March 10 (HealthDay News) -- Women who have migraines during pregnancy are 15 times more likely than other women to suffer a stroke, twice as likely to have heart disease and three times more likely to have blood clots and other vascular problems during pregnancy, says a U.S. study.

"Good prenatal care is essential. Women with persistent and severe migraine during pregnancy should be aware of their risk factors, such as high blood pressure, high cholesterol, diabetes, history of blood clots, heart disease and prior stroke," the study's lead investigator, Dr. Cheryl Bushnell, a neurologist at Wake Forest Baptist Medical Center, said in a Wake Forest news release. "There also seems to be a relationship between migraines and preeclampsia, one of the most common and dangerous complications of pregnancy."

The researchers also found that women 35 years and older were more likely to have migraines during pregnancy. Women age 40 and older were 2.4 times more likely to have migraines than women younger than 20, and white women were more likely to have them than women of any other race or ethnicity.

"Migraines, particularly those associated with an aura or visual changes around the time of the headache, have been previously linked to stroke and heart disease in women," Bushnell said. "This study further validates the association between the two."

For the study, she and her colleagues analyzed data from 33,956 pregnant women diagnosed with migraine. The findings were published in this week's issue of BMJ.

As many as 26 percent of women of childbearing age experience migraines.

"While some women experience relief from migraine headaches while pregnant, others have migraines that are more frequent and severe," Bushnell said. "The reasons these severe migraines are associated with stroke and vascular disease is not clear, but it may be that some women do not compensate as well for the increased vascular stresses of pregnancy, such as increased blood volume, stroke volume and heart rate."

"Regardless of the cause," she added, "active migraine during pregnancy should be viewed as a potential marker of vascular disease."

SOURCE: Wake Forest University Baptist Medical Center, news release, March 11, 2009; BMJ, news release, March 11, 2009