Trends in prenatal opioid use disorder in California, 2010-2022.

Introduction: Opioid-related deaths among perinatal populations have increased sharply in the United States. Whether the recent ascendence of illicit fentanyl and other synthetic opioids in the drug supply translates to increasing prenatal opioid use disorder (OUD) remains unknown. This study tested whether California's comparatively late fentanyl influx, in 2019, was associated with a subsequent increase in OUD among pregnant people.

Methods: This ecologic, repeated retrospective cohort study examined annual cohorts of individuals with an index live-birth delivery in California, 2010-2022. Analyses used statewide, all-payer linked hospitalization and emergency department (ED) records. Overall and subgroup-specific trends in prevalence of prenatal OUD, assessed using ICD-9/10-CM diagnoses recorded at delivery hospitalization and during prenatal ED visits, were examined using joinpoint and logistic regression analyses. Data analysis was conducted in 2025.

Results: The study included 4,381,064 index deliveries. Between 2010 and 2022, prevalence of prenatal OUD doubled (as assessed at delivery: 0.15% to 0.30%; as assessed via prenatal OUD ED visits: 0.04% to 0.08%). Joinpoint analysis indicated that most of this increase occurred prior to 2018; annual percentage changes (APC) after 2018 were largely flat (at-delivery prevalence APC: 2.4%, 95% CI, -2.2% to 7.3%; ED prevalence APC: 1.4%, 95% CI, -7.0% to 3.8%). Differences in 2019-2022 vs. 2010-2018 prevalence of prenatal OUD were larger among non-Hispanic White and other/multiple-race individuals, and those covered by Medicaid.

Conclusions: The recent introduction of fentanyl to California was associated with only incremental increases in prevalence of prenatal OUD. Continued tracking of these trends is important for perinatal health.