Clínica de Diagnóstico por Imagem (CDPI), Rio de Janeiro, Brazil

Trisomy 21 is an abnormality due to the presence of an extra copy of chromosome 21. It is the most common single cytogenetic aberration in live born infants. This chromosomal disorder occurs around 1:800 liveborn. First trimester screening has a  detection rate of 80% with 5% false positive. The risk factors include:

• advanced maternal age
• history of previous baby with trisomy 21
• specific ultrasound abnormalities such as hydrops, cystic hygroma, brachycephaly, protuberant tongue, low-set ears, short nose, thickened nuchal fold, choroid plexus cysts, mild ventriculomegaly, clinodactyly, ventricular septal defect, atrial septal defect, endocardial cushion defect, pulmonary stenosis, pulmonary hypoplasia, calcification of the chordae tendinea, duodenal atresia, echogenic bowel, pyelectasis, imperforate anus, intrauterine growth restriction, nonimmune hydrops, polyhydramnios.

The diagnosis can be done by karyotyping fetal cells obtained by chorionic villus sampling, amniocentesis or cordocentesis.

Fetal profile with prominent tongue

Fetus with trisomy 21 at 28 weeks. In the face (3D view) note the prominent tongue, relative nasal hypoplasia and small mouth.

Hands view shows short phalanges and hypoplasia of mid phalanx of fifth finger

Axial view of the abdomen showing the duodenal atresia

Axial view of the thorax showing right hydrothorax

Complete atrioventricular septal defect:

Pyelectasis