Fetal neurobehavioral effects of exposure to methadone or buprenorphine.

As part of a double-blind study of medication treatment for opioid dependence during pregnancy, 17 opioid-dependent pregnant women maintained on either buprenorphine or methadone underwent fetal monitoring at 24, 28, 32, and 36 weeks gestation. Maternal demographic information and infant outcomes did not significantly differ by medication group. Earlier in gestation (24 and 28 weeks), buprenorphine-exposed fetuses had higher levels of fetal heart rate variability, more accelerations in fetal heart rate and greater coupling between fetal heart rate and fetal movement than the methadone-exposed group (all ps < .05). Later in gestation (32 and 36 weeks), buprenorphine-exposed fetuses displayed less suppression of motor activity and longer duration of movements than the methadone-exposed group (all ps < .05). These results may have implications for the optimal treatment of the opioid-dependent pregnant woman.