First-trimester diagnosis of fetal congenital heart disease by transvaginal ultrasonography. 
To describe the feasibility of diagnosing fetal congenital heart defects by transvaginal ultrasonography during the first trimester of pregnancy.  Pregnant women presenting to the Ultrasonographic Unit at the Chaim Sheba Medical Center who had a diagnosis of fetal heart defects were reviewed retrospectively.  Attention was paid to prenatal ultrasound studies, karyotype, and pathologic examinations.  Using high-resolution transvaginal ultrasonography, we were able to detect fetal tachycardia (one case), ectopia cordis with ventricular septal defect (one case), atrioventricular septal defect (two cases), ventricular septal defect with persistent truncus arteriosus (one case), tetralogy of Fallot (two cases), and large right atrium with unguarded tricuspid valve (Uhl disease) (one case).  Seven of these fetuses had normal karyotypes and all showed additional sonographic abnormalities, including septated cystic hygroma (three cases), hydrops (ascites and pericardial effusions) (two cases), omphalocele (one case), and bilateral agenesis of kidneys (one case).  Only one fetus with an abnormal karyotype (45,XO) showed a combination of septated cystic hygroma with hydrops.  High-resolution duplex Doppler transvaginal ultrasonography during the first trimester of pregnancy seems to be a useful diagnostic method for detecting some congenital heart diseases.