ORCID

0000-0003-2438-1699 (Kawakita), 0009-0009-2851-7574 (Atwani), 0009-0008-3130-5233 (Hayasaka), 0000-0003-3334-1437 (Robbins), 0000-0001-7925-5302 (Saade)

Document Type

Article

Publication Date

2025

DOI

10.1055/a-2717-3951

Publication Title

American Journal of Perinatology

Volume

Advance online publication

Pages

6 pp.

Conference Name

45th Annual Meeting- the pregnancy meeting of the Society for Maternal-Fetal Medicine, Jan. 27-Feb. 1, Denver, Colorado

Abstract

Objective

We sought to examine the association between maternal-fetal medicine (MFM) physician density and adverse pregnancy outcomes at the state level.

Study Design

This was a cross-sectional analysis of publicly available, state-level data from 2018 to 2021, including Natality, Multiple Cause-of-Death, and Fetal Death databases. The number of active MFM physicians per year was obtained for each state from the American Medical Association Masterfile. The primary exposure was the density of MFM per state, categorized into three groups: (1) low density (< 30 MFM physicians per 100,000 live births), (2) moderate density (30-59 MFM physicians per 100,000 live births), and (3) high density (≥60 MFM physicians per 100,000 live births). Our primary outcome was maternal mortality during pregnancy and up to 42 days postdelivery. Our secondary outcomes were pregnancy-related mortality up to 365 days postdelivery and stillbirth. We calculated adjusted incident rate ratios (aIRR) and average marginal effect (AME) with 95% confidence intervals (95% CI) using multivariable negative binomial mixed effects regression models.

Results

Overall, there were 14,792,743 live births, 3,440 maternal mortalities, 4,980 pregnancy-related mortalities, and 90,848 stillbirths included. The median MFM density across states was 31.6 per 100,000 live births (interquartile range: 21.9-42.5). States with high MFM density had a reduced risk of maternal mortality (aIRR: 0.70; 95% CI: 0.58-0.85) and pregnancy-related mortality (aIRR: 0.83; 95% CI: 0.71-0.98) compared with states with low MFM density, corresponding to 7.29 (AME: 95% CI: 3.58-11.00) and 5.57 (AME: 95% CI: 0.74-10.40) less mortality per 100,000 live births, respectively. States with moderate MFM density had a similar risk of maternal mortality compared with low MFM density states (aIRR: 1.02; 95% CI: 0.87-1.20).

Conclusion

High MFM-density states have a decreased risk of maternal mortality compared with low MFM-density states, suggesting a critical role of MFM in reducing maternal mortality.

Rights

© 2025. The Authors.

This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited.

Original Publication Citation

Kawakita, T., Atwani, R., Hayasaka, M., Robbins, L., & Saade, G. (2025). The association between maternal-fetal medicine physician density and pregnancy outcomes. American Journal of Perinatology. Advance online publication. https://doi.org/10.1055/a-2717-3951

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