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Health & Pregnancy

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New Earlier, Noninvasive Paternity Test Developed

Experts Say the Test Has Important Medical, Legal Applications

Finding Fetal DNA in Mom's Blood continued...

The first is that while researchers have long known that fetal DNA is present in the mother's blood, they believed it was floating around in such tiny amounts that it was almost impossible to find and analyze.

One of the reasons it was thought to be so rare, says researcher Ravinder Dhallan, MD, PhD, chairman and chief executive of Ravgen Diagnostics in Columbia, Md., is that the mother's blood cells easily burst when blood samples are drawn, which dilutes the fetal DNA.

By mixing a fixative agent into the blood sample, Dhallan says he was able to isolate enough fetal DNA so that it could be tested.

"What we realized was that if you add any fixative, it makes the mother's white blood cells, instead of being like water balloons that easily burst, they become more like ping pong balls that are stiff and won't burst," says Dhallan. "Now you've got 25% fetal DNA instead of 1% fetal DNA" in the blood.

By looking at the baby's DNA, researchers are able to spot places where the gene sequences are different from the mother's by only one letter. That letter will match the father's DNA. A sample of DNA from a suspected father can then confirm or exclude paternity.

When researchers tested 30 blood samples from biologic mothers and fathers who were grouped with unrelated men, they say they were able to correctly identify paternity in every case.

According to Ravgen's web site, the technology was used in 2009 to help prove that Michael A. Roseboro, who was on trial for his wife's murder, had fathered a baby with another woman. Prosecutors argued that the affair was motive for the murder.

Dhallen says he was motivated to develop the paternity test after being contacted by women who were eager to prove paternity and uncertain about whether to continue their pregnancies after situations involving violence, including rape.

"There are so many situations where people need to identify the paternity before the baby is born that are social, medical, and legal," he says.

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