Changes in Age Distribution and Maternal Mortality in a Subset of the US, 2014-2021.

INTRODUCTION: This study aimed to determine the association between changes in age distribution and maternal mortality rates (MMR) in a subset of the United States between 2014 and 2021.

METHODS: A serial cross-sectional analysis of birthing individuals aged 15-44 years from 2014 to 2021 was performed. States that had not adopted the pregnancy checkbox as of 2014 were excluded from the primary analysis. A significant inflection point in MMR was identified in 2019 with the Joinpoint Regression Program, so all analyses were stratified: 2014-2019 and 2019-2021. The Kitagawa decomposition was applied to quantify the contribution from (1) changes in age distribution and (2) changes in age-specific MMR (ASMR) to total MMR. Data analysis occurred between 2022 and 2023.

RESULTS: From 2014 to 2021, the mean (standard deviation) age of birthing individuals changed from 28.3 (5.8) to 29.4 (5.7) years. The MMR (95% CI) increased significantly from 16.5 (15.8-18.5) to 18.9 (17.4-20.5) per 100,000 live births from 2014 to 2019 with acceleration in MMR to 31.8 (30.0-33.8) by 2021. The change in maternal age distribution contributed to 36% of the total change in the MMR from 2014 to 2019 and 4% from 2019 to 2021. Age-specific MMR components increased significantly for those aged 25-29 years and 30-34 years from 2014 to 2019. All 5-year age strata except the 15-19 year old group saw increases in age-specific MMR from 2019 to 2021.

CONCLUSIONS: MMR increased significantly from 2014 to 2021 with rapid increase after 2019. However, older age of birthing individuals explained only a minority of the increased MMR in both periods. The greatest contribution to MMR arose from increases in age-specific MMR.