Abstract
Background: Detecting rate of congenital heart defects（CHD）with biventricular heart has been still low, while univentricular heart has been rather easily detected through a fetal four chamber view（4CV）. The observation of ventricular outflow tract is a crucial step to successful detection of biventricular heart defects.
Objects: To evaluate the occurrence rate of the right aortic arch（RAA）among fetal diagnosed heart defects and assess the usefulness of RAA in the fetal screening.
Materials and Methods: Total of 3,557 fetuses were enrolled in the present study, in which fetal echocardiography was performed from 1993 to 2010. Records on video tapes and medical records were retrospectively reviewed.
Results: The incidence of RAA was 12.9％ among fetuses with CHD. The incidence of CHD was 81.0％ among fetuses with RAA. Cono-tranchal anomaly were most often associated with RAA, 38.2％in tetralogy of Fallot, 18.9％ in double outlet right ventricle, 24.1％ in transposition of great arteries. Among genetic syndromes, 22q11.2 deficiency syndrome was highly associated with RAA（75.0％）, although trisomy 13（0％）, trisomy 18（5.8％）, trisomy 21（5.4％）were rarely associated with RAA.
Conclusion: It is suggested that RAA is a useful marker of CHD in fetal screening, especially for cono-truncal anomaly which is technically difficult to detect through 4CV. Furthermore, RAA might be a new and useful marker for cardiac defects in genetic syndrome because it is rarely associated with trisomy and, highly with 22q11.2 deficiency syndrpome.
