Over 28 million women in the US suffer from migraines, and when they happen in pregnancy previous research has suggested that this can increase the risk of maternal stroke. The study we just published in JAMA Neurology sought to determine the extent to which pre-existing blood pressure-related disorders increase this risk.

What did we do? We obtained data from the State of California for birth certifications and hospital discharge summaries for 3 million singleton, live births between 2007-2012. We examined these records for medical codes associated with migraines, strokes, and hypertensive disorders including high blood pressure and preeclampsia, a pregnancy complication characterized by high blood pressure, swelling, and protein in maternal urine. In our analysis, we adjusted for other factors that are commonly associated with stroke, such as age, maternal body mass index, race/ethnicity, maternal smoking, drug, and alcohol use, and maternal diabetes. Funding for the study was partly provided by the California Preterm Birth Initiative at the University of California San Francisco.

What did we find? We found that in 914 out of every 100,000 deliveries women suffered from migraines; in addition, strokes occurred in 29 out of every 100,000 deliveries. Compared to women without migraines, women with migraines during pregnancy were more likely to have a hypertensive disorder and to have a stroke during pregnancy or postpartum. In our analyses, hypertensive disorders explained 21% of the risk for stroke among women with migraines during pregnancy and delivery, and 27% of the risk for a postpartum stroke among women with migraines.

So what’s the take-away? Accordingly to the lead investigator on this study and our Center faculty member Dr. Gretchen Bandoli, PhD, MPH: “The findings suggest that by managing hypertension and preeclampsia in pregnancy, approximately one-quarter of the cases of stroke that can be attributed to migraines could potentially be prevented. Cardiologists should thus continue to counsel their pregnant patients on the importance of well-controlled blood pressure, particularly before and during pregnancy.”

However, she also cautioned that more research is needed: “Hypertension only accounted for one-quarter of the excess risk of maternal stroke associated with migraine, which indicates there are other risk factors that we have not yet quantified. Although maternal stroke is rare during pregnancy, delivery, and in the postpartum period, it can be deadly. We need more research to identify other factors contributing to stroke risk among women with migraines that can be modified to reduce the risk of a mom having a stroke.”

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