The test, known as coelocentesis, does not involve puncturing any of the membranes surrounding the foetus or the placenta, nor does it damage the blood vessels supplying it with oxygen and nutrients. Instead, a needle guided by ultrasound is introduced through the woman's vagina and fluid removed from the coelomic cavity, which surrounds the foetus in the first 12 weeks of pregnancy.
A preliminary study of 100 women at King's College Hospital achieved a 70 per cent success rate in obtaining a sample, with better results at 6 to 10 weeks than after 10 weeks, according to a report in The Lancet. The test is carried out under general anaesthetic. The women who agreed to take part in the trial were undergoing abortions for psychological reasons.
Conventional prenatal diagnostic testing includes amniocentesis, in which fluid from around the foetus is removed, and chorionic villus sampling (CVS) of the placenta. But amniocentesis is not usually carried out until 15-18 weeks, when a woman can feel foetal movement, and CVS, after 9.5 weeks, has been linked with limb abnormalities. Early amniocentesis is increasingly available, but has not been properly assessed and there are risks to foetal lung development.
The researchers, led by Professor Stuart Campbell, say that the risks of coelocentesis in women who are continuing their pregnancy have yet to be determined, but it has potential as an early prenatal test and may be safer than existing methods.