A complicated pregnancy may increase a woman's risk of dying from heart disease later in life, new research suggests.
The risk is particularly high for women who've had more than one health problem during pregnancy, said senior study author Barbara Cohn, director of child health and development studies at the Public Health Institute in Berkeley, Calif.
"We discovered there were some combinations of pregnancy complications that were associated with as much as a sevenfold increase in the risk of cardiovascular disease death," Cohn said.
For example, the risk of fatal heart disease prior to age 60 doubled or even tripled in women who developed pre-eclampsia, a sudden increase in blood pressure late in pregnancy. But a woman's risk escalated six times if she developed pre-eclampsia on top of high blood pressure she already had earlier in her pregnancy, the researchers found.
However, the new study could only show associations between pregnancy complications and later heart problems; it did not prove a cause-and-effect relationship.
The findings were published online Sept. 21 in Circulation, the journal of the American Heart Association.
Heart disease is the number-one killer of American women, according to the American Heart Association.
In this study, researchers analyzed decades of data gathered from about 15,000 women who became pregnant in the Oakland, Calif., metropolitan area between 1959 and 1967. Overall, 64 percent of the mothers had no complications, 31 percent experienced a single complication, and 5 percent had two or more complications.
The most common complication was gestational high blood pressure, followed by preterm delivery, low-birth-weight delivery, and hemoglobin decline (a problem with red blood cells).
As of 2011, 368 women in the study had died of heart disease. The researchers compared the women's heart health history to the complications they experienced during pregnancy, to see whether any complications provide a warning of future heart problems.
Additional dangerous combinations found in the study included:
•A seven times higher risk for mothers with pre-existing high blood pressure and a preterm delivery.
•A five times greater risk for women with pre-existing high blood pressure and delivery of a low-birth-weight baby.
•A five times higher risk for mothers with high blood pressure that developed as a result of pregnancy, and a preterm delivery.
The researchers also reported an unexpected result -- gestational high blood pressure was associated with heart disease death only in black women. Black women made up 22 percent of the study population. And, the study found black women were 1.7 times more likely to die from heart problems, while white, Asian and Hispanic women had no increased risk due to gestational high blood pressure.
The researchers also identified two new pregnancy complications that may increase a woman's risk of heart disease death. High levels of sugar in a woman's urine were associated with a four times increased risk of later heart disease death, when compared to women who experienced normal pregnancy.
And, women were almost twice as likely to die from heart disease if they had an abnormal decline in their levels of hemoglobin, which is the protein in red blood cells that delivers oxygen throughout the body, the investigators found.
High levels of sugar could indicate that a woman is experiencing diabetes during pregnancy, and diabetes is a risk factor for heart disease, Cohn said. Low hemoglobin levels could lead to increased stress on the heart, since it must pump faster to supply oxygen to the body, she suggested.
Obstetricians and family doctors should use these "warning signs" to identify women who carry a heavier risk of heart attack, stroke and heart failure, Cohn said. These women can be counseled to follow a heart-healthy lifestyle, and possibly be given treatment to help control high blood pressure or other heart risk factors.
"Pregnancy really is a stress test for the cardiovascular system. If these physicians could take note of whether their patients had some of these complications, they might be able to intervene early," she said. "It's a low-cost way of finding women who might be able to benefit from the dramatic advances in cardiovascular medicine that have occurred over the last few decades."
Dr. Rita Redberg, a professor and director of women's cardiovascular services at the University of California, San Francisco, said these findings present a great opportunity to identify women at a young age who are more likely to die of heart disease.
"Obviously, we're catching women younger when we're doing it during pregnancy," Redberg said. "While it's never too late, we like to start young."
Young mothers might be more motivated to take their doctor's advice about a heart-healthy lifestyle, Redberg added.
"These are women now who have young children and are thinking how they need to be healthy and stay around for their kids," she said. "It's an opportune time to teach them how to reduce their risk factors."
