Methadone and Gestational Weight Gain [21E

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INTRODUCTION: Treatment of patients with opioid use disorder (OUD) with either methadone or buprenorphine is recommended in pregnancy. An association between weight gain and methadone has been reported outside of pregnancy. We sought to identify factors associated with excessive gestational weight gain in patients with OUD on methadone. METHODS: This is a retrospective cohort study of pregnant patients with OUD treated with methadone at our institution from 2012–2017. The primary outcome was gestational weight gain. We compared women with non-excessive vs. excessive gestational weight gain based on Institute of Medicine (IOM) guidelines, based on pre-gestational body mass index (BMI). Chi square and t-tests were used to compare baseline characteristics. Linear regression was used to determine an association between methadone dose and gestational weight gain, and multiple linear regression was used to adjust for covariates. RESULTS: There were 289 patients identified. Characteristics were similar between groups, with the exception of methadone dose (133.37 mg non-excessive weight gain vs. 150.57 mg excessive weight gain; 95% CI -32.28, -2.12; P=.026). There was a significant association between methadone dose and gestational weight gain (Pearson R=0.12; unstandardized β=0.036; 95% CI 0.002, 0.07; P=.04). In multiple linear regression, there was an inverse relationship between initial BMI and gestational weight gain (unstandardized β=-0.88; 95% CI 1.40, -0.35; P=.001). The association with methadone dose remained significant after adjusting for covariates (unstandardized β=0.057; 95% CI 0.016, 0.098; P=.007). CONCLUSION: Higher methadone dose is associated with increased gestational weight gain. Further study is needed to determine the nature of this association.