Retention in Buprenorphine versus Methadone Treatment for Opioid Use Disorder in Pregnancy and Postpartum

Background: Retention in medicated treatment for opioid use disorder (MOUD) is crucial for maternal and neonatal safety in pregnant patients with OUD. While several clinical trials demonstrate higher treatment retention for methadone compared with buprenorphine outside of pregnancy, evidence during pregnancy is more limited.

Objectives: The study aim was to assess retention in MOUD during pregnancy and through 1-year postpartum.

Methods: Using nationwide Medicaid data from 2003 to 2018, we conducted a cohort study that included pregnant patients who initiated methadone or buprenorphine for OUD during the first trimester. In the main analysis, treatment discontinuation was assigned 60 days after the last treatment record, and switching between MOUD was allowed. Treatment discontinuation was assessed from initiation until (i) end of pregnancy, and (ii) 1-year post-partum. Hazard ratios (HR) were estimated using Cox proportional hazards regression with propensity score overlap weights for confounding control. Several sensitivity analyses were performed, including extending the treatment gap to 90 days, censoring at treatment switch, and censoring at initiation+9 months instead of at delivery to account for differential length of follow-up for preterm versus term deliveries. In addition, we estimated the proportion of months covered (PMC) as months with evidence of treatment divided by total months in the study period. Odds ratios (OR) for PMC < 80% were estimated using logistic regression.

Results: We identified 701 and 1695 pregnancies initiating methadone and buprenorphine, respectively. Compared to methadone initiators, buprenorphine initiators were more likely to discontinue treatment during pregnancy (33% for buprenorphine vs. 25% for methadone; weighted HR=1.37, 95%CI 1.13-1.67) and through 1-year postpartum (59% vs. 48%; HR=1.36, 1.18-1.56). Extending the treatment gap to 90 days (HR=1.33, 1.07-1.66 during pregnancy; HR=1.33, 1.15-1.55 through postpartum), censoring at switching (HR=1.39, 1.15-1.68 during pregnancy; HR=1.37, 1.19-1.58 through postpartum), and censoring at initiation+9 months (HR=1.32, 1.10-1.58) showed consistent results with the main analysis. Similarly, buprenorphine initiators were more likely to have a PMC < 80% than methadone initiators (weighted OR=1.42, 1.13-1.77 during pregnancy; OR=1.57, 1.28-1.91 through postpartum).

Conclusions: Pregnant patients initiating buprenorphine during early pregnancy are more likely to discontinue treatment than those initiating methadone. Our findings highlight the importance of identifying and addressing barriers to treatment retention among pregnant patients with OUD.