Safer test for Down's syndrome

Scientists have developed a safer, less invasive test to detect chromosomal disorders such as Down's syndrome in unborn babies.

In a study of 18 women, researchers at the Howard Hughes Medical Institute found that testing a small amount of a pregnant woman's blood accurately detected Down's syndrome.

Because researchers know that a small amount of fetal DNA circulates in its mother's blood, they set out to determine if they could use a prenatal blood test to test for chromosomal abnormalities.

If the findings are confirmed in larger studies, it could mean the end of tests such as amniocentesis, which can induce miscarriage in a small number of cases.

"We need a larger clinical study to understand a bit more about the best way to implement (the test), but I am highly optimistic it will be used as a diagnostic test in short order," lead researcher Stephen R. Quake said in a statement.

Down's syndrome occurs when a baby has three copies of chromosome 21, rather than the usual two copies, and it causes physical and intellectual impairments.
Scientists diagnose Down's syndrome by testing amniotic fluid. The two procedures, amniocentesis and chorionic villi sampling, both involve putting a needle into the abdomen to withdraw the fluid.

The tests increase the risk of miscarriage by one per cent and are therefore limited to women who are at higher risk of having babies with chromosomal abnormalities, such as women over age 35.