Maternal methadone dosing schedule and fetal neurobehaviour.

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.