Prenatal Sonographic Features of 22q11.2 Microdeletion Syndrome

Fetuses with 22q11.2 microdeletions (del22q11.2) have variable clinical expressions. Associated congenital anomalies include cardiac defects, abnormal facies, thymic hypoplasia or aplasia, velopharyngeal insufficiency, cleft palate, hypocalcaemia due to parathyroid aplasia or hypoplasia, and learning disability. Statistically, most cases are sporadic and only about 8% are inherited. The microdeletion can be easily diagnosed with fluorescence in situ hybridization or molecular analysis of fetal cells, but there is lack of definite indications for the prenatal diagnosis of sporadic cases with del22q11.2. Currently, ultrasound is viewed as a valuable tool in the detection of sporadic cases of del22q11.2 syndrome. This article provides an overview of the prenatal sonographic features of del22q11.2 syndrome, including cardiovascular abnormalities, thymic hypoplasia or aplasia, intrauterine growth restriction, urinary abnormalities, increased nuchal translucency thickness, and abnormal amniotic fluid levels. Among these abnormalities, prenatal cardiac involvement is a prominent feature, especially conotruncal cardiac defects. The additional visualization of fetal thymus and detection of intrauterine growth restriction on obstetric ultrasound can enhance the detection rate of del22q11.2. Prenatal testing for 22q11.2 deletion should therefore be considered when a conotruncal cardiac defect accompanying other associated abnormalities are detected on prenatal ultrasound. Owing to the phenotypic diversity of 22q11.2 microdeletion syndrome, increasing awareness and knowledge of fetal abnormalities on prenatal ultrasound will be helpful in the prenatal detection of del22q11.2. Early diagnosis of fetuses with del22q11.2 could help obstetricians, surgeons, pediatric cardiologists and geneticists in the decision-making process for prenatal, perinatal or postnatal care.