Original Article|Articles in Press

Racial Disparities in Severe Maternal Morbidity in an Integrated Health Care System, Southern California, 2008–2017

Published:February 03, 2023DOI:



      The study’s objectives were to examine rates of severe maternal morbidity (SMM) over a 10-year period and assess racial/ethnic disparities in SMM among insured women in a large, integrated health care system in Southern California.


      We included Kaiser Permanente Southern California (KPSC) health plan members who gave birth at ≥20 weeks’ gestation in a KPSC-owned hospital during 2008–2017. An SMM case was defined as presence of one or more indicators of an SMM event during a birth hospitalization, identified using maternal electronic health records. Crude SMM rates/10,000 births were calculated by year and maternal race/ethnicity. Modified Poisson regression models were used to assess the association between race/ethnicity and SMM adjusted for other maternal demographics, pregnancy characteristics, and preexisting conditions.


      We identified 5,915 SMM cases among 335,310 births. Crude SMM rates increased from 94.7 per 10,000 in 2008 to 192.6 in 2015 and 249.5 in 2017. Non-Hispanic Black (adjusted risk ratio [aRR] 1.52; 95% confidence interval [CI] 1.37–1.69), Asian/Pacific Islander (aRR 1.29, 95% CI 1.18–1.41), and Hispanic (aRR 1.18, 95% CI 1.10–1.27) women had greater likelihood of SMM than non-Hispanic White women. After further adjusting for preexisting health conditions, differences in SMM by race/ethnicity remained.


      SMM rates increased during 2008–2017 and women of racial and ethnic minority groups, particularly non-Hispanic Black women, were more likely to experience an SMM event than non-Hispanic White women. Multilevel approaches to understanding structural and social factors that may be associated with racial and ethnic disparities in SMM are needed to develop and test effective interventions to reduce SMM.
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      Lisa P. Oakley, PhD, MPH, is an Epidemiologist at the Centers for Disease Control and Prevention. This work was conducted while she was serving as a CDC Epidemic Intelligence Service Officer in the Department of Research & Evaluation, Kaiser Permanente Southern California.


      Xia Li, MS, is a Biostatistician in the Department of Research & Evaluation, Kaiser Permanente Southern California.


      Sarah Y. Tartof, PhD, is an Infectious Disease Epidemiologist and Research Scientist in the Department of Research & Evaluation, Kaiser Permanente Southern California.


      Madeline Wilkes-Grundy, MD, is a Physician in the Department of Family Medicine at Kaiser Permanente West Los Angeles Medical Center and Faculty at Kaiser Permanente Bernard J. Tyson School of Medicine.


      Michael J. Fassett, MD, is a Physician and Director of Maternal-Fetal Medicine at Kaiser Permanente West Los Angeles Medical Center and Faculty at Kaiser Permanente Bernard J. Tyson School of Medicine.


      Jean M. Lawrence, ScD, MPH, MSSA, is the Senior Advisor for Diabetes Epidemiology and Program Director for Gestational Diabetes at the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH). She also participates in other maternal and women's health activities at NIDDK and NIH.