Research shows racial-ethnic differences in the risk of pregnancy-related high blood pressure

The risk of pregnancy-related high blood pressure varied markedly among subgroups of Asian American, Native Hawaiian and Pacific Islander people, highlighting the need for tailored prevention and treatment, according to research published today in the Journal of the American Heart Association, an open access, peer-reviewed journal of the American Heart Association.

"There are known ways to help prevent and treat high blood pressure during pregnancy. Our findings can help health care professionals identify those who are at higher risk," said study lead author Jennifer Soh, M.S., who was a master's student in Community Health and Prevention Research Program at Stanford University School of Medicine when she conducted the study. "Early identification and treatment can help prevent serious, downstream complications for both the pregnant individuals and their infants."

Pregnancy-related high blood pressure increases the risk of heart attack and stroke and is one of the leading causes of maternal illness and death, according to the U.S. Centers for Disease Control and Prevention. In the United States, about 1 in 7 pregnancies are affected by a high blood pressure-related condition during pregnancy. These conditions can be managed and treated with medication or lifestyle changes, according to the  American Heart Association.

Previous research has indicated that the risk of developing pregnancy-related high blood pressure differs among people of different races and ethnicities due to social determinants of health. Yet little is known about differences in risk between Asian American, Native Hawaiian and Pacific Islander populations as they are often studied together, despite the diversity found within these groups.

To understand the risk by race and ethnicity, researchers in this study analyzed the risks of five hypertensive disorders of pregnancy in individuals of Asian American, Native Hawaiian and Pacific Islander descent. The conditions included chronic hypertension, gestational hypertension (high blood pressure during pregnancy), preeclampsia, eclampsia and chronic hypertension with preeclampsia. Preeclampsia is high blood pressure during pregnancy characterized by too much protein in the urine or other signs of organ damage. Eclampsia is a serious complication of preeclampsia that can cause seizures.

The analysis found:

• The lowest frequency of pregnancy-related high blood pressure was found in the Chinese subgroup at 3.7%, while the Guamanian subgroup had the highest frequency at 13%.
• Using the Chinese population as the reference point, the risk of the pregnancy-related high blood pressure conditions was elevated (two- to three-times higher) among Filipino and Pacific Islander populations: Hawaiian, Guamanian, Samoan and other Pacific Islander individuals, after adjusting for a variety of sociodemographic and maternal-health related factors.
• Only Japanese, Korean and Vietnamese individuals tended to have risks that were not elevated compared to the Chinese reference group.

The observed racial-ethnic differences in risk highlight the variation in lived experiences of the individuals included in this study. Future studies should examine more structural and social factors that could help explain the differences in the elevated risks found in this study."

Jennifer Soh, M.S., lead author

The study had several limitations. It relied on medical diagnostic codes, which may be subject to underreporting or misclassification; the data only included individuals in California, so the results may not apply to other people living in different communities; and the study could not account for the effects of the COVID-19 pandemic, since the pandemic began after the study period. Finally, the study could not consider additional potential, yet important, factors that may impact high blood pressure during pregnancy, such as air pollution, neighborhood walkability and food access.

Study details, background and design:

• Researchers reviewed records from 2007-2019 from the California Department of Health Care Access and Information for 772,688 pregnant individuals who self-reported that they were of Asian American, Native Hawaiian and Pacific Islander descent, and they were divided into 15 subgroups: Chinese, Japanese, Korean, Vietnamese, Cambodian, Thai, Laotian, Hmong, Indian, Filipino, Other Asian, Hawaiian, Guamanian, Samoan and Other Pacific Islander.
• The average age of individuals included in the study was 32 years.
• Researchers reviewed infant and fetal birth and death certificates linked to maternal hospital discharge records for each of the five hypertensive disorders of pregnancy.
• The researchers used statistical tools to determine the relative risks of the hypertensive disorders of pregnancy within each subgroup.