OUR knowledge of the genetics of the unborn child has taken a big step forward.
A risk-free test for Down鈥檚 syndrome is now a realistic prospect, thanks to technology that allows us to analyse traces of fetal RNA and DNA in maternal blood (see 鈥淏lood tests could eliminate Down鈥檚 miscarriage risk鈥�). Eventually many abnormalities could be spotted at 10 weeks, or even earlier, without risk of miscarriage.
The blood test is safe enough to be used for screening, rather than just for those at risk. Some are likely to protest that there will be more abortions. But let鈥檚 not forget about the parents. Existing tests are medieval. They involve extracting fluid or tissue from the womb, which is frightening for good reason: amniocentesis and chorionic villus sampling (CVS) carry around a 1 per cent chance of miscarriage. If the blood tests prove reliable, the cut in miscarriages could be as significant as the rise in terminations. Most importantly, they will offer more parents a choice, and one that is not complicated by hazardous tests.
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The safer tests are not ready yet, though. CVS or amniocentesis can only be replaced after much bigger trials have shown these tests pass muster in terms of accuracy, specificity and affordability. Even if they do pass, their safety must not mean counselling for parents is deemed less necessary.
This news is long overdue. Back in the 1960s, researchers sought that one fetal cell in 10 million or so maternal blood cells that could be used for a safe diagnosis. We can now hope to see a kinder era in prenatal testing.
Genetics 鈥� Keep up with the pace in our continually updated special report.
