Maternal methadone dosing schedule and fetal neurobehaviour

Daily methadone maintenance is the standard of care for opiate dependency during pregnancy. Previous research has indicated that single-dose maternal methadone administration significantly suppresses fetal neurobehaviours. The purpose of this study was to determine if split-dosing would have less impact on fetal neurobehaviour than single-dose administration.

Forty methadone-maintained women were evaluated at peak and trough maternal methadone levels on single- and split-dosing schedules. Monitoring sessions occurred at 36- and 37-weeks gestation in a counterbalanced study design. Fetal measures included heart rate, variability, accelerations, motor activity and fetal movement-heart rate coupling (FM-FHR). Maternal measures included heart period, variability, skin conductance, respiration and vagal tone. Repeated measure analysis of variance was used to evaluate within-subject changes between split- and single-dosing regimens.

All fetal neurobehavioural parameters were suppressed by maternal methadone administration, regardless of dosing regimen. Fetal parameters at peak were significantly lower during single versus split methadone administration. FM-FHR coupling was less suppressed from trough to peak during split-dosing versus single-dosing. Maternal physiologic parameters were generally unaffected by dosing condition.

Split-dosed fetuses displayed less neurobehavioural suppression from trough to peak maternal methadone levels as compared with single-dosed fetuses. Split-dosing may be beneficial for methadone-maintained pregnant women.