Pregnant women in Britain should soon get a more accurate and safer test for Down’s syndrome through the NHS in a bid to reduce miscarriage risk.
The test is backed by the UK National Screening Committee, who has said it would decrease anxiety in expectant mothers.
The move would prevent the need for invasive procedures, in which one in every 200 women experiences miscarriage.
The test will analyse tiny fragments of the baby’s DNA that end up in the mother’s bloodstream, to search for abnormalities. Down’s syndrome occurs when there is an additional copy of chromosome 21, which is the extra DNA from the baby that the test detects in the mother’s blood.
The NHS offers screening for Down’s syndrome 11 to 14 weeks into pregnancy and currently uses a combination of ultrasound scanning, the mother’s age and factors such as smoking to assess the probability of a baby having Down’s syndrome. Anybody with more than a 1 in 150 chance is offered an amniocentesis, which uses a needle to extract a sample of the fluid surrounding the foetus, known as amniotic fluid.
This procedure, however, carries a high risk and gives a negative result in the majority of cases. The new NIPT (non-invasive prenatal blood test) will be offered instead. If the test is positive, an amniocentesis will still be recommended, but the invasive procedure will not be necessary in the majority of cases.
Trials were conducted by Great Ormond Street Hospital to determine how the NIPT could be used by the NHS. The indication was that many women who would not have taken up the offer of an amniocentesis opted for the safer testing option. Trial leader Professor Lyn Chitty told reporters that many women are using the test to prepare for the birth of a baby with Down’s syndrome and support measures are in place for those with a positive diagnosis.
Director of programmes at the UK National Screening Committee believes the NIPT could potentially make a huge difference and that it will reduce anxiety for a high number of people and provide more accurate results.
It is still not clear how popular the test will be among women or how effective it will be in terms of other conditions such as Patau’s and Edwards’ syndromes, so it will be rolled out in a gradual manner. Estimates suggest, however, that between 3,000 and 5,000 amniocenteses will be rendered unnecessary every year.