Down syndrome is a genetic disorder which manifests as developmental problems. These problems affect a person's physical and mental capabilities. It occurs due to extra genetic material in the cells of the person. It is also called trisomy 21, because there is an extra chromosome (genetic material) of number 21 in the cells.

Generally, in the cells of our body, there are 46 chromosomes in 23 pairs. One pair of chromosomes comes from each of the parents. When either of the parents has one extra chromosome in their sperm or egg, the child has Down syndrome. This is why Down syndrome is called a genetic disorder.

The following symptoms are seen in children with Down syndrome:
-Small hands and fingers
-Small mouth
-Eyes slanting upwards
-Flattened nose
-2 creases on the palm instead of 3
-Short height
-Short neck
-Loose joints
-Birth defects in the heart

After the birth of the child, Down syndrome can be diagnosed by the doctor with the help of physical examination and blood test, which looks for the extra chromosomes in the cells.
Before birth, Down syndrome can be diagnosed by taking samples of the placenta or amniotic fluid from the mother to check the baby's cells for the extra chromosome.

Down syndrome is hereditary only in rare cases. It is seen that only 1 out of 100 cases of down syndrome are hereditary. Although, if your first child has Down syndrome, it is highly likely that a second child may also have it.