Nikita Mishra, New Delhi: Pregnancy is the best time of a woman's life, but a to-be mother's worst nightmare is that she could be carrying a baby which is at a high risk of developing a chromosomal abnormality or "Down's Syndrome".

Senior Consultant Fetal Medicine Apollo hospital, Dr Anita Kaul says, "Down's Syndrome is the most common cause of genetic problems in children of mental retardation worldwide." Down's Syndrome is caused by a slight change in one of the genes in the egg at the time of conception.

Three in 2000 babies are born with a chromosomal abnormality, that is mental retardation, heart defects, sexual infertility, growth and behavioral abnormalities. And it doesn't end there. Ninety per cent cases end with the death of the child in the first year. What makes the situation worse is that tests done to detect Down's Syndrome in babies are rare in India.

The screening for Down's Syndrome is usually done at a late stage in the second trimester, but by then it is too late to abort. Doctors are suggesting that this detection should be done in the first trimester so that the woman does not have to go through the pain of delivery — something which can be traumatic both physically and emotionally.

The screening for Down's Syndrome is a two way procedure. First, an ultrasound is done where an expert checks for fetal abnormalities. If the woman tests positive, then a blood test is done where the sample is taken from the womb. The second part of the test is more serious and doctors believe that one in 200 cases can end in a miscarriage.

Professor Kypros Nicolaides, who is regarded as the father of Fetal Medicine, says, "High risk and low risk patients should be identified and a woman should get the screening done by an expert so that invasive methods of taking out blood from the womb needn't be used. This is what can sometimes result in a miscarriage. An ultrasound is usually safe."

While Down's Syndrome screening is mandatory in the US, till such a law is made in India, women are advised to go in for tests at an earlier stage of pregnancy.