According to the study’s lead author Elena Kuklina, a total of 4,085 pregnancy related stroke hospitalizations were documented in the United States in 1994-95, and that number rose 54 percent to 6,293 in 2006-07.

“We were alarmed,” Kuklina told AFP. “We expected to see some increase but we were surprised by the amount.”

Kuklina said one factor may be that more women are overweight when they become pregnant.

“Now, more and more women entering pregnancy already have some type of risk factor for stroke, such as obesity, chronic hypertension, diabetes or congenital heart disease,” she added.

“Since pregnancy by itself is a risk factor, if you have one of these other stroke risk factors, it doubles the risk.”