Oct 17, 2008 7:09 pm US/Eastern
HealthWatch: Fetal Screening For Genetic Defects
NEW YORK (CBS) ―
Parents-to-be could soon have an easy, safe way to test their baby for genetic defects.
It's a newly developed blood test that's simple and can also be performed during the early stages of pregnancy.
It's a difficult decision for many expecting parents – whether or not to test for genetic defects.
"Just the thought of a long needle going through the belly and having to actually pierce the placenta was very nerve-wracking for us because we tried for a long time to have a baby," Teri Theuriet said.
Prenatal testing for disorders like Down Syndrome can be invasive, and carries some risks.
During a medical procedure called amniocentesis, a needle draws fluid from the placenta, slightly increasing the chance of miscarriage.
But researchers at Stanford University have developed a new test that eliminates the risk.
"There has been a decade-long search for a non-invasive test for Down Syndrome, and I think we've taught the world how to do it now," Dr Stephen Quake, one of those researchers, said.
Doctors draw a few tablespoons of blood from the mother.
"That gives us a window into the genetics of the baby," Quake said.
Using a computer, doctors find DNA fragments of the fetus in the mother's blood, and then match the DNA to chromosomes.
The presence of too many copies of any one chromosome is a red flag. Down Syndrome, for example, involves an extra copy of chromosome 21.
Because fetal DNA shows up in the mother's blood in the first weeks of pregnancy, the new test can be done at about five weeks.
That's much earlier than current testing, which happens at around four months.
Mom-to-be Theuriet says she would have made a different decision if the test was available earlier in her pregnancy.
"If it was just a blood test, absolutely, we would have done it," Theuriet said.
Traditional methods of screening for Down Syndrome are strongly recommended for mothers over age 35.
Researchers hope that the new test is as accurate as the traditional test, and that it can encourage younger mothers to be screened. They aim to make it available within a few years.
Down Syndrome is related to the mother's age. For mothers over age 45, one out of every 19 babies conceived has the illness.
(© MMIX, CBS Broadcasting Inc. All Rights Reserved.)
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