It's long been known that certain complications of pregnancy can raise a woman's risk for heart trouble years later.

But new research shows that even the sisters of these women can be at higher heart risk — suggesting risks may be genetically shared within families.

“It may be important to identify [all of] these women early to offer preventive treatment for pregnancy complications as well as lifestyle counseling and follow-up for cardiovascular disease risk,” study lead author Ängla Mantel said. She's an associate professor in clinical epidemiology at the Karolinska Institute in Solna, Sweden.

Conditions such as premature delivery and preeclampsia — spikes in blood pressure — are common but dangerous complications of pregnancy. And numerous studies have shown that experiencing these issues places a woman at higher risk of heart disease later in life.

Mantel's team wondered what the role of genetics might be in this predisposition.

To find out, they looked at the medical records of more than 1.2 million Swedish women, all of who were free of heart disease when the study began.  

Most had never had any complication of pregnancy, but the study also included nearly 166,000 women who did have a history of such issues, as well as about 61,000 of their sisters who had never had pregnancy complications.

The team looked at medical records for a median 14 years, meaning half covered more years, half fewer.

Researchers found that, as expected, women with a history of pregnancy complications were at higher risk of long-term heart issues, compared to women without such histories. 

But when the researchers looked at the records of sisters of complication-affected women, they found a rise in risk there, as well. Compared to women who'd never had a complication of pregnancy, the "sisters group" also faced a 40% higher odds of heart issues over the follow-up period.

That finding shows "that the risk of cardiovascular disease after a pregnancy complication does not depend solely on the pregnancy itself, but can be influenced by genes and environmental factors,” Mantel said in a Karolinska news release. 

In other words, complications in pregnancy could signal added genetic heart risk for anyone related closely to the woman who experienced it.

The findings were published Feb. 7 in the European Heart Journal.