The Association Between Maternal–Fetal Medicine Physician Density and Pregnancy Outcomes

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.

Key Points

• An association between MFM physician density and maternal mortality is unclear.

• States with higher MFM density had a lower risk of maternal mortality than those with fewer.

• This study highlights the importance of increasing MFM access in underserved areas to potentially reduce maternal mortality.

Keywords

maternal death - maternal mortality - physician density - pregnancy-related mortality

• References

• 1 Hoyert DL. Health E-Stat: Maternal Mortality Rates in the United States, 2022. National Center for Health Statistics (U.S.); 2024.
• 2 Maternal mortality. Accessed October 31, 2024 at: https://www.who.int/news-room/fact-sheets/detail/maternal-mortality
• 3 Geller SE, Rosenberg D, Cox SM. et al. The continuum of maternal morbidity and mortality: factors associated with severity. Am J Obstet Gynecol 2004; 191 (03) 939-944
• 4 Rayburn WF, Perez JM, Xierali IM. Relocation of maternal-fetal medicine specialists in the United States. Am J Perinatol 2019; 36 (05) 526-529
• 5 Results and Data: Specialties Matching Service, 2024 Appointment Year. NRMP. February 13, 2024. Accessed October 31, 2024 at: https://www.nrmp.org/match-data/2024/02/results-and-data-specialties-matching-service-2024-appointment-year/
• 6 Sullivan SA, Hill EG, Newman RB, Menard MK. Maternal-fetal medicine specialist density is inversely associated with maternal mortality ratios. Am J Obstet Gynecol 2005; 193 (3 Pt 2): 1083-1088
• 7 CDC WONDER. Accessed October 31, 2024 at: https://wonder.cdc.gov/
• 8 Natality Information. Accessed December 9, 2023 at: https://wonder.cdc.gov/natality.html
• 9 Multiple Cause of Death Data on CDC WONDER. Accessed December 9, 2023 at: https://wonder.cdc.gov/mcd.html
• 10 Fetal Death Records - Online Database Help. Accessed October 31, 2024 at: https://wonder.cdc.gov/wonder/help/Fetal-Deaths.html
• 11 Catalano A, Davis NL, Petersen EE. et al. Pregnant? Validity of the pregnancy checkbox on death certificates in four states, and characteristics associated with pregnancy checkbox errors. Am J Obstet Gynecol 2020; 222 (03) 269.e1-269.e8
• 12 Indicator Metadata Registry Details. Accessed September 10, 2024 at: https://www.who.int/data/gho/indicator-metadata-registry/imr-details/4622
• 13 Joseph KS, Lisonkova S, Boutin A. et al. Maternal mortality in the United States: are the high and rising rates due to changes in obstetrical factors, maternal medical conditions, or maternal mortality surveillance?. Am J Obstet Gynecol 2024; 230 (04) 440.e1-440.e13
• 14 CDC. Pregnancy-Related Deaths: Data From Maternal Mortality Review Committees in 36 U.S. States, 2017–2019. Maternal Mortality Prevention. May 30, 2024. Accessed September 10, 2024 at: https://www.cdc.gov/maternal-mortality/php/data-research/mmrc-2017-2019.html
• 15 Donegan C. Geostan: an R package for Bayesian spatialanalysis. J Open Source Softw 2022; 7 (79) 4716
• 16 Donegan C, Chun Y, Griffith DA. Modeling community health with areal data: Bayesian inference with survey standard errors and spatial structure. Int J Environ Res Public Health 2021; 18 (13) 6856
• 17 Census Bureau Data. Accessed October 31, 2024 at: https://data.census.gov/
• 18 Maternal Mortality Rates in the United States. 2021 . March 16, 2023. Accessed October 30, 2024 at: https://www.cdc.gov/nchs/data/hestat/maternal-mortality/2021/maternal-mortality-rates-2021.htm
• 19 Ananth CV, Brandt JS, Hill J. et al. Historical and recent changes in maternal mortality due to hypertensive disorders in the United States, 1979 to 2018. Hypertension 2021; 78 (05) 1414-1422
• 20 Tavera G, Dongarwar D, Salemi JL. et al. Diabetes in pregnancy and risk of near-miss, maternal mortality and foetal outcomes in the USA: a retrospective cross-sectional analysis. J Public Health (Oxf) 2022; 44 (03) 549-557
• 21 Karlsen S, Say L, Souza JP. et al. The relationship between maternal education and mortality among women giving birth in health care institutions: analysis of the cross sectional WHO global survey on maternal and perinatal health. BMC Public Health 2011; 11 (01) 606
• 22 Girardi G, Longo M, Bremer AA. Social determinants of health in pregnant individuals from underrepresented, understudied, and underreported populations in the United States. Int J Equity Health 2023; 22 (01) 186
• 23 Hoffrage U, Lindsey S, Hertwig R, Gigerenzer G. Medicine. Communicating statistical information. Science 2000; 290 (5500) 2261-2262
• 24 Linden A. Conducting interrupted time-series analysis for single- and multiple-group comparisons. Stata J Promot Commun Stat Stata 2015; 15 (02) 480-500
• 25 Nelson DB, Moniz MH, Davis MM. Population-level factors associated with maternal mortality in the United States, 1997-2012. BMC Public Health 2018; 18 (01) 1007
• 26 Diab YH, Huang J, Nehme L, Saade G, Kawakita T. Temporal trend in maternal morbidity and comorbidity. Am J Perinatol 2024; 41 (13) 1867-1873
• 27 Joseph KS, Boutin A, Lisonkova S. et al. Maternal mortality in the United States: recent trends, current status, and future considerations. Obstet Gynecol 2021; 137 (05) 763-771
• 28 D'Alton ME, Friedman AM, Bernstein PS. et al. Putting the “M” back in maternal-fetal medicine: A 5-year report card on a collaborative effort to address maternal morbidity and mortality in the United States. Am J Obstet Gynecol 2019; 221 (04) 311-317.e1
• 29 Xierali IM, Nivet MA, Rayburn WF. Relocation of obstetrician-gynecologists in the United States, 2005-2015. Obstet Gynecol 2017; 129 (03) 543-550