Women who have a difficult time getting pregnant are at a higher risk of developing heart disease, a recent study suggests.
Researchers found women who were unable to become pregnant for at least five years, but eventually did, had a 19 percent increased risk of heart disease, compared with women who had no problems getting pregnant.
But whether such "subfertility," as it is called, is a risk factor for cardiovascular disease still remains unclear.
"We need to find out what it is about being subfertile that puts a women at excess risk of heart disease," said study co-author Dr. Nisha Parikh, a cardiologist from the University of Hawaii.
"That means looking at the causes of subfertility, and making sure that specific treatments aren't the cause of heart disease," Parikh said.
The study was published online in the journal Human Reproduction.
A long road to a pregnancy
Subfertility might be caused by thyroid disease, irregular menstrual periods and obesity, studies have shown. Polycystic ovarian syndrome, a hormonal imbalance that causes problems in egg development, is also known to play a role.
Previous studies suggest that women with polycystic ovarian syndrome appear to have higher rates of high cholesterol, high blood pressure and high blood sugar or diabetes, which are risk factors for heart disease.
"For a long time, we've wondered if conditions like polycystic syndrome may predispose women to cardiovascular risk," said Dr. C. Matthew Peterson, a fertility specialist at the University of Utah.
"We now have a study that documents heart disease-related events with subfertility," said Peterson, who was not involved with the research.
Parikh and colleagues studied nearly 863,000 Swedish women from 1983 to 2005. They examined whether subfertility was linked to heart disease-related events, such as being hospitalized or dying from a heart attack, stroke or heart failure.
Women were considered subfertile if they couldn't get pregnant for more than one year.
About 3,300 participants developed heart disease over the course of the study.
Overall, among those with no fertility problems, there were three cases of heart disease yearly per 10,000 women , whereas there were five cases per 10,000 women who were subfertile.
There was no increased risks for heart disease seen in subfertile women who became pregnant in four or less years, compared with women who had no trouble getting pregnant.
What the findings may mean
"The increased risk is actually small, but we still need to find out why there's a risk," Peterson said.
He also noted the study only focused on women, not men. "The actual risk for subfertility could have been higher," he said.
More than 7 million U.S. women of childbearing age have had trouble getting pregnant, [s1] according to a 2002 survey conducted by the Centers for Disease Control and Prevention (CDC).
But infertility isn't only a women's problem. About one-third of cases are due to men's infertility, reports the CDC.
Though the study showed an increase in risk, Parikh said she doesn't think women should be alarmed.
"This was an observational study," she said. "I don't think there's anything different that they should do."
Parikh advised women to go to their doctor and get regular checkups. "They should be concerned with heart disease like any other illness," she said.