Prenatal diagnosis of 22q11 microdeletion

Microdeletion of 22q11 is responsible for DiGeorge syndrome, velocardiofacial syndrome, congenital conotruncal heart defects, and related disorders. Familial transmission accounts for about 10-20 per cent of cases and most of the parents with deletions are nearly asymptomatic. This phenotypic variability makes it difficult to give appropriate genetic counselling. We report our experience on prenatal diagnosis of 22q11 deletion. We proposed prenatal detection of 22q11 microdeletion in 33 pregnancies. In two instances the parents refused prenatal diagnosis and one pregnancy ended spontaneously before the time of sampling. Fluorescent in situ hybridization (FISH) analysis on cultured amniotic cells with probes mapping in the commonly deleted region was used in the remaining 30 cases. Indications were classified into two groups. The first group included four couples with an abnormal family history of a deleted child and/or a deleted parent. No deletion was found in this group. The second one concerned pregnancies with a prenatally detected heart defect. Among these pregnancies with abnormal ultrasound findings, three deletions were found in the 26 samples tested.