U.S.-born Black women at higher risk of preeclampsia than Black immigrants

Black women born in the United States have a higher risk of developing preeclampsia compared to Black women who immigrated to the country, according to preliminary research to be presented at the American Heart Association's Scientific Sessions 2020.

Preeclampsia, a serious complication of pregnancy characterized by high blood pressure and kidney dysfunction, is one of the leading causes of maternal death worldwide. It is 60% more common in Black women and is a risk factor for cardiovascular disease.

"Improving the cardiovascular health among U.S.-born Black women can make a difference in the trajectory of their pregnancies. Race itself is not the only contributing factor," said Garima Sharma, M.D., assistant professor of medicine at Johns Hopkins University School of Medicine in Baltimore and co-first author of the study.

In a review of data on nearly 4,000 Black women in Boston—born in and outside of the U.S. - researchers analyzed the role of their birthplace to their risk of preeclampsia and whether the length of time in the U.S. also affected the risk among the women who were not born in the country. The analysis included women from a subset of the Boston Birth Cohort—reviewing data on urban, low-income Black women in Boston. Race and ethnicity were self-reported. Of the study group, 1,652 were born in the U.S. and 2,302 were born in the Caribbean, Sub-Saharan Africa or other regions.

The study noted a higher prevalence of preeclampisa risk factors among U.S.-born Black women: smoking, diabetes, obesity, stress and previous pregnancies. They were also younger, less educated and more often single compared to foreign-born Black women.

The analysis found:

• foreign-born Black women had a 26% lower risk of preeclampsia, compared to native-born American black women; and
• when categorized by how long they lived in the U.S., immigrants who had lived in the U.S. for less than 10 years had an 8.5% risk of preeclampsia, compared to a 9.3% risk for those who had lived in the U.S. more than 10 years.

"Our findings suggest the 'healthy immigrant effect' tends to wane the longer an immigrant lives in the U.S.," Sharma said. The healthy immigrant effect refers to the fact that immigrants are typically healthier when they arrive in the U.S.

"The fact that the prevalence of preeclampsia in the mothers who were not born in the U.S. increased over time and grew closer to matching the risk of the U.S.-born mothers stresses the importance of improving cardiovascular health," she said. "We know that preeclampsia is associated with increased cardiovascular risk in later life, due mostly to the same risk factors.

Future research should focus on why and what we can do to implement changes to prevent cardiovascular disease and improve heart health among Black women."