This document summarizes the diagnosis and treatment of fetal bradyarrhythmias. It discusses that fetal bradycardias can be caused by blocked atrial bigeminy, sinus bradycardia, fetal distress, congenital heart disease, long QT syndrome, or atrioventricular block. Atrioventricular block occurs in 70% of cases and can be associated with congenital heart disease, isolated and immune-mediated, or functional 2:1 AV block in long QT syndrome. For isolated congenital AV block that is antibody-mediated, treatment with corticosteroids may help but outcomes depend on gestational age and heart rate at diagnosis. Postnatal pacemaker implantation is often needed, especially if risk factors like