READING the whole genetic blueprint of a fetus long before birth could become a routine procedure thanks to a new blood test. As genetics increasingly informs prospective parents’ choices around conception, the test raises the prospect that it may soon become common to have an extensive understanding of a person’s genetic make-up before they are even born.
The new test can be carried out in the first trimester and gives an idea of a fetus’s genetic traits and future disease risks. The idea is to give people choice over whether to proceed with a pregnancy if the fetus has a genetic condition, but some fear it will lead to unnecessary abortions.
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The method works by isolating many types of fetal cell from a pregnant woman’s blood, and sequencing the DNA of those that look most intact. It was already possible to sequence fetal genomes with an existing prenatal testing technique, but this was a painstaking process and couldn’t be used routinely.
at the Beijing Genomics Institute in China and his team have used the new, easier method to sequence two fetal genomes. They found that one had gene variants associated with bowel cancer, liver disease and an intestinal disorder. The other had a gene variant linked to a (Prenatal Diagnosis, ).
“If you have genome data, you can give a child the best care from the very earliest stage”
The ability to identify such wide-ranging and subtle genetic information early in pregnancy could take parents into new philosophical ground. Many gene variants only increase disease risk by a small amount, but some can give a child a 1 in 5 chance of . At what risk level might a parent consider an abortion?
“What if a fetus has a gene associated with a 10 per cent risk of developing an intellectual disorder? Or ones that predispose them to heart conditions in later life?” asks at Murdoch Children’s Research Institute in Melbourne, Australia.
She doesn’t believe the technique should be used to scan entire fetal genomes. “I shudder thinking about people deciding to terminate a fetus based on a low probability that it might have something later in life.”
Some patient advocacy groups have previously raised concerns that prenatal testing will increase discrimination against people with genetic conditions – but others disagree. “We think that couples should have access to these technologies so that they can make the decision that’s right for them,” says .
Treatment in utero
Prenatal testing isn’t new. The chorionic villus sampling method has been in use since the 1980s, but it carries a risk of miscarriage so is usually only performed under certain circumstances, such as when there is a family history of a serious genetic disorder.
But family histories often aren’t enough to know if you could be a carrier for an inherited disease. of 12,000 women in Australia found that 1 in 20 were carriers of gene variants for either spinal muscular atrophy, fragile X syndrome or cystic fibrosis, and 88 per cent didn’t have a known family history of the conditions.
In the US and Australia, couples are now advised to undergo screening tests for some conditions before having children (see “I got DNA tested to see if I would pass on diseases to my kids”). Those at risk of having a child with a genetic disorder may choose to have IVF, so that they can pick an unaffected embryo.
The ability to screen a whole fetus’s genome is unlikely to change this approach. Although IVF can be a gruelling experience, discarding embryos will be preferable to selective abortions for many people, says at Victorian Clinical Genetic Services in Melbourne.
The ideal scenario will be if the technology is used to pick up things that can be corrected before birth, says at the Chinese University of Hong Kong. Researchers are already trialling in utero cell therapies for fetuses with brittle bone disease. CRISPR gene-editing, if proven safe, may offer more options.
Testing fetal genomes could also mean a newborn baby gets treatment right away. Some thalassemia blood disorders, for example, are best treated as soon after birth as possible. “If you have that knowledge, you can give the child the best paediatric care from the very earliest stage,” says Halliday.
Read more: I got DNA tested to see if I would pass on diseases to my kids
This article appeared in print under the headline “Birth of a new era”
