NHS to offer safer test for Down’s syndrome

This week the UK NHS has announced that from 2018 it will pay for about 10,000 high risk women to have non invasive prenatal testing (NIPT). This will reduce the need for invasive procedures such as amniocentesis and prevent hundreds of miscarriages.

The chance of having a Down’s syndrome baby increases with age.  Under 20 years, the risk is 1 in 1500.  At 45 the risk is 1 in 50.

Down’s syndrome is caused by an extra copy of chromosome 21 which can lead to a wide range of symptoms.  About 775 children are born with Down’s syndrome in the UK each year.

In most counties a pregnant woman is offered prenatal screening using an ultrasound scan and a blood test between weeks 11-14 of pregnancy to determine if the baby has Down’s syndrome.  This screening method is not 100% accurate and has a relatively high number of false positives.  In the UK, if prenatal screening shows a risk of more than 1 in 150 the couple are offered an invasive procedure, normally an amniocentesis, to determine for sure if the baby has Down’s syndrome.  This equates to about 10,000 women annually. But since amniocentesis carries a 1 in 200 risk of miscarriage, about 2000 of these women decide they do not want to go through an amniocentesis, either because they are worried about miscarriage or they would not wish to abort a Down’s syndrome child.

NIPT measures DNA fragments in the mothers blood at around 10 weeks of pregnancy. As it is 98% accurate with significantly less false positive results, it is estimated that as many as 3000-5000 amniocentesis procedures will not be needed, which will greatly reduce the number of miscarriages resulting from this procedure.

NIPT can detect other syndromes besides Down’s.  Patau’s is an extra 13, Edward’s is an extra 18 and Turner’s syndrome is a missing X chromosome.

Dr Anne Mackie director of the UK National Screening Programme told the BBC News website “I think it has the potential to make a great deal of difference. It will give more accurate results and decrease the anxiety in a significant number of people.”

My colleague Professor Lyn Chitty has been the driving force in developing NIPT in the UK. She told the BBC “I’m really pleased that they’ve made the decision to introduce it into maternity care for all women, we know many are going to the private sector for it at the moment.”   Lyn appreciates that testing may increase the number of abortions but she has done research into this and found that some women are using it to prepare for the birth of a baby with Down’s syndrome

Recently we reported on a documentary by Sally Phillips who presented her views on living with children with Down’s syndrome.

It may be possible in the near future that using NIPT we can test for more complicated genetic diseases.

Image credit – http://nipt.co/NIPT.html