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

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.

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.

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.

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.