Prenatal molecular genetic diagnosis of congenital long QT syndrome by strategic genotyping.

We demonstrate how genetic testing enabled a molecular prenatal diagnosis of congenital long QT syndrome in a 20-week fetus presenting with fetal bradycardia in the setting of maternal beta-blocker therapy. Before prenatal testing, strategic genotyping, based on a family history of a near drowning, was performed on a 3-generation family with clinically diagnosed long QT syndrome in which the affected mother was pregnant.