Associated Chromosomal Abnormalities in Fetuses Diagnosed Prenatally with Right Aortic Arch

Right aortic arch (RAA) is an abnormal embryologic development of the aorta characterized by its descendance on the right side of the trachea. This anomaly is accompanied often by other intracardiac and extracardiac anomalies and it is also known for potential association with genetic aberrations, most common being 22q11.2 deletion. The aim of the study was to evaluate the incidence of chromosomal anomalies and in particular 22q11.2 deletion in RAA. Moreover, we assessed the prognosis of fetuses with isolated RAA. Our second objective was to evaluate the prevalence of hypoplastic or absent thymus in RAA fetuses diagnosed with 22q11.2 deletion. We conducted a retrospective study of all fetuses with RAA over a period of 10 years diagnosed prenatally in a tertiary referral center in Romania. A detailed ultrasound was obtained in each case. We extracted the cases that were investigated genetically and selected the cases positive for 22q11.2 deletion. These fetuses were followed up until pregnancy termination or birth to confirm the ultrasound findings. Deletion 22q11.2 was present in 23.52% (4/17) cases. The incidence was particularly high when the fetuses presented a small thymus. In conclusion, we believe that all cases of RAA, including when isolated, should be referred for genetic testing and especially 22q11.2 deletion exclusion. Also, we suggest considering hypoplastic thymus to be a soft marker for this deletion.