In 95 percent of the cases, the child has three instead of two chromosomes on the 21 chromosome. There is a test called amniocentesis that can tell the mother if her child will have Down syndrome. Amniocentesis involves inserting a needle into the amniotic sac to withdraw a small about of the amniotic fluid. The cells in the fluid are then analyzed to see if the child has Down syndrome. There is small risk of a miscarriage or infection to the uterus. Women over the age of thirty-five are encouraged to take the test. Down syndrome is the most prevalent chromosomal disorder. There are slightly more boys born with the syndrome than girls. It is also seen in all ethnic groups. .
In most cases, the doctor will be able to recognize if the child has Down syndrome right after birth. They are mostly able to tell by the child's appreance. There are certain features that some, but not all Down syndrome children have.
1. The child with Down syndrome usually has a rounded face.
2. The back of the head is slightly flattened.
3. The eyes of nearly all children and adults with the syndrome slant slightly upwards. There is also a small fold of skin that runs between the inner corner of the eye and the nose.
4. The mouth is smaller than average and the tongue is larger.
5. The hands tend to be board with short fingers. The little finger sometimes has only one joint instead of two. .
6. The feet tend to be stubby and have a wide gap between the first and second toes.
7. Children with Down syndrome usually weigh less than average at birth. They are normally shorter than other children and tend to be overweight. .
8. They have flabby muscle tone and poor coordination due to less control over the motor nerves.
9. About one third of children born with Down syndrome will be having a heart abnormality. The most common being atrioventricular septal defect. This is when there is a hole between the two atria. About one in six children will have this abnormality.