Experts back maternal blood test for Down's syndrome

A test using a simple blood sample from the expectant mother should soon be the primary screening method for Down's syndrome, according to a report from the Royal College of Obstetricians and Gynaecologists (RCOG).

The test, which is already available privately, has been described as 99 percent accurate and carries no risk to mother or child.

Speaking to the Telegraph, Professor Peter Soothill, consultant in fetal medicine at University Hospitals Bristol NHS Foundation Trust and a co-author of the report, described it as 'the most exciting development in pregnancy care in many years'.

In the UK about 750 babies a year are born with Down's syndrome, which is caused by an extra copy of chromosome 21.

Current screening for Down's syndrome takes the form of an ultrasound and a maternal blood test (the 'combined test') which are used to estimate risk of the condition. In at-risk cases, this can be followed by diagnostic tests which require the insertion of a needle into the uterus, a process which carries a one percent risk of miscarriage.

The new test, referred to as non-invasive prenatal testing (NIPT), relies on fragments of DNA from the fetus which can be detected in the mother's blood.

The test can also detect other chromosomal abnormalities, such as the rare conditions Edwards' syndrome and Patau's syndrome.

The report states that the test could be included either as an alternative to invasive diagnostic tests in at-risk cases, as a part of the combined test, or as a primary screen, replacing the combined test. In both the USA and Canada NIPT has so far been recommended only in at-risk cases, with Canadian guidance adding that a positive test should be confirmed by amniocentesis before termination of the pregnancy.

The UK National Screening Committee is currently trialling the technology at Great Ormond Street Hospital for Children in London (reported in BioNews 729), and is expected to make a decision next year on whether to offer the test on the NHS.

The chair of the RCOG's scientific advisory committee, Dr Sadaf Ghaem-Maghami, said the new technology's potential was 'exciting' but stressed the continued importance of counselling for prospective parents.

He said: 'It is important that there are resources and training for health professionals offering this testing and an emphasis on discussions with the pregnant woman before the test about the implications of the results'.