Atrioventricular block in the newborn period

Congenital atrioventricular block (AVB) is a rare condition affecting 1 in 14,000–20,000 births.1 In the absence of congenital heart disease, the etiology is most frequently immune-based, thought to be connected to maternal anti-Ro antibodies.2 Patients exhibit fetal bradycardia, classically starting after the second trimester.1,2 The combination of fetal bradycardia, which can be significant, and myocardial inflammation leading to endocardial fibroelastosis together can lead to fetal hydrops and even fetal demise.