A new study led by the University of British Columbia in Canada has discovered the method used by the United States Centers for Disease Control and Prevention (CDC) to measure maternal death rates may be significantly overestimating their results.
The National Vital Statistics System of the CDC has estimated that maternal death rates in the United States have more than tripled over the course of the 21st century, with 32.9 deaths per 100,0000 live births in 2021.
Maternal deaths are described as those that occur during pregnancy, childbirth, or postpartum as a result of pregnancy or childbirth. However, the study authors believe the CDC’s methodology for calculating maternal death rates is including all deaths than happen to pregnant women, even when they are not related to pregnancy or childbirth.
“If you’re pregnant and die in a car crash, that’s not a maternal death,” said senior author, Cande Ananth, chief of epidemiology and biostatistics in the Robert Wood Johnson Medical School at Rutgers University in New Jersey. “A big change driving recent increases in the official numbers stems from the tendency to include more and more cancers unrelated to pregnancy in maternal death rates. A woman who had a diagnosis of breast cancer before conception and then died after the pregnancy ended or – a woman who would have died if she’d never gotten pregnant – will be counted as a maternal death.”
In their analysis, the researchers first calculated maternal deaths using the CDC’s methodology and then again, restricting maternal deaths to those where “pregnancy” appeared at least once amid the causes of death on the death certificate. The CDC method found maternal death rates of 9.65 deaths per 100,000 live births in 1999 to 2022 and 23.6 deaths in the 2018 to 2021 time period. Using their own methodology, the researchers found similar results for the 1999 to 2002 period, with 10.2 deaths per 100,000 live births. However, the results for the 2018 to 2021 era showed a very small increase to 10.4 deaths per 100,000 live births.
“Our study, which identified maternal deaths using a pragmatic definition-based methodology, showed stable rates of maternal mortality and a reduction in deaths from obstetrical complications,” said K. S. Joseph, lead author of the new study and a professor of obstetrics and gynecology at the University of British Columbia, Canada. “Moreover, the analysis by cause-of-death provides evidence that can enable focused prevention initiatives targeted at high-risk and vulnerable subpopulations.”