Early ultrasound diagnosis of fetal congenital heart defects in high-risk and low-risk pregnancies

Objective: To evaluate the yield of early second-trimester transvaginal ultrasonography in the detection of congenital heart defects among patients with low or high risk for fetal anomalies. Methods: During 5 years, we performed 12,793 transvaginal ultrasound examinations at 12-16 weeks’ gestation, targeted for detection of fetal congenital anomalies. Three thousand four hundred fifty-three (27%) of these patients were considered to be at high risk for fetal congenital heart defects (because of family or medical history or teratogen exposure). The other 9340 patients were considered to be at low risk for fetal anomalies. The four-chamber view and the outflow tracts were evaluated systematically in all patients. Results: Congenital heart malformations were observed in 47 cases, most of which (29 of 47) were diagnosed in the low-risk group. Additional extracardiac malformations were observed in 29 (62%) of the affected fetuses. Ten of 28 affected pregnancies that were karyotyped (36%) had abnormal chromosomes. Use of the four-chamber view alone would have failed to detect 11 (23%) of the abnormal fetuses. Conclusions: Transvaginal ultrasonography in the early second trimester is a useful tool for the detection of fetal cardiac structural defects, provided that both the four-chamber view and the outflow tracts are evaluated. When such an anomaly is suspected, additional fetal malformations should be sought and fetal karyotype should be determined.