Traditional Versus Contemporary Models for Identifying Causes of Maternal Death: A Population-Based Study.

Objective: To examine differences in cause-of-maternal-death assignment based on underlying versus multiple causes of death.

Design: Cross-sectional, population-based study.

Setting: United States, 1999-2002 and 2018-2022.

Population: 1633 maternal deaths in 1999-2002 and 1929 maternal deaths in 2018-2022.

Methods: Causes of death were identified based on the underlying cause of death and also based on multiple causes of death. The frequency of six selected obstetrical causes of death was quantified and ranked.

Results: Pre-eclampsia (0.87 per 100 000 live births, 95% confidence interval [CI] 0.74-1.02) was the most common cause of maternal death in 2018-2022, when cause-of-death assignment was based on the underlying cause of death. Amniotic fluid embolism and cardiomyopathy tied for second rank, haemorrhage placed fourth and puerperal sepsis and uterine rupture tied for the fifth rank. Rankings based on multiple causes of death showed a different pattern: haemorrhage (1.13 per 100 000 live births, 95% CI 0.98-1.29) was the most common cause, followed by pre-eclampsia, cardiomyopathy, amniotic fluid embolism, puerperal sepsis and uterine rupture. There was no significant correlation between the cause-of-maternal death rankings based on the underlying and multiple causes of death (correlation coefficient 0.62, 95% CI-0.39, 0.95; p value 0.19) in 2018-2022. Cause-of-death rankings were significantly correlated under the two methods of cause-of-death assignment in 1999-2002 (correlation coefficient 0.83, 95% CI 0.05, 0.98; p value 0.04).

Conclusion: Basing cause-of-death assignment and ranking of the causes of maternal death using a multiple causes-of-death approach may better inform clinical and public health priorities for reducing maternal mortality.