Parents may soon be able to find out if their unborn child is prone to any inherited diseases, researchers said on Thursday, after developing a non-invasive technique to draw the entire gene map of the human fetus. By analyzing a sample of the mother’s blood, which contains DNA from the fetus, scientists in Hong Kong and the United States were able to identify all the DNA strands that belong to the child and piece them together.

“Before this work, people only could look for one disease at one time but now you can construct a screen for a number of diseases which are prevalent in any particular population,” said lead author Dennis Lo, professor of medicine from the Chinese University in Hong Kong.

The research team’s breakthrough was discovering that the mother’s plasma holds the entire foetal genome. Previously, only part of the baby’s DNA was thought to be in the mother’s blood.

“Now that we know (the) entire foetal genome is in there, you can look for any disease that is genetically inherited.”

The study, published in the journal Science Translational Medicine on Thursday, recruited a couple undergoing prenatal diagnosis for a hereditary blood disorder, beta-thalassemia.

“In the mother’s blood, 90 percent of the DNA is her own ... and 10 percent is the baby’s. Half of the foetal genome is from father and half from mother,” Lo said.

The team found the fetus inherited a beta-thalassemia mutant gene from the father, meaning the baby was a carrier of the disease. Lo described the process as akin to putting together a jigsaw puzzle with millions of pieces - only in this case, 10 times as many pieces from a much larger jigsaw were mixed in with it too. “The whole genome is fragmented into millions of pieces and by this exercise, we assemble it back,” Lo said. “It’s like assembling a jigsaw puzzle with millions of pieces. But to make it more challenging, you mix in 10 times (the number of pieces) from another jigsaw puzzle, that’s the mother’s own DNA. And you are trying to assemble the child’s.”

Experts who were not involved in the study called for caution. “It is too early to apply the technology widely as we are not yet able to interpret many of the results that can be generated accurately,” said Christine Patch, chair of the British Society for Human Genetics.

“We do not randomly test pregnancies for a long list of ... conditions that may only manifest in adult life on the basis that individuals may not want to know that information when they are older.”

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(Reuters)