Fetal cardiac arrhythmias are increasingly more frequently discovered by cardiotocographic monitoring beginning at the 30th week of gestation. The computation of systolic time intervals represents a noninvasive technique to evaluate the cardiovascular performance of these fetuses. The pre-ejection period, ventricular ejection time and duration of systole of 41 healthy fetuses, two fetuses with supraventricular tachycardia and one with complete atrio-ventricular block were computed on the basis of abdominal fetal electrocardiogram and phonocardiogram. One fetus with supraventricular tachycardia had a pathologic prolonged pre-ejection period and duration of systole. This fetus became acidotic during delivery and died from persistent cardiac arrhythmia and congestive heart failure after 2 years. Further investigations should be done in order to prove, if a prolonged pre-ejection period and duration of systole have a significant value. According to the present experiences of the author a vaginal delivery can be recommended, if normal systolic time intervals exist in the arrhythmic fetus.