Couples, with a child having a genetic disease, would have second thoughts about conceiving another child, fearing that the latter would also have the same disease.
However, new techniques in prenatal genetic diagnosis have brought a ray of hope for these couples.
According to reports, at least 70 million Indians suffer from one of 7,000 rare diseases. Most of these disorders are genetic in nature, and many who suffer do not live beyond the age of five.
Genetic counselling can confirm or rule out a suspected condition in a foetus, said Meenakshi Bhat, professor at the Centre for Human Genetics, Bengaluru.
“Prenatal diagnosis can be used for couples for carriers of disorders such as Hunter Syndrome. A tissue from the unborn foetus is tested, usually within 12 weeks of pregnancy,” said Dr. Bhat. Testing of the foetus is done through amniocentesis: DNA is extracted from the amniotic sac which is then “read” for genetic defects.
A more recent technique, which has just begun in India, is non-invasive prenatal testing (NIPT).
“In NIPT, blood is drawn from the mother and foetal DNA is read from the blood, as some amount of foetal DNA (10 to 11%) leaks into the mother’s blood,” says Vijay Chandru, Director, Centre for Health Ecologies and Technology. “It has just started in India, and in the West they no longer do amniocentesis as there is a 1 to 2% risk of losing the foetus,” said Dr. Chandru.
Knowing that a foetus is predisposed to a particular genetic disorder poses ethical questions to the parents.
“It is a difficult decision for parents to make: whether to go ahead with the pregnancy or not. Prenatal genetic screening gives them the chance to make an informed choice,” said Dr. Chandru adding that counselling would be an important aspect of communication of test results.
Another experimental technique, pre-implantation genetic diagnosis, tests DNA from embryo cells before the foetus is formed.
Dr. Bhat said that this has not been tried till now in Karnataka and the success rate was just 30% in top centres across the world, due to associated difficulties.
“You are testing DNA from a single cell, so the accuracy needs to be good. On paper it’s technically an easy thing to do, but it calls for high expertise from the practitioner,” she explained.
