Prenatal Diagnosis of the Right Aortic Arch: Change in Detection Rate, the Status of Associated Anomalies, and Perinatal Outcomes in 137 Fetuses

To evaluate prenatal findings of the right aortic arch (RAA), associated cardiac, extracardiac, and genetic anomalies, its perinatal outcomes and the need for postnatal interventions in cases of isolated RAA with a view to facilitating appropriate counseling. This was a multicenter, cohort study, that was undertaken in two international major cardiac centers between 2009 and 2020. The study subjects were prenatally diagnosed RAA cases with and without other structural cardiac defects. A RAA was identified in 137 fetuses. There were 84 cases of isolated RAA. Associations with additional intracardiac malformations were found in 53 (38.7%) cases. An extracardiac anomaly was observed in 26/137 (18.9%) fetuses, 11/84 (13.0%) fetuses with isolated RAA, and 15/53 (28.3%) fetuses with an additional intracardiac anomaly. The incidence of extracardiac and chromosomal anomalies was significantly higher in cases of RAA with abnormal intracardiac anatomy (28.3-18.8%, respectively), compared with RAA with normal intracardiac anatomy (13.0-5.9%, respectively) (p < 0.05). 22q11.2 microdeletion was found higher in RAA with CHD (4/18 fetuses) than isolated RAA (2/24 fetuses) (22.2% vs. 8.3% respectively). ALSA was present in 19.3% of cases. ALSA was more frequently observed in cases of isolated RAA (23.6%), than in RAA with structural CHD (7.6%) (p < 0.05). The pregnancy was interrupted in six fetuses, and one died in utero. The mortality rate was higher in fetuses with intracardiac anomaly than RAA without cardiac anomaly (11/49 (22.4%) vs. 2/81 (2.4%). Vascular ring formation was revealed in 21/98 cases. The RAA caused symptoms of a vascular ring in only one patient (0.7%) requiring surgery in the follow-up. Overall survival after initial diagnosis in the total cohort was 85.4% with 38 of 53 (71%) RAA with CHD cases and 79 of 84 (94.0%) isolated RAA cases. Chromosomal and extracardiac anomalies are lower in isolated RAA but not negligible hence amniocentesis should be routinely offered in all cases. The requirement for postnatal intervention in the immediate neonatal period is remote, therefore delivery of these fetuses need not be undertaken at a cardiac or surgical center.