Scientists have successfully sequenced a baby's entire genome while it was still in the womb — and without interfering with its protective sac. This non-invasive breakthrough could have profound implications for prenatal screening practices, and the potential elimination of genetic disorders.
Scientists working at the University of Washington took maternal blood samples 18 weeks into a pregnancy, along with a saliva specimen from the father. This supplied enough genetic information for the researchers to map the fetus' DNA. The researchers later checked the accuracy of their results by using umbilical cord blood collected at birth.
It's been known for a while that a pregnant woman's blood plasma contains cell-free DNA from her developing fetus. It rises during gestation, but disappears after the baby is born. Women typically have about 10% of the cell-free DNA from their baby in their blood plasma during a pregnancy. By using a recent breakthrough in statistical modeling and other technical advances, the research team was able to assess subtle variations in the fetus' genome, down to very small, one-letter changes in the DNA code.
The study, which was led by Jay Shendure, associate professor of genome sciences, is poised to have a significant impact on the way that prenatal screening is done. The findings were reported in the June 6 issue of Science Translational Medicine, a journal of the American Association for the Advancement of Science.
Bioethical implications emerge
Shendure's team suggests that the new technique could help prospective parents detect severe genetic abnormalities in their unborn children. The tests, say the researchers, is far safer than the more invasive sampling of fluid from the uterus, which a common procedure in obstetrical practice. The technique could help fertility doctors detect such disorders as Down syndrome, cystic fibrosis, and Tay-Sachs disease.
An overarching ethical question that emerges is whether or not the technique should be used to screen for other less severe genetic abnormalities. Scientists are increasingly discovering the genetic markers for such conditions as autism, epilepsy, schizophrenia, and intellectual impairments. Armed with the information that an unborn baby has one of these conditions, some parents may opt to abort the fetus. Looking even further ahead, some parents may also wish to use the practice for trait selection purposes, choosing such genetically-determined characteristics as personality disposition, intelligence, and hair and eye color.
Critics of human trait selection contend that families who practice selective abortion ignore the fact that many children born with such conditions go on to lead relatively normal lives. Other critics worry about the imposition of neurotypicality and the unnecessary stigmatization of such conditions as autism and schizophrenia.
Supporters of human trait selection argue that this is an issue of reproductive liberty, and that parents reserve the right to make such decisions for their families. Others contend that parents have a duty to ensure that they bring healthy children into the world given the choice.
Like most innovations, it takes time for the dust to settle before society and individuals know exactly how to move forward. This breakthrough is no exception.
Eurekalert. Image via Shutterstock / Sashkin.