Severe Maternal Morbidity Among Pregnant People With Opioid Use Disorder Enrolled in Medicaid.

Importance: Pregnant people with opioid use disorder (OUD) are at high risk for potentially avoidable maternal morbidity. The majority of pregnant people with OUD receive health insurance through state Medicaid programs, but there is little comprehensive data on the burden of severe maternal morbidity (SMM)-a composite measure of adverse maternal health outcomes-among this high-risk group. Objective: To estimate rates of SMM among Medicaid-enrolled pregnant people with OUD from 2016 to 2018. Design, Setting, and Participants: Using the Transformed Medicaid Statistical Information System Analytic Files, this cross-sectional study identified 96 309 pregnant people with OUD enrolled in Medicaid in 47 states with 108 975 deliveries between March 1, 2016, and November 16, 2018. Data were analyzed from August 1, 2023, to September 1, 2024. Main Outcome and Measures: SMM was identified using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision diagnosis and procedure codes for 20 relevant conditions and was measured per 10 000 live births nationally and by state. Rates of SMM were also stratified by the timing of Medicaid enrollment before delivery. Results: From 2016 to 2018, 96 309 Medicaid enrollees had a diagnosis of OUD before a live birth (108 975 deliveries). The mean (SD) age of Medicaid-enrolled pregnant people with OUD was 28.8 (5.0) years. The mean (SD) rate of OUD among pregnant people enrolled in Medicaid was 324.8 (260.9) per 10 000 live births across states. Among this group, the mean (SD) unadjusted rate of SMM excluding blood transfusions among those with OUD was 292.1 (112.3) per 10 000 live births, with these rates varying substantially across states, from 101.0 per 10 000 live births in South Dakota to 682.2 per 10 000 live births in California. Adjustment for enrollee characteristics and comorbidities did not meaningfully alter the estimated rate of SMM (305.6 [95% CI, 245.2-408.2] per 10 000 live births). Rates of SMM generally increased with decreased durations of Medicaid enrollment. Conclusions and Relevance: This cross-sectional study of pregnant people enrolled in Medicaid found that the rate of OUD among this group was more than twice as high as previous estimates. Pregnant people with OUD face a disproportionately high risk of SMM, particularly those who enroll in Medicaid later in pregnancy. Targeted interventions that facilitate early Medicaid enrollment and coverage continuity may be needed to reduce the burden of adverse outcomes in this group.