London:
For the first time, scientists have succeeded in determining the entire genome of a foetus using only a blood sample from the to-be mother and a saliva swab from the father, a feat they say could lead to screening of unborn babies for more than 3,500 genetic disorders.
The genome scientists from the University of Washington, however, warned it would raise "many ethical questions" as the results could be used as a basis for abortion.
In the study, published in journal Science Translational Medicine, the scientists used a high-speed DNA sequencing method and some statistical and computational acrobatics to deduce the DNA sequence of the foetus.
They studied the blood sample DNA from the mother as well as DNA extracted from the father's saliva. Fitting pieces of the genetic jigsaw together, they were able to reconstruct the entire genome an unborn baby, the Daily Telegraph reported.
The researchers were then able to see what spontaneous genetic mutations had arisen. Such mutations, called "de novo" mutations, are responsible for majority of genetic defects.
By checking their prediction of the baby's genetic code with actual DNA taken after the birth, they could identify 39 of 44 such mutations in the baby boy. The team also tested their approach on the woman who was earlier in 18 weeks of her pregnancy, and found it still worked.
Lead study author Dr Jay Shendure said: "This work opens up the possibility that we will be able to scan the whole genome of the foetus for more than 3,000 single-gene disorders through a single, non-invasive test."
"The improved resolution 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," added co-author Jacob Kitzman.
In future, the scientists hoped, a more refined and less costly version of the procedure could make pre-natal genetic testing far more comprehensive than it is now. Currently, it involves inserting a probe into the womb to take fluid from the foetal sac or placental samples.
Existing methods only enable doctors to check for a small number of genetic disorders, which include Down's syndrome and cystic fibrosis, muscular dystrophy and spina bifada.
But the scientists said their test could give a wealth of information on the baby's future health by predicting for over 3,500 genetic defects.
However, the researchers feared that the work would give rise to abortions. "The less tangible implication of incorporating this level of information into pre-natal decision-making raises many ethical questions that must be considered carefully within the scientific community and on a societal level," they warned.
"As in other areas of clinical genetics, our capacity to generate data is outstripping our ability to interpret it in ways that are useful to physicians and patients," they added.
Josephine Quintavalle, founder of the Pro-Life Alliance, said: "Whilst this new test may not itself be invasive, given our past track record, it is difficult to imagine that this new test will not lead to more abortions," she said.