Expectant mothers are used to fuzzy images on ultrasound monitors and blood tests to screen for potential health problems in their unborn babies. But what if one of those blood tests came back with a readout of the baby's entire genome? What if a simple test gave parents every nuance of a baby's genetic makeup before birth?

Recent studies show that it's possible to decode an entire fetal genome from a sample of the mother's blood (see "Using Parents' Blood to Decode the Genome of a Fetus"). In the future, doctors may be able to divine a wealth of information about genetic diseases or other characteristics of a fetus from the pregnant mother's blood. Such tests will raise ethical questions about how to act on such information. But they could also lead to research on treating diseases before birth, and leave parents and their doctors better prepared to care for babies after birth.

It's been about 15 years since Dennis Lo, a chemical pathologist at the Chinese University of Hong Kong, first discovered that fragments of DNA from a fetus could be found in a pregnant woman's blood. The work was a breakthrough, since obtaining fetal DNA from the amniotic fluid, placenta, or directly from the fetus's blood requires an invasive procedure and carries a risk of miscarriage. A noninvasive test would make genetic testing safer and much more widely accessible.