Over a lifetime, women who've had a preterm delivery have a higher risk of heart disease, new research suggests.

The findings point to the fact that doctors should include a woman's reproductive history in assessments of heart disease risk, according to the researchers.

"Preterm delivery should now be recognized as an independent risk factor for IHD [ischemic heart disease] across the life course," said study co-leader Dr. Casey Crump, a professor of family medicine and community health at the Icahn School of Medicine at Mount Sinai in New York City.

Nearly 10% of babies born in the United States are delivered preterm (before 37 weeks of pregnancy).

For the new study, Crump and his colleagues analyzed data from millions of Swedish women who gave birth to a single baby and were followed for up to 43 years.

In the 10 years after giving birth, women who delivered preterm (34 to 36 weeks) had more than twice the risk of ischemic heart disease than those who delivered full-term, the study found. And women whose babies were delivered between 22 to 27 weeks had four times the risk, the study found.

Delivery between 37 and 38 weeks was associated with a 1.4-fold increased risk of heart disease.

Ischemic heart disease is a condition in which a buildup of plaque and clots in the arteries reduces blood flow to the heart.

While the risk of heart disease declined over time, it remained significantly higher for as long as 43 years after preterm delivery, researchers said.

The increased risk was independent of other contributors to heart disease, such as smoking or obesity, according to the study published June 29 in the Journal of the American College of Cardiology.

Crump said heart disease risk assessments should routinely include a woman's reproductive history, including preterm delivery and pregnancy complications.

"Women with a history of preterm delivery may warrant early preventive actions to reduce other IHD risk factors, including obesity, physical inactivity and smoking, and long-term monitoring for timely detection and treatment of IHD," Crump said in a journal news release.

Previous studies have shown that women who deliver preterm are more likely to develop high blood pressure, diabetes and high levels of fat in the blood—all of which are major risk factors for heart disease.