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Saturday, July 14, 2012

Using the mother’s blood to sequence her fetus’s genome

The decision as to whether to have a fetus tested for genetic disorders can be a difficult one. Some conditions can be treated more effectively immediately after or even before birth. On the other hand, current sequencing methods (amniocentesis and chorionic villi sampling) are not without their drawbacks. Ideally, doctors could determine a baby’s genome by taking a simple blood sample from the mother with no risk to the child. Well, that’s just what Jacob Kitzman from the University of Washington and his colleagues did.

The idea of using maternal blood to access information about her child is not new. About 10% of the cell-free DNA floating around a pregnant woman’s bloodstream is actually from her child. This information has been used to detect gross genetic abnormalities such as trisomies (having three copies of a chromosome rather than two). Trying to resolve an entire fetal genome is much trickier because you have to separate the mother’s DNA from the baby’s.

The researchers sequenced the genomes of a mother and father in a mother/father/fetus trio. They then got a mix of maternal and infant DNA from the mother’s plasma. By using the known sequences of the parents, they were able to deduce the baby’s genome. This was confirmed at birth when a sequence was obtained from the cord blood. Similar results were obtained for a second family trio.

The authors are the first to admit that this technique is only in its earliest stages. However, it’s not hard to imagine that any parents facing an at risk pregnancy, either due to family history or environmental factors, will one day wish to consider this noninvasive option.