[Difficulties in interpreting the cardiotocogram in atrioventricular arrhythmia of the fetal heart]

During a routine screening examination of a pregnancy during the 28th gestational week, a pericardial effusion and ascites were recognized in the fetus. Ultrasound B- and M-mode evaluation (echocardiography) revealed an atrio-ventricular block grade III with commencing cardiac insufficiency. Cardiac monitoring (CTG) by ultrasound (HP 8040A Fetal Monitor) documented primarily the fetal atrial activity when the logic switch was turned off, but after it was turned on there was no continuous recording. When fetal heart action was recorded by abdominal electrocardiogram (AFEKG) the cardiotocography showed simultaneously a ventricular frequency of 50/min. and a maternal frequency of 70-80/min. This case confirms that the registration of fetal heart action without real-time imaging is only of limited value in cases of cardiac-conduction anomalies. It is important that during ultrasound screening examination, the cardiac heart action is carefully evaluated.