Characteristics of prenatally detected right aortic arch cases in a single institution

This study aimed to elucidate the diagnostic process, the associated anomalies and the perinatal outcomes of right aortic arch (RAA) in a group of low-risk patients. The obstetric imaging database and digital patient files were reviewed between January 2015 and June 2016. There were 12 RAA cases detected prenatally. Seven foetuses had an aberrant left subclavian artery and one foetus had mirror image branching. The prevalence of RAA was 1.8 in 1000. Invasive prenatal diagnosis was offered to patients and seven tests were performed. There was one associated cardiac anomaly (8.3%) and one extra-cardiac anomaly (8.3%) in the same foetus which cordocentesis revealed trisomy 21. There were also two 22q11.2 microdeletion cases with isolated RAA with aberrant left subclavian arteries. All patients have given live births except one patient has chosen a termination of pregnancy for 22q11.2 microdeletion. The median follow-up time of the newborns was 21 months. None of the babies required surgery for RAA during follow-up. All the babies are alive, except for the one with trisomy 21, who dead at 5 months due to the surgical complications of an oesophageal atresia operation. Patients with an RAA foetus should be offered for foetal karyotyping and analysis for 22q11.2 microdeletion. When isolated, RAA has usually a good prognosis and rarely requires cardiac surgery. Impact Statement What is already known on this subject? Prenatal diagnosis of RAA should prompt a detailed cardiac and extra-cardiac ultrasound examination. When isolated, RAA is associated with 22q11 deletion and aneuploidies in 4.6% and 5.1%, of cases respectively. What the results of this study add? Our study showed that 28.5% of isolated RAA cases are associated with 22q11.2 microdeletion. Cardiac surgery is rarely required when RAA is an isolated anomaly. What the implications are of these findings for clinical practice and/or further research? Invasive prenatal testing for karyotypes and 22q11.2 microdeletion should be offered to patients with RAA, even in the case of an isolated one. Further larger studies are needed to confirm this finding.