Scientists Back Down's Test

5 March 2014, 11:34 | Updated: 5 March 2014, 11:48

Great Ormond Street Hospital

Leading scientists say a new, more accurate Down's Syndome test being trialled at London's Great Ormond Street Hospital should be made available across the NHS.

Non-invasive prenatal testing (NIPT) - which is 99% accurate - can predict whether a baby has Down's and also screens for the rare genetic conditions Edward's syndrome and Patau syndrome.

NIPT is currently only available in private hospitals but is being considered for use on the NHS by the UK National Screening Committee.

It will make a formal recommendation on whether to introduce the test once the results of the trial at Great Ormond Street become known.

In a new development, a scientific impact paper published by the Royal College of Obstetricians and Gynaecologists (RCOG) supports giving the test to all women who want it in early pregnancy.

At present, testing for Down's involves a combination of an ultrasound scan of the baby and a blood test for the mother.

Experts then estimate a woman's chance of having a baby with Down's. Those found to be at high risk can opt for invasive tests - amniocentesis or chorionic villus sampling.

Both carry a one in 100 risk of miscarriage.

The new NIPT blood test detects a baby's genetic material and does not carry any risk of miscarriage like the invasive tests.

Professor Peter Soothill, consultant in foetal medicine at the University Hospitals Bristol NHS Foundation Trust and author of the scientific impact paper, said: "This is the most exciting development in pregnancy care in many years.

"The new test is so accurate that the number of women who will need invasive tests is going to fall very dramatically while still informing those who wish to know about chromosomal abnormalities.

"The test is not yet available on the NHS but we think it will become a primary screening tool for all women who wish to know about foetal chromosomal abnormalities."

Advantages of the test include its high accuracy rate (over 99%) and ability to avoid invasive tests.

However the experts said one disadvantage is that pregnant women may occasionally be informed of findings of uncertain significance, such as when there is a discrepancy between the chromosomal make-up of the cells in the placenta and the cells in the baby.

Dr Sadaf Ghaem-Maghami, chair of the RCOG's scientific advisory committee, said: "The potential for this technology is exciting and will provide much more accurate results for pregnant women.

"However, 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."

About 750 babies with Down's syndrome are born in the UK each year.

Dr Anne Mackie, director of programmes for the UK National Screening Committee, part of Public Health England, said: "The UK National Screening Committee (UK NSC) is currently working with clinicians to trial the use of NIPT in the NHS and will make a formal recommendation on whether to introduce the test when the results of the trial are known.

"The UK NSC welcomes research undertaken by the scientific advisory committee at RCOG to see whether the test would be effective in the identification of chromosomal abnormalities in unborn babies.

"Early indications suggest that using NIPT to screen women who are found to be at a higher risk of having a baby with Down's syndrome would enable earlier and safer detection of the condition."

She said all women were currently offered testing for abnormalities as part of the existing NHS programme.

Elizabeth Duff, from the National Childbirth Trust (NCT), said: "The potential for new and, above all, non-invasive approaches to screening is an encouraging step forward. It is vital, however, that these tests remain an option for parents-to-be, and that they are kept well informed of their right to refuse if they wish.

"Whatever the result, it should never be assumed by health professionals that expectant parents will decide on a particular course of action - the decision is theirs and should be respected and supported.

"Personalised support and an ongoing relationship with a skilled midwife are particularly important for women in this situation."