Neonatal outcomes following in utero exposure to methadone or buprenorphine: A national cohort study of opioid-agonist treatment of pregnant women in Norway from 1996 to 2009

Abstract

Background
In Norway, most opioid-dependent women are in opioid maintenance treatment (OMT) with either methadone or buprenorphine throughout pregnancy. The inclusion criteria for both medications are the same and both medications are provided by the same health professionals in any part of the country. International studies comparing methadone and buprenorphine in pregnancy have shown differing neonatal outcomes for the two medications.

Method
This study compared the neonatal outcomes following prenatal exposure to either methadone or buprenorphine in a national clinical cohort of 139 women/neonates from 1996 to 2009.

Results
After adjusting for relevant covariates, buprenorphine-exposed newborns had larger head circumferences and tended to be heavier and longer than methadone-exposed newborns. The incidence of neonatal abstinence syndrome (NAS) and length of treatment of NAS did not differ between methadone- and buprenorphine-exposed newborns. There was little use of illegal drugs and benzodiazepines during the pregnancies. However, the use of any drugs or benzodiazepines during pregnancy was associated with longer lasting NAS-treatment of the neonates.

Conclusions
The clinical relevance of these findings is that both methadone and buprenorphine are acceptable medications for the use in pregnancy, in line with previous studies. If starting OMT in pregnancy, buprenorphine should be considered as the drug of choice, due to more favorable neonatal growth parameters. Early confirmation of the pregnancy and systematic follow-up throughout the pregnancy are of importance to encourage the women in OMT to abstain from the use of tobacco, alcohol, illegal drugs or misuse of prescribed drugs.