By Kathleen Doheny
WEDNESDAY, Feb. 17, 2016 (HealthDay News) -- Women who become pregnant at age 40 or older may face a greater risk of a "bleeding" stroke later in life, new research suggests.
"Women who have a pregnancy after the age of 40 appear to have a higher chance, 15 or 20 years down the line, of having a stroke, particularly the hemorrhagic type of stroke, which is bleeding in the brain," said lead researcher Dr. Adnan Qureshi. He is director of the Zeenat Qureshi Stroke Institute, in St. Cloud, Minn.
However, the study only uncovered an association between later pregnancies and potential stroke risk. It did not prove cause-and-effect.
Qureshi and colleagues reviewed data from more than 72,000 women, aged 50 to 79, enrolled in the Women's Health Initiative, a large-scale study launched to look at ways to prevent health problems in women.
The researchers zeroed in on more than 3,300 women who had a pregnancy after the age of 40. The investigators looked at their rates of stroke, heart attack and death from cardiovascular disease over the next 12 years, and then compared them with women who had a pregnancy at a younger age.
Hemorrhagic stroke was 60 percent more likely to occur in women who had a pregnancy after age 40, the study authors reported. The findings held even after taking into account age, race, the presence of congestive heart failure, high blood pressure and other factors that might boost stroke risk.
The risk of a stroke caused by a clot ("ischemic stroke"), a heart attack and death from cardiovascular disease also rose in those who were pregnant after age 40. However, after taking other factors into account, the increased risks for those events were no longer statistically significant, Qureshi added.
For all but the hemorrhagic strokes, risk factors such as high blood pressure explained the increased risk, Qureshi said. But pregnancy later in life seems to be a risk factor for hemorrhagic stroke by itself, he said.
Qureshi said he can't explain the possible link with certainty. It is known that women who become pregnant later in life have a higher risk of developing high blood pressure and diabetes during pregnancy. So, perhaps women who get pregnant later are predisposed to these problems, he suggested.
Or, "the pregnancy itself in later life may cause stress on the cardiovascular system," Qureshi added.
The link between later pregnancies and stroke risk is a new topic in the medical community, said Dr. David Liebeskind. He is director of the Neurovascular Imaging Research Core at the Ronald Reagan UCLA Medical Center in Los Angeles. However, "you would want to see confirmatory evidence" from additional studies, he said.
Liebeskind also reiterated that the researchers behind the new studies did not prove a cause-and-effect relationship between later pregnancies and stroke risk. "It doesn't mean that if you become pregnant above a certain age, you are going to have a hemorrhagic stroke," he said. "This is simply an association that has been found."
In future studies, researchers must "provide a rational basis for the underlying biology," Liebeskind said. "If it reaches that stage, perhaps there are underlying things that could be managed," he suggested. Or, ongoing research may identify a specific group of women who are vulnerable to stroke if they become pregnant after age 40.
Qureshi said that the finding suggests that women, when planning later-life pregnancies, should be aware of these risks. Once pregnant, they should be carefully monitored, as guidelines already recommend, he added.
"What the study suggests is, perhaps that rigorous monitoring should continue for years afterwards," Qureshi said.
The study findings are scheduled for presentation Wednesday at the American Stroke Association's annual meeting, in Los Angeles.
Studies presented at medical meetings are viewed as preliminary until published in a peer-reviewed journal.