent.

The researchers drew on data collected as part of the Effects of aspirin in gestation and reproduction (EAGeR) trial, which aimed to find out if daily low-dose aspirin (81mg) could prevent miscarriage in women who had a history of miscarriage.

The EAGeR trial included more than 1200 women between the ages of 18 and 40 and took blood pressure readings before they became pregnant and again in their fourth week of pregnancy.

Average diastolic blood pressure was 72.5mmHg; normal blood pressure in adults is a diastolic reading of below 80mmHg. The researchers noted an increase in miscarriage among women who had a diastolic reading above 80 mmHg, which was the case for around one in four of the study participants.

Blood pressure before conception was not related to ability to become pregnant or to having a live-born child after taking account of potentially influential factors.

This is an observational study and the researchers note that while the study cannot prove whether high blood pressure causes the loss of a pregnancy, another, yet-to-be identified factor might account for their findings.

However, the association between blood pressure before conception and pregnancy loss remained the same when they took account of other factors that could heighten the risk such as increasing age, higher body mass index, or smoking, history of previous pregnancies and any associated miscarriages.

Lead study author Enrique Schisterman commented: “Our findings suggest that attaining a healthy blood pressure before pregnancy could not only have benefits later in life, but also reduce the chances for pregnancy loss.”

Co-author and postdoctoral fellow Carrie Nobles said that further research might help clarify whether treating high blood pressure and other health risk factors before conception could improve pregnancy outcomes.

*Preconception Blood Pressure Levels and Reproductive Outcomes in a Prospective Cohort of Women Attempting Pregnancy. Hypertension 2018:DOI: 10.1161/HYPERTENSIONAHA.117.10705

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