For the first time,researchers have determined virtually the entire genome of a foetus using only a blood sample from the pregnant woman and a saliva specimen from the father.
The accomplishment heralds an era in which parents might find it easier to know the complete DNA blueprint of a child months before it is born.
That would allow thousands of genetic diseases to be detected prenatally. However,the ability to know so much about an unborn child is likely to raise serious ethical considerations as well. It could increase abortions for reasons that have little to do with medical issues and more to do with parental preferences for traits in children.
Its an extraordinary piece of technology,really quite remarkable, said Peter Benn,professor of genetics and developmental biology at the University of Connecticut, not involved in the work.
The paper,published on Wednesday in the journal Science Translational Medicine,was written by genome scientists at University of Washington. They took advantage of new high-speed DNA sequencing and some statistical and computational acrobatics to deduce the DNA sequence of the foetus with about 98 percent accuracy.
The process is not practical,affordable or accurate enough for use now, experts said. The University of Washington researchers estimated that it would cost $20,000 to $50,000 to do one fetal genome today.
However,the cost of DNA sequencing is falling at a blistering pace,and accuracy is improving as well. The researchers estimated that the procedure could be widely available in three to five years. Others said it would take somewhat longer.
If this sort of thing is ever to be used on a widespread basis,I think it necessarily has to be non-invasive, said Jay Shendure,associate professor of genome sciences at University of Washington,who supervised the research team.
The genome was determined from blood samples taken 18.5 weeks into the pregnancy,although the researchers said the technique could probably be applied in the first trimester,as early or even earlier than some invasive techniques.
Such information would allow detection of so-called Mendelian disorders,like cystic fibrosis,Tay-Sachs disease and Marfan syndrome,caused by mutations in a single gene. More than 3,000 such diseases collectively occur in about 1 percent of births. The mutations can be inherited from the parents or they can arise spontaneously in the foetus.