Fetal response to maternal methadone administration

Objective The purpose of this study was to investigate the effect of methadone on fetal neurobehavioral functions and maternal physiologic indicators. Study design Forty women attending a substance abuse treatment facility with otherwise uncomplicated pregnancies were evaluated at peak and trough methadone levels. Fetal measures included heart rate, variability, periodic accelerations/decelerations, motor activity, and fetal movement-heart rate coupling. Maternal measures included maternal heart period, variability, electrodermal skin conductance, respiration, and respiratory sinus arrhythmia (RSA). Repeated measure analysis of variance was used to evaluate within-subject changes. Results At peak methadone, fetal heart rate was slower, less variable, and displayed fewer accelerations. Fetuses displayed less motor activity, and the integration between heart rate and motor activity was attenuated. Maternal heart rate and skin conductance were unchanged, but methadone administration was associated with lower respiratory rate and RSA, an indicator of parasympathetic tone. Conclusion Maternal methadone administration has significant effects on fetal behavioral functions that are independent of maternal effects.