Congenital heart block (CHB), defined as an atrioventricular block diagnosed in utero, at birth, or within the neonatal period (0-27 d after birth), is a rare disorder closely linked to transplacental transport of maternal antibodies anti-Ro/SSA and anti-La/SSB. These antibodies may induce a myocarditis, or interact directly with calcium channel proteins with disturbance of transmembrane signaling at the level of the conduction tissue, or interfere with apoptosis. Depending on the severity of the process, the fetus may die in utero or a few days after birth or survive to the perinatal period and have a near-normal life; in most survivors a pace-maker must be implanted. Skin lesions, haematological disorders, and hepatic cholestasis are other transient clinical features of the syndrome. Sinus bradycardia and QT interval prolongation may be observed as well in babies born from anti-Ro/SSA positive mothers. The risk of recurrence of complete block ranges from 10-17%. Most of the mothers are asymptomatic at delivery and are identified only by the birth of an affected child. Their long-term outcome generally is more reassuring than previously assumed and arthralgias and dry eyes are the most common symptoms. A standard therapy for blocks detected in utero still does not exist. The prevalence of complete CHB in newborns of anti-Ro/SSA positive women and with known connective-tissue disease was 2%. Serial echocardiograms and obstetric sonograms, performed at least every 2 wk starting from the 16 wk gestation, are recommended in anti-Ro/SSA positive pregnant women.