A Cochrane review included 4 studies with a total of 271 pregnant women. Three compared methadone with buprenorphine and one methadone with oral slow-release morphine. For the women there was no difference in use of primary substance (RR 1.81, 95% CI 0.70 to 4.69; 2 studies, n=151) between methadone and buprenorphine but a trend towards lower drop-out rate from treatment in the methadone group (RR 0.64, 95% CI 0.41 to 1.01; 3 studies, n=223). Birth weight was higher in the buprenorphine group in 2 studies but not in the third study.Oral slow morphine seemed superior to methadone in abstaining women from the use of heroin RR 2.40 (95% CI 1.00 to 5.77, n=48) in one trial with methodological flows. There was no difference in APGAR score or in neonatal abstinence syndrome (NAS). Comparing methadone with oral slow morphine no differences for birth weight and mean duration of NAS were found.
Comment: The quality of evidence is downgraded by study limitations (high and differential loss to follow-up in the compared groups), by imprecise results (limited study size for each comparison), by indirectness (cigarette consumption was considered only in one trial), and by potential reporting bias (only few small trials reported).