Congenital long QT syndrome (LQTS) is a disorder of myocardial repolarization and is characterized by a prolonged QT interval on an electrocardiogram. A prolonged QT predisposes patients to an increased risk of syncope and sudden cardiac death secondary to polymorphic ventricular tachycardia. Several mutations linked to the LQTS have been identified, the most common of which have been found in the potassium channel KCNQ1 (LQT1) and hERG (LQT2) genes and in the sodium channel SCN5A (LQT3) gene. Female sex is an independent risk factor for the development of torsades de pointes in LQTS. Furthermore, although pregnancy may be associated with protection against cardiac events in LQTS, the 9-month postpartum period represents a time of increased arrhythmogenicity. Interestingly, these cardiac events during the postpartum period are more common in patients with LQT2. The precise mechanisms that influence the cardiac repolarization during the postpartum period are unclear. Beta-blockers are considered reasonably safe during pregnancy and should be continued or initiated in patients with LQTS to reduce the risk of cardiac events. Implantable cardioverter defibrillators are safe in pregnancy, and there is no evidence that pregnant women with these devices are at any greater risk for adverse complications solely on the grounds of having the device.