By AMERICAN HEART ASSOCIATION NEWS

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Women who have multiple pregnancies are at a greater risk of developing an irregular heart rhythm, and delivering a premature baby may be associated with cardiovascular disease, according to two new studies.

In the study that links the number of pregnancies to a type of irregular heartbeat called atrial fibrillation, researchers analyzed data from 34,639 participants in the Women’s Health Study. The participants had a median of two prior pregnancies and were healthy at the start of the study. After an average 20 years of follow-up, 1,532 AFib cases had occurred.

“We found that an increase in the number of pregnancies was associated with a higher risk of future atrial fibrillation,” said Jorge A. Wong, M.D., of McMaster University in Canada. “For example, women with four or more pregnancies were approximately 30 percent to 50 percent more likely to develop atrial fibrillation compared to women with no pregnancies.”

AFib can lead to blood clots, stroke, heart failure and other heart-related complications.

Repeated exposure to physiological, metabolic or hormonal factors during pregnancy may be the reason for the link, researchers said.

“The point here is not to discourage women from having children,” Wong said. “However, our research highlights that something about pregnancy predisposes women to this greater risk, and more research is needed to help us understand why.”

Women in the study were primarily of European descent, so the results may not apply to women of all ethnicities.

In a separate study, researchers at the Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital, both in Boston, reviewed data on 70,182 women in the Nurses’ Health Study II. They found that women giving birth for the first time who delivered a premature baby before 37 weeks had a 40 percent greater risk of later cardiovascular disease compared to women who delivered at term. Those who delivered before 32 weeks had double the risk compared to full-term deliveries.

“Ultimately, preterm delivery may be a useful prognostic tool to identify high-risk women early in life who would benefit from early screening, prevention and treatment,” the authors said.

The studies appear in the inaugural Go Red For Women issue of the American Heart Association journal Circulation.

Before the AHA awareness program launched in 2004, “little was known about the impact of pregnancy and its complications on subsequent cardiovascular disease in the offspring and mother,” said Joseph Hill, M.D., Ph.D., Circulation editor and a cardiologist at UT Southwestern Medical Center in Dallas.

“This inaugural issue is a new effort to address the menace of heart and vascular disease in women,” he said.