Duration of Medication Use for Opioid Use Disorder and Risk of Postpartum Overdose and Death.

Importance: Overdose is the leading cause of maternal mortality in the US, yet evidence on how medications for opioid use disorder (MOUD) affect postpartum overdose and mortality risk is limited. It is unclear whether cumulative MOUD exposure during this period reduces overdose or death beyond 90 days post partum. Objective: To examine whether longer duration of MOUD dispensed during pregnancy and early post partum is associated with reduced overdose or death through 365 days post partum. Design, Setting, and Participants: This is a retrospective cohort study of individuals delivering between 2007 and 2020, assessed through 1 year post partum or until the first outcome, through 2021. The study used Tennessee Medicaid (TennCare) data linked to vital records (birth and death certificates) and Tennessee Hospital Discharge Data. Participants were individuals aged 15 to 44 years with at least 1 day of dispensed MOUD during the exposure window (90 days before to 41 days after delivery), a delivery at least 20 weeks' gestation, and continuous TennCare enrollment during the exposure period. Data were analyzed from July 2024 to July 2026. Exposure: Total unique, nonoverlapping days of dispensed MOUD (buprenorphine and/or naltrexone) from 90 days before delivery through 41 days after delivery, with overlapping fills deduplicated so each calendar day was counted only once. Main Outcomes and Measures: The primary outcome was the first occurrence of all-cause death or overdose (opioid or nonopioid) from inpatient, outpatient, and emergency department claims 42 to 365 days post partum. Multivariable Cox proportional hazards models were used to estimate the association between MOUD days' supply and risk of death or overdose, adjusting for maternal and clinical characteristics. Results: The cohort included 9360 pregnancies among 7776 individuals (median [IQR] age at delivery, 27 [24-31] years). The 1-year postpartum risk of death or overdose was 1.58% (148 individuals), with a median (IQR) time to event of 186.5 (92.5-258.8) days. The median (IQR) MOUD duration during the 132-day exposure period was 88 (43-111) days. Longer MOUD duration was associated with lower risk of death or overdose, with the lowest hazard at 132 days' supply (adjusted hazard ratio for 132 vs 1 day, 0.52; 95% CI, 0.31-0.88). Conclusions and Relevance: Longer duration of MOUD receipt during pregnancy and early post partum was associated with lower risk of overdose or death in the first year post partum, underscoring the importance of supporting continuous MOUD treatment during this period.