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Rates of maternal mortality in the United States are lower than previous estimates, according to a study published today in the American Journal of Obstetrics & Gynecology on March 13, 2024.

Researchers said inaccurate recordkeeping has created undue alarm that the number of women who die while pregnant or soon after giving birth is rising. The maternal mortality rate is stable, they report, and deaths due to obstetric complications have dropped.

"Obstetric complications as a cause of death have decreased over time. That is expected because we have improvements in medical care," said K.S. Joseph, MD, PhD, an obstetrician and gynecologist at the British Columbia Children's and Women's Hospital and Health Centre in Vancouver, Canada, and a coauthor of the new study.

This good news comes with sobering asterisks. The maternal mortality rate in this country is still the highest in the developed world, and Black women in the United States are far more likely to die during or after pregnancy than women in other racial or ethnic groups.

"Anytime we have disparities, it's always going to boil down to two things: Implicit bias and systemic racism," said Veronica Gillispie-Bell, MD, MAS, section head for obstetrics and gynecology at Ochsner Health in Kenner, Louisiana.

Gillispie-Bell said systemic racism results in economic insecurity and poor access to healthcare, spurring downstream harms like elevated maternal mortality among Black women. And implicit bias manifests as differential and potentially distressing treatment of Black women by physicians unaware they are doing so, she added.

Different Counting Method, Different Results

In 2003, officials of the National Center for Health Statistics (NCHS) recommended adding a "pregnancy checkbox" to US death certificates, to address undercounting of deaths that occurred because of a pregnancy complication. This checkbox identifies whether deceased women had been pregnant at the time of death, within 42 days of death, within 43 days to a year before death, not pregnant, or if this information is unknown.

The fact of being pregnant at death doesn't mean the pregnancy was to blame. But as Joseph and colleagues reported, NCHS guidelines count as a "maternal death" any death of a woman listed as pregnant on the certificate. From 2003 to 2017, this classification was true regardless of the person's age at death; since 2018, it has only been for women who died in childbearing years (age, 15-44). The NCHS made this change to reduce the number of deaths inaccurately attributed to pregnancy, Joseph said.

The checkbox method led to a purported 144% rise in maternal mortality in women aged 15-44, between 1999 and 2002 (9.65 of 100,000 live births) and 2018 and 2021 (23.6 of 100,000 live births).

Joseph and colleagues also looked for death certificates that mentioned an explicit cause of death, plus the fact of pregnancy. For these deaths to be linked to a pregnancy, they had to have been linked to an obstetric complication that occurred during pregnancy or by an underlying disease or condition the pregnancy worsened.

Using this refinement, the researchers identified 10.2 maternal deaths per 100,000 births from 1999 to 2002 and 10.4 maternal deaths per 100,000 births from 2018 to 2021. Deaths from direct obstetrical causes decreased. Indirect causes of maternal death such as cardiomyopathy, preexisting hypertension, or having a placenta that adhered to the uterine wall increased.

"The alternative method we used zeroes in on the real maternal deaths," Joseph said.

For Black women, the alternative method showed 25.7 deaths per 100,000 births from 1999 to 2002 and 23.8 deaths per 100,000 births from 2018 to 2021. Both figures are double the overall rates, and Black women were also more likely to experience conditions like hypertension and cardiomyopathy, according to the researchers.

Gillispie-Bell is the medical director of Louisiana's Pregnancy-Associated Mortality Review Board, which sifts through mortality records to glean accurate maternal mortality statistics for the state.

"The maternal mortality review committees are so important because we are going through and validating the data," Gillispie-Bell said. And that process also shows disparities in maternal mortality between Black women and other US women, Gillispie-Bell said.

One strategy to address the gap, which both Joseph and Gillispie-Bell supported, is to intensively treat all signs of hypertension and cardiomyopathy in pregnant Black women as soon as they appear. Gillispie-Bell also suggested that clinicians take the Implicit Association Test to learn if they are unwittingly bringing bias into their interactions with Black women, so they can shift their behavior if warranted.

"Our brains take shortcuts to process information," Gillispie-Bell said. "This is how biases happen. It's not anything for anybody to feel guilty about."

Joseph receives an investigator award from the BC Children's Hospital Research Institute. None for Gillispie-Bell.

Marcus A. Banks, MA, is a journalist based in New York City who covers health news with a focus on new cancer research. His work appears in Medscape, Cancer Today, The Scientist, Gastroenterology & Endoscopy News, Slate, TCTMD, and Spectrum.