Prenatal diagnosis of complete transposition of the great arteries at 12 weeks of gestation in a fetus with normal nuchal translucency: a case report

Abstract

Introduction: Complete transposition of the great arteries (TGA) is a common cardiac malformation with atrioventricular concordance and ventriculoarterial discordance with and incidence of 20-30 per 100,000 cases. While prenatal diagnosis of TGA remains challenging, especially in the first trimester ultrasound scan, advances in ultrasound equipment and sonographer training have resulted in an increased detection rate (from 12.5% to 72.5%) in the last decades.

Case Presentation: We present the case of a 31-year-old Caucasian primigravida with no medical or family history of congenital anomalies, who attended our unit for the routine first trimester ultrasound examination. The initial scan revealed a singleton live fetus with a gestational age of 12 weeks and a normal nuchal translucency, nasal bone, flow pattern in the ductus venosus and no regurgitation in the tricuspid valve of the fetal heart. While the four-chamber view of the heart appeared normal, careful examination of the outflow tracts failed to show the crossing of the pulmonary artery with the aorta. The parallel course of the great arteries confirmed the diagnosis of complete transposition of the great arteries.

Conclusion: Examination of the two outlet echocardiographic views during the 11 - 13+6 ultrasound scan by obstetric sonographers allows for early detection of TGA. The presence of TGA warrants a thorough anomaly scan and genetic counselling as TGA is associated in 10% of the cases with other noncardiac malformations. Finally, antenatal detection of TGA results in better clinical status before surgery and improved postoperative outcome of the neonate.