Abstract
A method for electronic supervision of the human fetus based upon controlled sound stimulation of the fetus and the fetal heart rate response was used to evaluate the effect of pethidine on the fetus. Half an hour after intramuscular injection of 100 mg pethidine in the mother, the fetal heart rate response to sound stimulation was already depressed in 10 out of 20 cases. A general depression of the heart rate response to sound was found 2 and 3 hours after the injection. The fetal heart rate response to sound stimulation seems to constitute a sensitive record of pethidine's influence.