A 27 weeks gestation fetus, evaluated because of polyhydramnios, was found by echocardiography to have an interrupted aortic arch type B. Because of the known association between this malformation and DiGeorge syndrome, an amniocentesis was performed. Fluorescence in situ hybridization revealed a 22q11 deletion. This is, to our knowledge, the first report of prenatal detection of a fetus with 22q11 deletion in the absence of a family history.