Study finds increased risk of pregnancy-associated stroke among young women

Pregnancy was not found to raise the risk of stroke in older women, according to a study from Columbia University Medical Center and NewYork-Presbyterian. In younger women, however, the risk of stroke was significantly higher for those who were pregnant.

The researchers published their findings today in JAMA Neurology.

Pregnancy-associated stroke occurs in an estimated 34 out of 100,000 women. Previous studies suggested that the risk of pregnancy-associated stroke is higher in older women than in younger women.

"The incidence of pregnancy-associated strokes is rising, and that could be explained by the fact that more women are delaying childbearing until they are older, when the overall risk of stroke is higher," said Joshua Z. Willey, MD, assistant professor of neurology at CUMC, assistant attending neurologist on the stroke service at NewYork-Presbyterian/Columbia, and a senior author on the paper. "However, very few studies have compared the incidence of stroke in pregnant and non-pregnant women who are the same age."

In this study, the researchers examined data collected on every woman hospitalized for stroke in New York State between 2003 and 2012. Of these 19,146 women, age 12 to 55 years, 797 (4.2 percent) were pregnant or had just given birth.

The researchers found that the overall incidence of stroke during or soon after pregnancy increased with age (46.9 per 100,000 in women age 45 to 55 vs 14 per 100,000 in women age 12 to 24).

However, pregnant and postpartum women in the youngest group (age 12 to 24) had more than double the risk of stroke than non-pregnant women in the same age group (14 per 100,000 in pregnant women vs 6.4 in non-pregnant women).

For women age 25 to 34, pregnancy increased the risk 1.6 times. Stroke risk was similar in pregnant and non-pregnant women in the older age groups.

"We have been warning older women that pregnancy may increase their risk of stroke, but this study shows that their stroke risk appears similar to women of the same age who are not pregnant," said Eliza C. Miller, MD, a vascular neurology fellow in the Department of Neurology at CUMC and NewYork-Presbyterian and lead author of the study. "But in women under 35, pregnancy significantly increased the risk of stroke. In fact, 1 in 5 strokes in women from that age group were related to pregnancy. We need more research to better understand the causes of pregnancy-associated stroke, so that we can identify young women at the highest risk and prevent these devastating events."