New Era Near For Fetal Screening?

A new study in the Journal of the American Medical Association shows the potential to diagnose genetic disorders in a developing fetus non-invasively, with a test of the mother's blood.

March of Dimes Medical Director Nancy Green calls this an exciting advance that will lead to new testing that will reduce the risks to the fetus from more invasive procedures, such as amniocentesis.

She explains to The Early Show co-anchor Rene Syler that there are many non-invasive screening tests available during pregnancy to indicate the possible presence of a problem and help doctors and parents better manage the course of the pregnancy.

But obtaining a firm diagnosis of a specific disease or disorder often involves invasive procedures to obtain samples of amniotic fluid, cord blood, and fetal cells. These tests routinely provide expectant parents and their doctors with a look at the genetic and chromosomal makeup of the fetus, and genetic abnormalities and disease diagnosis is possible using these techniques.

Although there is a simple blood test currently available for predicting the probability for neural tube birth defects or Down Syndrome, there is no way to diagnose many genetic problems without invasive procedures such as amniocentesis. It and other invasive prenatal testing come with a small but significant risk of complications as severe as miscarriage.

But this week's Journal of the American Medical Association describes a new technique to help detect fetal genetic disorders non-invasively. A blood test called "size-fractionation" was done on samples of the mother's blood and enabled researchers to separate and identify the fetal DNA, and through it, determine the risk for the genetic blood disorders known collectively as beta-thalassemia.

Researchers in Switzerland analyzed samples from 32 at-risk women ten to twelve weeks into their pregnancies. They were able to correctly determine whether the gene mutation used for diagnosis of beta-thalassemia was present from the fetal DNA in 80 to 100 percent of the cases, with only one false-positive test.

The researchers say the study proves that fetal genetic traits can be detected from the analysis of fetal DNA in the mother's blood, and add that the blood test is relatively simple and cost-effective.

Green points out that many parents elect to screen their unborn babies for birth defects and genetic disorders, especially those at high risk because of the family history of disease. She says this latest research is an exciting development because it provides very real hope for expanding the available technology for much more rapid screening and diagnosis for genetic disorders, defects and disease. It could also mean the information will also be accessible at a much earlier stage of pregnancy.

The use of a simple and cheap blood test using the mother's blood instead of amniotic fluid or cord blood or fetal tissue also provides a way to leave a normally-progressing pregnancy undisturbed. For many parents, the risks of amniocentesis make the procedure and other invasive procedures a stressful and worrying experience. If women can avoid the need for an invasive amniocentesis to obtain this kind of information, more women might elect to have tests done.

The new research adds to the evidence that there are plenty of fetal cells and fetal DNA in the mother's blood, and the ability to separate the fetal material opens up the door to a wide range of screening as our understanding of genetics progresses and more genetic causes of disease are discovered.

Dr. Green says it is very important for prospective parents to be aware of the various methods that are available for screening for serious or potentially-lethal genetic disorders. Along with amniocentesis, there are already other, easier methods, such as ultrasound and blood tests, to screen for common birth defects and genetic disorders.

Whenever possible, she says, it's important for parents to think about family history of disease before pregnancy and determine with their doctor what kinds of pre-screening might be appropriate.