Aim To determine pre- and post-dosing effects of prenatal methadone compared to buprenorphine on fetal wellbeing.
Design A secondary analysis of data derived from the Maternal Opioid Treatment: Human Experimental Research
(MOTHER) study, a double-blind, double-dummy, randomized clinical trial. Setting Six United States sites
and one European site that provided comprehensive opioid-dependence treatment to pregnant women.
Participants Eighty-one of the 131 opioid-dependent pregnant women completing the MOTHER clinical trial,
assessed between 31 and 33 weeks of gestation. Measurements Two fetal assessments were conducted, once before
and once after study medication dosing. Measures included mean fetal heart rate (FHR), number of FHR accelerations,
FHR reactivity in the fetal non-stress test (NST) and biophysical profile (BPP) score. Findings Significant group
differences were found for number of FHR accelerations, non-reactive NST and BPP scores (all Ps < 0.05). There were
no significant group differences before time of dosing. Significant decreases (all Ps < 0.05) occurred from pre- to
post-dose assessment for mean FHR, FHR accelerations, reactive NST and fetal movement. The decrease in accelerations
and reactive NST were significant only for fetuses in the methadone group, and this resulted in a significantly
lower likelihood of a reactive NST compared to fetuses in the buprenorphine group. Conclusion Buprenorphine
compared with methadone appears to result in less suppression of mean fetal heart rate, fetal heart rate reactivity and
the biophysical profile score after medication dosing and these findings provide support for the relative safety of
buprenorphine when fetal indices are considered as part of the complete risk–benefit ratio.