The number of US women who died within a year after pregnancy more than doubled between 1999 and 2019, with the highest deaths among Black women, researchers said on Monday.
There were an estimated 1,210 maternal deaths in 2019, compared with 505 in 1999, according to a study published in the medical journal JAMA.
The greatest increases over time were seen among American Indian and Alaska Native women, the researchers said.
The number of deaths per 100,000 live births rose from 12.7 to 32.2 overall, from 14.0 to 49.2 among American Indians and Alaska Natives, 26.7 to 55.4 among Blacks, 9.6 to 20.9 among Asians, Native Hawaiians and Other Pacific Islanders, 9.6 to 19.1 among Hispanics, and 9.4 to 26.3 among whites, they estimated.
Unlike previous US studies of maternal mortality, which focused on national trends, the current study analyzed data state-by-state.
To the researchers' surprise, Black women had the highest maternal mortality rates in some Northeast states.
"Often, states in the South are called out as having the worst maternal mortality rates in the nation, whereas California and Massachusetts have the best. But that doesn't tell the whole story," study leader Dr. Allison Bryant of Mass General Brigham in Boston said in a statement. "It's essential to look at the disparities between populations that exist even in the 'best' states."
Southern states had high maternal mortality across all race and ethnicity groups, but especially for Black individuals, while Midwest and Great Plains states had the highest rates for American Indian and Alaskan Native women.
The most common causes of death within one year after the end of pregnancy include mental health conditions, excessive bleeding, cardiac and coronary conditions, infections, blood clots, and pregnancy-related high blood pressure, according to the US Centers for Disease Control and Prevention.
"Our findings provide important insights on maternal mortality rates leading up to the pandemic, and it's likely that we'll see a continued increase in the risk of maternal mortality across all populations if we analyze data from subsequent years," Bryant said.
"Black individuals would likely still have the highest rate, but there may be a higher uptick in some of the other groups in the last few years."