Pregnancy blood test for Down's syndrome developed

Published on Sunday 6 March 2011 15:09

Pregnant women may soon be able to have a blood test to predict whether their baby is likely to have Down's syndrome instead of undergoing risky invasive tests, scientists said last night.

In a study published in the Nature Medicine journal, researchers from Cyprus said a trial on 40 pregnancies using the test, which involves analysing the woman's blood to detect DNA differences between the mother and the foetus, showed it accurately predicted which foetuses were at risk of developing the syndrome.

Philippos Patsalis, medical director of the Cyprus Institute of Neurology and Genetics, who led the study, said the results were "very exciting"

He added that the test now needed to be trialled in a larger study of about 1,000 pregnancies, but could lead to changes in clinical practice within two years.

"We believe we can modify this test and make it much easier and simple… (and then] we can have something ready to be introduced into the clinic," he said.

Down's syndrome is the most common genetic cause of learning difficulties, occurring in one in 700 live births worldwide.

The risk of having a baby with Down's - which occurs when a child has three copies of chromosome 21 instead of the normal two - increases sharply in older mothers. The risk for a 40-year-old mother is 16 times that for one who is 25.

Doctors currently use a test known as amniocentesis to check whether a baby is likely to be born with Down's. This is generally done at about 15 or 16 weeks' gestation and involves taking amniotic fluid by inserting a hollow needle into the uterus.

Since amniocentesis carries a small risk of spontaneous miscarriage, scientists have been looking for less invasive ways to test for Down's and other potential genetic problems.

Dr Patsalis' method takes advantage of differences in the DNA methylation patterns - which are important to control levels of genes - between mother and foetus.

It involves detecting extra copies of chromosome 21 in the foetus by analysing the mother's blood.