The object of our investigation was to evaluate the potential of transvaginal echocardiography for a complete anatomic study of the fetal heart, and for detection of congenital heart diseases in low-risk pregnant patients between 13 and 15 weeks' gestation. High-frequency (6.5 MHz and 7.5 MHz) transvaginal probes were employed for fetal echocardiographic assessment. Six hundred and sixty patients considered at low risk for congenital heart disease underwent in utero ultrasonographic studies, neonatal records, postnatal imaging studies, and pathologic examination. The four-chamber view was obtained in 100% of the fetuses, while the extended fetal heart examination was completed in 98%. Six fetuses with cardiac defects were diagnosed during the study: three had major heart defects (aortic atresia, tetralogy of Fallot, and persistent truncus arteriosus), all detected at the early transvaginal scan; three cardiac anomalies escaped our early diagnosis; two fetuses had a minor ventricular septal defect diagnosed only postnatally; and one had multiple cardiac rhabdomyoma diagnosed in the third trimester. Our results demonstrate that between 13 and 15 weeks' gestation transvaginal echocardiographic assessment of the fetal heart in the low-risk population is feasible. Moreover, some severe anomalies may be detected at such an early gestational age.