Misconceptions over 'Increased risk of Down's Syndrome'

[Lorechka]

Hi there

I am 13 weeks pregnant and I have just had my first scan. Despite everything being 'perfect' with the ultrasound, I have been told today that I have a 1:114 chance of having a child with Down's Syndrome. This is supposedly within the increased risk category.

Whilst this was initially scary, I have now done a bit of 'homework' and discovered how misleading these statistics can be. When we are given a result of 1:114, or whatever it happens to be, this does not take into account the accuracy of the screening in the first place. Screening for Down's Syndrome is reported to be around 87% accurate which means that there is a 13% chance of the results being wrong in the first place. This percentage increases or decreases depending on whether you are in an 'at risk' section of the population. if you are less than 30 years old, then there is an even higher chance that you will have a 'false positive' reading. Added to the individual risk (in my case less than 1%), there is actually a much lower chance than we first think when we are told our results. See the following article for a more scientific analysis:

www.downsyndromeprenataltesting.com/how-accurate-is-the-new-blood-test-for-down-syndrome/

From what I have read, this has reassured me greatly and I hope that it can do the same for other people and to reduce the unnecessary amount of stress this can cause.

That is not to say that having a child with Down's Syndrome is a bad thing and even if the result was 100% accurate, I would not consider termination.

BW
Lorechka

i hate the whole downs syndrome and abnormality testing.. I am disabled and it disturbs me that they consider it normal to screen for these things...

I completely understand why they screen. I wouldn't terminate for anything not life threatening but I would want advance notice of anything else so I could prepare myself for any challenges we may face.

That article relates to a different test available in the US and not the combined screening test you would have had if you are in the UK and on the NHS.

It is an article is pseudo science propaganda written by a man with a Down syndrome child who is opposed to screening- he is neither a scientist or a doctor and is pursuing a personal agenda. There are a lot of wackos on the internet spouting all sorts of crap. If you want to talk to someone non- nhs about the result why not try the ARC for a more balanced and factually correct view?

Can I ask what might be an ignorant question?

Even if Downs Syndrome wasn't screened for at 12 weeks would it be detected at the 20week scan anyway? I.e would things be seen, structure of organs or something, that would indicate the condition was present?

I do see why they screen. I would want to know or at least know it was a possibility even though I wouldn't terminate. so I could prepare myself mentally. something like downs is quite visible even at birth and to suddenly see my baby and find out it had something that would affect its life so much would be very upsetting. There are people who would want to terminate and we cannot judge them as the child could suffer a lot, so they may be thinking of preventing their child's suffering, and it's not just downs it screens for, the baby could have something much more serious.
Some people might want to plan an adoption as they may be unable to care for the child, they may have disabilities themselves or already have children with disabilities or be a teen mum.

There's been a lot of research into improving the accuracy of those likelihoods so they are as accurate as possible with narrow error bars. That's why you have to have your blood test in a specific week etc.

I understand its stressful but whilst 1:114 is higher than background likelihood its still less than 1%

I accepted all tests despite only thinking termination was an option if a condition was incompatible with life because if ds had had a disability I wanted to know and get paediatricians at his birth and mentally prepare myself to deal with surgery etc.

As fred says, that article is talking about the new non invasive tests- Harmony, NIFTY etc. NOT the test done on the NHS in the UK.

What it says is true for all diagnostic tests. You have to take into account the underlying prevalence amongst your peers to fully understand the significance of a positive or negative result. Eg an HIV test may have a very very low false positive rate, but if you are someone who has never had sex, injected drugs nor had a blood transfusion, and you get a positive, then it is far far more likely that it is a false positive than a true positive, no matter how accurate the test is.