Sequencing the whole genome of a fetus could provide a medical early warning on a previously unknown scale - but it also brings dilemmas, says Harriet A. Washington
BOY or girl? This you can easily discover, but wouldn't you like to know more? If you could peer into your baby's medical future, what traits would you most want assurance about?
Most parents wouldn't hesitate: a healthy child. Soon science will be able to help them with that more quickly, completely - and safely - than ever before.
In June, a team at the University of Washington in Seattle announced a new technique that enables the construction of a comprehensive genome sequence - a genetic "blueprint", as they described it - of the developing fetus from as early as the first trimester (Science Translational Medicine, vol 4, p 137ra76). The test could be available in clinics in as little as five years.
Then, in July, a team at Stanford University in California announced a slightly different technique for obtaining the same information (Nature, vol 487, p 320).
Both techniques rely on the fact that fetal DNA circulates in the mother's bloodstream and can be isolated and sequenced. The Seattle test needs only a sample of saliva or blood from the father and blood from the mother. After determining the parents' genomes, it is possible to discern which DNA comes from the fetus. The Stanford test requires only maternal blood.
Both tests are non-invasive, thus avoiding the 2 per cent risk of miscarriage posed by today's most common antenatal genetic tests, amniocentesis and chorionic villus sampling. These require a needle to be inserted into the amniotic sac so that the fetal DNA can be tested for Down's syndrome and other genetic disorders.
The existing antenatal tests can also spot other chromosomal abnormalities, including cystic fibrosis, trisomy 13, and Turner, Klinefelter and fragile-X syndromes. In contrast, the genetic blueprint can finger thousands of potentially problematic genes. It is "like going from being able to see that two books are stuck together to being able to notice one word misspelled on a page", says Jacob Kitzman, a member of the University of Washington team.
The benefit is a medical early warning on a previously unknown scale. Children with the genetic disorder phenylketonuria, for example, are usually diagnosed after birth and must be put on a strict, lifelong diet. Knowing the child's status beforehand would be helpful.
Given this and other potential benefits, should we not hasten to make blueprint screening mandatory, as many newborn tests are today? Not until we know more, and maybe not even then.
Read the original:
A genetic blueprint of your unborn baby