There is lack of knowledge about the safety of treatment with methadone and buprenorphine as part of opioid maintenance treatment (OMT) during pregnancy. The purpose of this study was to examine neonatal outcomes concerning the use of OMT during pregnancy. We used nationwide registry linkages from the Czech Republic (2000-2014) and Norway (2004-2013). We compared prenatally OMT-exposed newborns with (a) newborns of women hospitalized with opioid use disorder during pregnancy in the Czech sample and (b) newborns with neonatal abstinence syndrome (NAS) in Norway. We performed multivariate linear and binary logistic regression exploring the associations between OMT and neonatal outcomes (growth parameters, gestational age, fetal death, small for gestational age, Apgar score, and NAS). Regression coefficients (b) and odds ratios (ORs) were estimated. The cohorts consisted of 333 Czech, and 235 Norwegian OMT-exposed newborns, and 106 and 294 newborns in the comparison groups, respectively. In both countries, the neonatal growth parameters were similar in the OMT and the comparison groups. In Norway, OMT exposure prolonged gestational age (adjusted b = 0.96 weeks, 95% confidence interval [CI] =0.39-1.53) while the odds of preterm birth and Apgar score at 5 minutes were lower than in the comparison group (adjusted OR = 0.35, 0.16-0.75 and aOR = 0.21, 0.06-0.78, respectively). Newborns of women in OMT had similar growth parameters as newborns of women with opioid use disorders who were not in OMT during pregnancy. Overall, our findings do not suggest that OMT results in worse neonatal outcomes.

Department of Addictology 1st Faculty of Medicine Charles University Prague Czech Republic

Department of Addictology 1st Faculty of Medicine Charles University Prague Czech Republic Institute of Health Information and Statistics of the Czech Republic Prague Czech Republic

Department of Addictology 1st Faculty of Medicine Charles University Prague Czech Republic National Monitoring Centre for Drugs and Addiction Office of the Government of the Czech Republic Prague Czech Republic

Department of Chronic Diseases and Ageing Norwegian Institute of Public Health Oslo Norway Department of Global Public Health and Primary Care University of Bergen Bergen Norway

Department of Mental Disorders Norwegian Institute of Public Health Oslo Norway

Department of Mental Disorders Norwegian Institute of Public Health Oslo Norway Norwegian Centre for Addiction Research at the University of Oslo Oslo Norway

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