The screening procedure, which is said to be little more than a cervical smear, involves washing foetal cells from the top of the cervix where it forms the entrance to the womb.
Doctors have been searching for years for a non-invasive screen for Down's syndrome and other chromosomal abnormalities. Current tests have drawbacks: they are performed late in pregnancy, causing the woman more distress if a termination follows; in a small proportion of cases the tests cause spontaneous abortions; and one test has been linked to limb deformities. Another test indicates which women are at risk of a having a Down's baby.
The new test is done either by washing the cervix with a sterile saline solution and drawing the fluid back into a syringe, or even more simply by gently collecting cells from the cervical channel by aspiration.
Matteo Adinolfi, Professor of Developmental Immunology and Genetics at Guy's and St Thomas's medical school, says in the Lancet: 'The technique is sufficiently non-invasive for use in an ante-natal clinic without analgesia (pain relief) or ultrasound guidance.'
Professor Adinolfi and Dr Peter Soothill, consultant in foetal medicine at University College London Medical School and Great Ormond Street hospital, tested the method on 12 women who were about to have terminations. 'For 10 years, researchers have been trying to find enough foetal cells in maternal blood. It is possible but it is very difficult and the equipment needed is very expensive,' Professor Adinolfi said.
The new method produces many more foetal cells which can be isolated and their nuclei visualised from abnormalities in the chromosomes, using proved laboratory techniques. It is carried out between the eighth and thirteenth week of pregnancy.
While the Lancet report says the cervix was washed with saline solution, Professor Adinolfi said in recent weeks they had refined the method and could gather enough foetal cells from mucus in the cervix alone.
Dr Soothill said the method was less invasive than chorionic villus sampling (CVS), one test for Down's and other abnormalities, in which a hollow tube is passed through the cervix and into the uterus to collect cells that surround the foetal sack.
'We think the method is safer, easier and probably quicker. We don't need to go into the uterus. My dream is that every woman would have this when she attends the hospital for the first time,' he said. He emphasised that the safety of the method has not yet been tested. They also want to establish the optimum week of pregnancy for conducting the test.
Dr Soothill said the next stage was planned. Women who are having CVS will be asked if they will permit the cervical washing procedure first.
The risk of having a Down's baby increases with the age of the mother. Amniocentesis, when a sample of amniotic fluid is taken for analysis, is offered to women over 36.
In July, a working party of the Royal College of Obstetricians and Gynaecologists recommended that health authorities should offer a different test to all women to show who is at risk. This test is not diagnostic and can only indicate which women should be given amniocentesis.
The cervical washing technique could mean that all pregnant women could be told they had a foetus with Down's before the 12th week.Reuse content