AbstractObjectiveTo examine our experience of the detection of a right aortic arch in the fetus over an 8‐year period.MethodsBetween February 1998 and December 2005, all patients prospectively diagnosed with a right aortic arch at our center were identified from our database and the videotape reviewed. In addition, the videotapes of 300 normal and 110 abnormal arbitrarily selected fetal echocardiograms, as well as 123 cases of tetralogy of Fallot and nine of a common arterial trunk were reviewed. Data including indication for fetal echocardiography, gestational age at diagnosis, karyotype, nuchal translucency measurement and outcome were collected.ResultsA right aortic arch was diagnosed prospectively in 55 fetuses and in a further 20 on retrospective videotape review. There were 21 examples of isolated aortic arch and four thought to have a double arch. A right arch was found in association with additional intracardiac malformations in 50 cases. The detection rate of a right aortic arch increased over the study period. The majority of patients were referred for a suspicion of congenital heart disease on obstetric scanning. Mean gestational age at diagnosis was 21 weeks. The karyotype including 22q11 status was known in 45/75 cases. There were 23 confirmed karyotypic anomalies, 12 of which were 22q11 deletions, occurring in 2/25 of the isolated group and 10/48 of the complex group, with a further two complex cases that were likely to have had 22q11 microdeletions. There were 29 pregnancy interruptions, four intrauterine deaths, 31 live births, four neonatal deaths and three patients lost to follow‐up. The remaining four pregnancies are continuing. Of the four with suspected double arch, three were confirmed postnatally.ConclusionThe diagnosis of a right‐sided aortic arch can be made by fetal echocardiography, either as an isolated lesion or in association with other cardiac malformations, from as early as 12 weeks' gestation. It can be difficult to distinguish from a double arch. Its increasing incidence over time in our series probably indicates that the diagnosis was previously overlooked. Karyotyping in the absence of other abnormal findings may be unnecessary in every case, but establishment of 22q11 microdeletion status in those cases with other anomalies is important. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.