Karnataka has second-highest marriages among blood relatives

Percentage of consanguineous marriages in states/UTs

Karnataka has the second-highest percentage of women aged 15-49 who have consanguineous marriages, shows the National Family Health Survey-5 whose report was released on Friday.

Around 27% of women in the state were found married off to close relatives such as cousins, uncles and brothers-in-law.

Tamil Nadu saw most such marriages at 28%. The national average is far lower at 11%.

A break-up of those consanguineous marriages in Karnataka shows that 9.6% of the women were married to the first cousin on the father's side, 13.9% were married to the first cousin on the mother's side, 0.5% to the second cousin, 0.2% to the uncle, 2.5% to other blood relatives and 0.1% to the brother-in-law.

Genetic disorders can be dominant or recessive, and consanguinity in parents increases the risk of recessive disorders in children born to such couples.

Dr Kruti Varshney, Consultant Clinical Geneticist at the Centre for Human Genetics (CHG), Bengaluru, said: "Most of the marriages (of patients' parents) that we see are uncle-niece or first-cousin marriages. This definitely increases the risk in children of general birth defects and genetic problems. Most of them are recessive in nature."

She continued: "The most common disorder is thalassemia. Then comes spinal muscular atrophy, which is a recessive disorder and happens because both parents are carrying the same mutant alleles on one copy of the gene which then passes on to the child in double dose. That's a one-in-a-four chance."

Dr Meenakshi Bhat, associate director of CHG and visiting consultant geneticist at the Bangalore Fetal Medicine Centre, said: "In about 5% of the consanguineous couples, if there is a common gene running through the mother and the father because of a common ancestor, the child may inherit a genetic disorder which is autosomal recessive."

If a family has one child with a recessive disorder, doctors advise couples to go for prenatal testing for subsequent pregnancies. At least 50% to 60% of the patients that come to CHG with a genetic problem have parents with a history of consanguinity, she explained.

"We do get 2-3% of couples who are educated and who come before marriage and ask us what to do if their families have arranged such marriages. We counsel them and ask them if it is possible to find other partners. In other countries, such to-be couples are screened for the most common disorders that they can carry," she added.

Dr Karthik Nagesh, Chairman and HoD, Neonatology, Manipal Group of Hospitals, is currently treating three children, all of whom have a history of consanguinity. Two of them have neurological problems but one has a heart problem. One of their mothers had babies who previously died and the subsequent child has a genetic problem.

"Our genetics department counsels such parents for any subsequent pregnancies and similar marriages that the family may be planning in their near relatives," he said.