Have US maternal mortality rates actually doubled?

March 15, 2024 - Research suggests that the rising rates of maternal mortality in the United States may represent changes in maternal mortality surveillance instead of an increase in incidence. While data from the National Vital Statistics System (NVSS) suggests a 144% increase in maternal mortality from 1999 to 2021, an American Journal of Obstetrics and Gynecology analysis suggests more modest increases.

The study, published on March 12, 2024, attempted to understand whether the changes in US maternal mortality were linked to changes in obstetrical factors, maternal medical conditions, or maternal mortality surveillance.

Based on NVSS reports, there were 32.9 maternal deaths per 100,000 live births in 2021, a significant increase from the 2018 rate of 17.4 maternal deaths per 100,000 live births.

While this may seem like a significant rise, researchers theorized that the changes in incidence could be linked, in part, to the introduction of the pregnancy checkbox to death certificates in 2003. The American Journal of Obstetrics and Gynecology notes that this component was launched to improve “maternal death ascertainment.”

However, the introduction of this box resulted in some significant errors, as many women well past reproductive age were marked as pregnant at their time of death. Additional restrictions were enforced to minimize this risk. However, the NVSS and the National Center for Health Statistics (NCHS) still consider maternal deaths as “deaths in pregnancy or in the postpartum period, including deaths identified solely because of a positive pregnancy checkbox on the death certificate among women aged 15 to 44 years.”

To assess how the methodology impacted maternal mortality rates, the investigators analyzed maternal deaths using the NVSS and NCHS methods and an alternative method that restricted maternal deaths to incidences that mentioned pregnancy among causes of death on the death certificate.

Based on the NVSS and NCHS methods, maternal mortality rates increased from 9.65 to 23.6 per 100,000 live births from the 1999–2002 to 2018–2021 period. However, the alternative method only indicated a minor increase in maternal mortality rates from 10.2 to 10.4 deaths per 100,000 live births from the 1999–2002 to 2018–2021 period.

Researchers concluded, “The high and rising rates of maternal mortality in the United States are a consequence of changes in maternal mortality surveillance, with reliance on the pregnancy checkbox leading to an increase in misclassified maternal deaths. Identifying maternal deaths by requiring mention of pregnancy among the multiple causes of death shows lower, stable maternal mortality rates and declines in maternal deaths from direct obstetrical causes.”