Down's Syndrome : Knowing it early

Down's syndrome, or trisomy 21 is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. This can be recognized early using prenatal screening. Individuals with Down syndrome may have some or all of the following physical characteristics:

1. oblique eye fissures with epicanthic skin folds on the inner corner of the eyes
2. muscle hypotonia (poor muscle tone)
3. congenital heart defects
4. single palmar fold
5. flat nasal bridge
6. white spots on the iris known as Brushfield spots
7. short neck
8. excessive joint laxity including atlanto-axial instability
9. a protruding tongue (due to small oral cavity, and an enlarged tongue near the tonsils),
10. excessive space between large toe and second toe, a single flexion furrow of the fifth finger, and a higher number of ulnar loop dermatoglyphs.

Prenatal screening

Nuchal scans. The scan is carried out at 11-13 weeks pregnancy and assesses the amount of fluid behind the neck of the fetus - also known as 'the nuchal translucency'. Fetuses at risk of Down tend to have a higher amount of fluid around the neck. The nuchal test is a Baby Ultrasound scan focusing on the thickness of skin at the back of the baby's neck. Thickened skin is commonly associated with Downs syndrome and other chromosome abnormalities.


Each pregnant woman's risk is estimated by a complex mathematical formula combining the results of the woman's hormone tests, her age, and the ultrasound measurement of the skin thickness on the back of the baby's neck (nuchal thickness). Other ultrasound features taken into account include nasal bone measurements. The accuracy of this non-invasive test is estimated at about 97%. The results, usually available within 24 hours, will then be given to the parents following full counselling. Further tests may be recommended.

If you have regular medical consultations, your doctor may require you to take the nuchal scans to check the possibility of the Down's syndrome.