麻豆传媒

A FAST test for genetic disorders means women could learn about the future health of their baby as early as 6 weeks into pregnancy.

The test for single-gene disorders, which are collectively more common than Down鈥檚 syndrome, could become available within five years. This would enable prospective parents to choose whether to proceed with a pregnancy if conditions like muscular dystrophy or Huntington鈥檚 disease are detected.

鈥淭his is just sensational 鈥� I鈥檓 completely blown away,鈥� says , a specialist in prenatal diagnosis at Royal North Shore Hospital in Sydney, Australia.

Many inherited diseases, including sickle cell anaemia, haemophilia and cystic fibrosis, are caused by mutations within a single gene. We know of 10,000 single-gene conditions and together, they affect about one in 100 births.

At the moment, options for prospective parents are limited. Embryos can be screened using pre-implantation genetic diagnosis (PGD), if couples opt for IVF. Those who conceive naturally can have tests like amniocentesis, but these carry a small risk of miscarriage, and detect a limited number of genetic disorders.

鈥淎bortion isn鈥檛 the only option. Test results could help reduce the effects of a genetic disorder鈥�

But the speed and ease of safer tests is improving. The non-invasive prenatal test (NIPT) for Down鈥檚 syndrome is available in over 60 countries, including the US and Australia, and it is being trialled in some UK hospitals. Now the team that developed NIPT has found a similar way to detect single-gene diseases.

The test, developed by at the Chinese University of Hong Kong, and her colleagues, can detect almost any single-gene disorder in the first 6 to 10 weeks of pregnancy. Guided by DNA from parent blood samples, the test looks for increases in the level of mutations associated with a particular condition in the mother鈥檚 blood once she is pregnant. In theory, any hospital pathology lab could run the test, producing results in one to two weeks.

In a study of pregnant women at risk of having a child with a single-gene disorder, the test accurately predicted the condition in all 12 fetuses whose DNA they were able to test (Clinical Chemistry, ).

In the UK, the has voiced concerns that NIPT for Down鈥檚 syndrome could lead to the number of babies born with the condition to decrease by more than 10 per cent. The group says this would have a long-term effect on the Down鈥檚 community, and will allow an informal kind of eugenics.

Informed choice

Advances in prenatal screening often spark controversy because of concerns that they might promote intolerance of diversity, McLennan says. 鈥淏ut this is not a negative eugenics campaign,鈥� he says. 鈥淭his is about choice. It鈥檚 about being given the opportunity to have information, to have appropriate counselling, and to make decisions.鈥�

鈥淪ome of the cystic fibrosis community are very against tests that are post-conception because they say 鈥榤y life is pretty good and I wouldn鈥檛 exist if that test was around when I was born鈥�,鈥� says Nettie Burke from Cystic Fibrosis Australia. 鈥淏ut there are mothers who have said to me 鈥業 wish I鈥檇 known, because I would have had an abortion鈥�.鈥�

But abortion isn鈥檛 the only option. In some cases, test results could help reduce the effects of a genetic disorder. Some of the symptoms of聽congenital adrenal hyperplasia, such as genital ambiguity, can be alleviated if a mother is given a steroid before 9 weeks of pregnancy. Thalassemia blood disorders can be treated with blood transfusions if given soon after birth. 鈥淚n the future, some disorders may also be treatable in utero using gene therapies,鈥� says Chiu.

The test will first be developed for couples with family histories of genetic disorders, but Chiu hopes it will later be incorporated into universal screening programmes. 鈥淭he potential for this is just phenomenal,鈥� says McLennan.

This article appeared in print under the headline 鈥淓arly fetal gene test鈥�