A fetal Wolff-Parkinson-White syndrome diagnosed prenatally by magnetocardiography.

We report a case of fetal Wolff-Parkinson-White (WPW) syndrome diagnosed prenatally by magnetocardiography (MCG). At 32 weeks' gestation, the fetus was diagnosed to have a paroxysmal supraventricular tachycardia by ultrasonography and direct fetal electrocardiogram (ECG). Transplacental fetal therapy by maternal oral administration of propranolol resolved the fetal tachyarrhythmia. Although the wave forms of the fetal MCG at 32 weeks' gestation were normal, the fetal MCG at 35 weeks' gestation showed a short PR interval and a long QRS complex duration with a delta wave, indicating WPW syndrome. The findings of the fetal MCG were confirmed by the postnatal ECG. MCG made the prenatal diagnosis of WPW syndrome possible.