Trends in Prenatal Opioid Use Disorder in California, 2010-2022

Opioid-related deaths among perinatal populations have increased sharply in the U.S. Whether the recent ascendance of illicit fentanyl and other synthetic opioids in the drug supply translates to an increase in prenatal opioid use disorder remains unknown. This study investigated whether California's comparatively late fentanyl influx, in 2019, was associated with a subsequent increase in opioid use disorder among pregnant people.

This ecologic, repeated retrospective cohort study examined annual cohorts of individuals with an index live-birth delivery in California from 2010 to 2022. Analyses used statewide, all-payer linked hospitalization and emergency department records. Overall and subgroup-specific trends in the prevalence of prenatal opioid use disorder, assessed using International Classification of Diseases, Ninth Revision, Clinical Modification/ICD-10-CM diagnoses recorded at delivery hospitalization and during prenatal emergency department visits, were examined using joinpoint and logistic regression analyses. Data analysis was conducted in 2025.

The study included 4,381,064 index deliveries. Between 2010 and 2022, the prevalence of prenatal opioid use disorder doubled (as assessed at delivery: 0.15%-0.30%; as assessed via prenatal opioid use disorder emergency department visits: 0.04%-0.08%). Joinpoint analysis indicated that most of this increase occurred before 2018, with annual percentage changes after 2018 being largely flat (annual percentage change in at-delivery prevalence, 2.4% [95% CI= -2.2%, 7.3%]; annual percentage change in emergency department visit prevalence, 1.4% [95% CI= -7.0%, 3.8%]). Differences in the 2019-2022 versus 2010-2018 prevalence of prenatal opioid use disorder were larger among non-Hispanic White and other/multiple race individuals, as well as those covered by Medicaid.

The recent introduction of fentanyl to California was associated with only incremental increases in the prevalence of prenatal opioid use disorder. Continued tracking of these trends is important for perinatal health.