June 6, 2012 -- Samples of blood and saliva from parents-to-be may help identify thousands of genetic disorders in fetuses soon after conception without invasive testing, researchers say.
In a study published today in the journal Science Translational Medicine, researchers from the University of Washington report that they were able to determine the complete DNA sequence of two babies in the womb by analyzing blood samples from the mother and saliva samples from the father.
Genetic predictions were confirmed once the babies were born by analyzing umbilical cord blood collected at birth.
The test is not ready for use yet. Although cost and technological challenges remain, the research could lead to a simple non-invasive test to identify more than 3,000 disorders caused by single-gene mutations, says study co-author Jay Shendure, MD, PhD.
"Many of these diseases are so rare that most people have never heard of them, but collectively they affect around 1% of births," Shendure tells WebMD.
Fetal DNA in Mom's Blood
Only a few genetic disorders, including Down syndrome, are screened for during pregnancy. They use invasive and potentially risky procedures such as amniocentesis and chorionic villus sampling.
The search is underway for less invasive tests using blood samples from pregnant women instead of fluid from the uterus. That's based on the recognition that fetal DNA is present in the blood of pregnant women at varying concentrations during pregnancy.
In the newly published study, researchers confirmed that blood taken from an expectant mother about 18 weeks into her pregnancy and saliva specimens taken from the father contained enough genetic information to map the DNA code of the developing fetus.
The finding was later confirmed in another expectant couple with blood taken from the mother even earlier in her pregnancy.
Doctoral candidate Jacob Kitzman, who led the study, says the researchers were able to identify new mutations in fetuses not shared with either parent.
Because these mutations are the cause of many genetic disorders, searching for them is critical for a comprehensive test, Kitzman tells WebMD.
Interpreting Data Remains a Challenge
Mutations have been linked to more complex disorders influenced by genes, including autism, epilepsy, and schizophrenia. But it remains to be seen if fetal DNA mapping will be useful for assessing a baby's risk for these and other disorders in a clinical setting.
However, the capacity to collect data by mapping an unborn baby's DNA has outpaced medical science's ability to interpret the data in ways that are useful to doctors and patients, Shendure points out.
"Although the noninvasive prediction of a fetal genome is now technically feasible, its interpretation ... will remain an enormous challenge," he noted in a news statement.
Pediatrician and genetic disease specialist Arthur Beaudet, MD, agrees. He is professor and chair of the department of molecular and human genetics at Baylor College of Medicine in Houston. Beaudet did not work on the new test.
"We are increasingly going to have this kind of genetic information about ourselves and our children and even our unborn children," he tells WebMD, adding that as the cost of gene sequencing drops the research should lead to better, cheaper, and less invasive tests to identify genetic disease risk early in pregnancy.