An old joke says having a large family will make you lose your mind, but research suggests the opposite might be true.

Women who have more children may actually have a biological shield against strokes and vascular brain damage, according to a new study.

The findings, published recently in the Journal of the American Heart Association, highlight how a woman’s reproductive history — specifically how many live births she has had — can serve as a critical predictor for her long-term neurological health. 

Because women account for nearly 57% of all stroke deaths in the U.S., identifying specific risk factors is a top research priority.

Researchers analyzed data from 1,882 women participating in a project that has tracked the health of over 15,000 residents in Massachusetts since 1948.

At the start of the new study, the women were an average of 61 years old and had no history of a stroke.

Over an 18-year follow-up, they were monitored for clinical strokes as well as small areas of damage caused by restricted blood flow that can be seen on a brain MRI but might not cause immediate symptoms.

The results were striking. 

Women who had three or more live births were significantly less likely to suffer a stroke or have signs of vascular brain injury compared to those with fewer children. 

Specifically, when researchers accounted for other risk factors, women who had had three or more live births showed a 49% lower risk of stroke during the study period.

Why would more children lead to a healthier brain? The researchers point toward estrogen. 

During pregnancy, the body is exposed to high levels of its own natural estrogen.

“Our findings would suggest that reproductive factors — for example, number of live births — may be an additional factor to consider when assessing stroke risk in women,” said study co-author Dr. Sudha Seshadri, a neurologist at UT Health San Antonio.

While the study also looked at other factors like age at menopause and use of hormone replacement therapy, the number of live births was the most consistent predictor of a healthier brain.

“Inclusion of this risk factor in female-specific clinical prediction rules for stroke may enhance risk prediction in women,” Seshadri added in a news release.

By understanding these unique reproductive markers, doctors may soon be able to tailor stroke prevention plans specifically for women, ensuring those with lower natural estrogen exposure receive earlier interventions, researchers said.