Experimental Prenatal Test Helps Spot Birth Defects

By Amanda Gardner
HealthDay Reporter
Friday, February 2, 2007; 12:00 AM

FRIDAY, Feb. 2 (HealthDay News) -- A new, noninvasive method of prenatal testing may one day help to detect birth defects in unborn babies.

But it'll be a while before the technique comes to market.

"We've shown the first abnormality, and this is proof of principle to show that this technology can be a noninvasive test from maternal blood," said study author Dr. Ravinder Dhallan, founder and chief executive officer of Ravgen Inc., in Columbia, Md. "Next, we will do a larger study and start building the infrastructure to go to market."

Dhallan wouldn't speculate on when such a test might become commercially available, saying only, "We don't intend to rush it. The health of a baby is the most important thing in anyone's life, but we are moving with deliberate speed."

Dr. Michael Katz, senior vice president for research and global programs at the March of Dimes, called the experimental test a "good system if it can be sustained by more extensive tests. It also dovetails with the current suggestion by the American College of Obstetricians and Gynecologists that prenatal diagnosis should be applied to all women."

The study findings are published online Feb. 2 inThe Lancet.

Currently, tests to detect chromosomal abnormalities before a baby is born pose a number of problems.

Ultrasound is noninvasive but does require subsequent invasive testing before a final diagnosis can be made. And invasive diagnostic tests, such as amniocentesis and chorionic villus sampling, can pose risks to the pregnancy, including miscarriage.

"Even though the current invasive tests are quite safe, relatively speaking, they are invasive, and there are complications," Katz said. "Moreover, they have to be done somewhat later [in the pregnancy], and the sooner one makes this diagnosis, the better."

Scientists have known for several decades that fetal cells are present in the mother's blood as early as five weeks into the pregnancy. The problem is that the cells are extremely rare, representing only about one in a million of total cells.

The reason for their rarity? The mother's cells are very much like water balloons: From the moment blood is drawn, her cells burst and let loose maternal DNA into the blood stream. This serves to dilute the fetal DNA, Dhallan explained.

"Every time a mother's cell bursts, it dilutes the fetal DNA, particularly when you transport samples and when you centrifuge and process samples to get the DNA out of the plasma," he said.

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