December 9, 2010

Mother’s Blood Provides Genetic Info For Fetus

Scientists have found a new way to learn all there is to know about a fetus's genetic make-up by taking a sample of the pregnant mother's blood, according to a study released on Wednesday.

Before now, the most accurate way of screening a fetus for potential abnormalities has posed risks to the unborn child because they require doctors to take samples of fetal tissue by piercing the womb.

The techniques, which included amniocentisis and chorionic villus sampling, presented problems for expectant moms, especially among older women who want to be screened for chromosomal abnormalities that can become increasingly more prevalent with maternal age.

But according to Hong Kong researchers the entire fetal genome can be previewed by checking the mother's blood.

Fetal DNA makes up about one-tenth of a pregnant woman's blood plasma. Because fetal DNA molecules only exist in fragments in the maternal plasma, piecing together which ones belong to the fetus proved technically difficult.

Lead study author Dennis Lo and colleagues found in 1997 "floating" DNA from the fetus in the mother's blood, and labs have widely used the technique to test for gender as well as fetal genetic and chromosomal disorders.

However, such testing has been limited to one disease or genetic characteristic at a time.

The new research isolated fetal genetic signatures in the floating DNA, then compared its uniqueness against the genetic maps of the mother and father. Scientists were able to build a genome-wide genetic map of the fetus, which they could then scan for variations and mutations.

"Before the present work, it was not clear whether the entire fetal genome is represented in maternal plasma," wrote Lo. "This information is important because it demonstrates that a noninvasive genome-wide scan of the fetal genome from maternal plasma is possible."

Lo said the method of identifying nucleic acids in the plasma could also help in the fields of cancer diagnosis and tissue transplants.

"It would be interesting to investigate whether key features of the high-resolution size profile for circulating fetal DNA can also be seen in circulating tumor DNA and donor graft-derived DNA," the authors told AFP.

The researchers published their work in the US-based journal Science Translational Medicine.


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