Fetal response to maternally administered morphine

OBJECTIVE: We sought to determine the effects of maternally administered morphine on fetal response. STUDY DESIGN: Singleton pregnancies requiring fetal blood sampling were enrolled. Only study patients were given morphine intramuscularly. Maternal vital signs, fetal heart rate, biophysical profile score, and umbilical artery Doppler indices (systolic/diastolic ratio, resistance index, and pulsatility index) were completed before and after fetal blood sampling. Maternal and cord blood morphine concentrations were measured. RESULTS: Ten study and 6 control patients were enrolled. A significantly lower biophysical profile score was observed in study patients (P = .001) as a result of absent fetal breathing movements and nonreactive non-stress tests. Gross and fine fetal movements were unaffected. A significant correlation was measured between the biophase morphine concentration and each of the Doppler indices. CONCLUSION: Morphine administered to the mother causes a significant decrease in the biophysical profile score. Correlation between the biophase morphine concentration and the Doppler indices was calculated. These results suggest that morphine acts as a vasoconstrictor of the placental vasculature but do not support the use of intramuscular morphine to suppress fetal movement.