Etiology
Trisomy 21 : 95%
Translocation or mosaicism : 3-5%
Features
- Mental retardation
- Characteristic face : Large tongue, slanting eyes, abnormal teeth
- Brush field spots on iris
- Congenital heart lesions
- Single simian crease
- Cataract
Diagnosis
1st and 2nd trimester diagnostic options
- Combined test : Ultrasound to measure nuchal translucency + blood tests (beta-hCG and Pregnancy Associated Plasma Protein A : PAPP-A)
- Quad screen : Measures maternal serum alpha-fetoprotein, unconjugated estriol, hCG, and inhibin-A.
- Integrated test : Combination of the quad screen,PAPP-A, and nuchal translucency
- Cell-free fetal DNA : blood obtained by venipuncture in mother
3rd trimester : Ultrasound