Prenatal diagnosis of right aortic arch: associated anomalies and fetal prognosis according to different subtypes

Objectives: Right aortic arch (RAA) is a rare anomaly with an incidence of 0.1 % in the adult population and low-risk fetuses. Our aim in this study was to evaluate associated anomalies and conditions according to subtypes. Methods: This was a retrospective study examining consecutive pregnancies diagnosed with RAA in our hospital between 2018 and 2022. Fetuses with RAA were divided into three groups, RAA with right-sided ductus arteriosus (RAA-RDA), RAA with left-sided ductus arteriosus (RAA-LDA), and RAA with a double aortic arch (RAA-DAA). Results: A total of 81 fetuses were diagnosed as having RAA during the study period. The rate of cardiac anomalies (82.8 %) in the RAA-RDA group was higher than in the RAA-LDA (17.6 %) and RAA-DAA (22.2 %) groups (p<0.001). No statistically significant difference was found between the groups in terms of maternal age, diagnosis week, pregnancy outcome, extracardiac anomalies, and genetic anomalies. Three (8 %) of 36 fetuses with isolated RAA who resulted in live birth developed symptoms related to the vascular ring, and one (2.7 %) newborn with RAA-DAA underwent surgery. Conclusions: The incidence of cardiac anomalies is high in fetuses with RAA-RDA. Ultrasound examinations should be performed for cardiac anomalies and additional structural anomalies. Vascular ring formation is a rare but important complication due to compression risk to the trachea and esophagus.