We report a prospective database evaluation of the occurrence of aneuploidy an d deletion 22q11.2 after prenatal detection of cardiac abnormalities. To ensure the maximum inclusion, all cardiac defects were considered, with the exception o f echogenic intracardiac foci. Prenatal specimens with ultrasound findings of ca rdiac defects were identified. Physicians were provided supplementary informatio n that described the risk of deletion 22q11.2 syndrome if the karyotype was norm al. On approval, fluorescence in situ hybridization was performed to identify th e 22q11.2 microdeletion. Prenatal detection of cardiac abnormalities identified aneuploidy or unbalanced chromosome rearrangements in 41%of the cases that were studied. In those fetuses with normal karyotypes, 3%had the deletion 22q11.2. These results indicate that prenatal ultrasound findings of congenital heart def ects identify fetuses who are at increased risk for chromosome abnormalities. Fe tuses with normal karyotypes should consider having fluorescence in situ hybridi zation studies for the microdeletion 22q11.2 syndrome. Chromosome and fluorescen ce in situ hybridization studies of family members should be recommended when a fetus is identified as having the deletion 22q11.2. We report a prospective database evaluation of the occurrence of aneuploidy an deletion 22q11.2 after prenatal detection of cardiac abnormalities. To ensure the maximum inclusion, all cardiac defects were considered, with the exception of echogenic intracardiac foci. Prenatal specimens with ultrasound findings of Physicians were rendered supplementary informatio n that described the risk of deletion 22q11.2 syndrome if the karyotype was norm al. On approval, fluorescence in situ hybridization was performed to identify th eqq12.2 microdeletion. Prenatal detection of cardiac abnormalities identified aneuploidy or unbalanced chromosome rearrangements in 41% of the cases that were studied. In those fetuses with normal karyotypes, 3% had the deletion 22q11.2. These results indicate that prenatal ultrasound findings of congenital heart def ects identify fetuses who are at increased risk for chromosome abnormalities. Fe tuses with normal karyotypes should consider having fluorescence in situ hybridi zation studies for the microdeletion 22q11.2 syndrome. Chromosome and fluorescen ce in situ hybridization studies of family members should be recommended when a fetus is identified as having the deletion 22q11.2.