New research shows how blood from the expectant mother and saliva from the father are enough to safely sequence the whole fetal genome.

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PROBLEM: Though scientists have long known that a pregnant woman's blood plasma contains cell-free DNA from her developing fetus, they've had trouble figuring out which genetic variants get passed on from mother to child. As a result, doctors have had to resort to invasive procedures, such as tapping the protective fluid sac in the mother's womb, to detect suspected abnormalities.

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METHODOLOGY: Geneticists led by Jacob O. Kitzman used saliva specimens from expectant fathers and blood samples from mothers who were about 18 weeks pregnant. To non-invasively determine the whole genome sequence of the fetuses, they used advanced biostatistics to combine the genome sequencing of the parents, genome-wide maternal haplotyping (grouping of genetic variants), and deep sequencing of maternal plasma DNA. They then checked the accuracy of their genetic predictions by collecting umbilical cord blood at birth.

RESULTS: The researchers successfully picked out the parts of the fetal genetic material inherited from each parent with over 98 percent accuracy. They also detected 39 of 44 new genetic variations not shared with either parent.

CONCLUSION: Parental DNA samples -- blood from the mother, saliva from the father -- contain enough genetic information to map a fetus' genome.

IMPLICATION: A safe, affordable, and comprehensive genetic screen during pregnancy for thousands of potential conditions may be in the offing. As co-author Jay Shendure puts it in a statement: "This work opens up the possibility that we will be able to scan the whole genome of the fetus for more than 3,000 single-gene disorders through a single, non-invasive test."

SOURCE: The full study, "Noninvasive Whole-Genome Sequencing of a Human Fetus," is published in the journal Science Translational Medicine.