Combined echocardiographic and Doppler assessment of fetal congenital atrioventricular block.

Fetal heart rate monitoring was combined with fetal echocardiography for examination of atrial reactivity during labour in five fetuses with second or third degree heart block. Alterations in vagal tone accompanying uterine contraction influence atrial rate, even when the ventricle is not under atrial 'control'. Fetal echocardiography enabled diagnosis of the underlying basis of the arrhythmia and located the optimal position for recording atrial activity with an external heart rate monitor. External and internal monitoring of atrial activity demonstrated reactivity during labour. Two patients were delivered vaginally after monitoring throughout labour. One mother preferred elective caesarean delivery. Caesarean section was required in another for cephalopelvic disproportion and in the remaining woman for late decelerations. These monitoring techniques provide an assessment of fetal well-being in the presence of fetal bradycardia due to variable degrees of heart block.