Developmental characteristics of fetal arrhythmias during the period from intrauterine to early extrauterine life assessed using dual echocardiography.

To evaluate the outcome of fetal arrhythmias, serial echocardiographic examinations were made on 29 fetuses between 18 and 41 weeks gestation, including 23 with premature contractions (PCs) and 6 with complete atrioventricular block (AVB). Of the cases of PCs 43.5% (10/23) disappeared spontaneously during the antenatal period. 39.1% (9/23) converted to a normal sinus rhythm in early neonatal life, while 17.4% (4/23) had complications of either atrial or ventricular tachycardia. All with AVB (6/6) remained, regardless of advance in gestational age and continued through to the postnatal period. PCs and AVB indicate functional error and an impairment during development of the conduction system, respectively.