1 in 95 risk of downs following quad blood test. How accurate are they?

[IlanaK]

This is my third baby and I am now 35 years old. I went for what should have been the 12 week scan last week, but I was 13.5 weeks (according to date set by early scan at 6.5 weeks due to bleed). But at this scan, they put my dates forward by a week which put me past 14 weeks so they could not do the nuchal scan with the integrated blood test. Instead I was given the quadruple blood test (tests for 4 hormones). A midwife called me yesterday to say that the results put me at 1 in 95 chance of having a baby with dows which seems very high risk. I was offered amnio or cvs, which I don't want to do.

I called the private Fetal Medicine Centre toady to find out if there was any scan they could offer me, but they said the same as the NHS: too late for nuchal(I am now 15+3) and there is no further test they could do besides amnio or cvs.

So, the only think left to me is the 20 week scan, but both the NHS and the FMC said that although they look d for "soft markers", this is not diagnostic.

So now I am worried of course. I don't really want to spend the rest of this pregnancy worrying about this. So, can someone tell me if this blood test is accuarate at all? And also, can they pick up enough info at the 20 weeks scan to see if baby has down's?

Any experience of this?

no-one?

No direct experience but didn't want you to go unanswered. All the blood test does is give you a probability - and if you had been able to have a nuchal that is all you would have got from that as well. I can see what a worrying time this must be for you - but 1:95 is still good odds that your baby will not have downs syndrome. I believe many babies with DS have heart defects - there's a good chance these would show up on the 20 wk scan at least - but I'm afraid it's always going to be a case of working out the probability of xyz. If not knowing is going to trouble you all the way through perhaps you should reconsider a diagnostic test?

It is difficult to describe the accuracy of the test - when the different screening tests (blood tests, nuchal, combinations of these) are compared it is generally to see how many babies who have trisomy 21 (Down syndrome) are in the 'high risk' group rather than checking to see if each pregnant woman's risk figure is correct. The quadruple blood test will pick up just over 60% of babies with trisomy 21( if I recall correctly) - whereas the nuchal test plus bloods will pick up more like 80%...but in both cases the vast majority of people who have a 'high risk' will have a baby who does not have trisomy 21.

I've read (in journals - I am a healthcare scientist) that 50% of babies with trisomy 21 show 'markers' of this at the 20 week ultrasound - but 50% don't.

Where are you having your 20 week scan? I would try to get one at one of the fetal medicine centres rather than a general hospital (better scanning equipment eg. heart scans).

Thanks for that information. My gut feeling was that the test was not that accurate. Seeing those percentages though confirmed that. The scan will be at UCH London. They do have a fetal medicine centre, but the scan is not in that. Perhaps I can see what they say at the scan and then push to have another at the FMC.

Ilanak - I was told the odds are 1:100 just because of age/being over 35 before any testing!!

I also could not have NT and worried about the odds at the time and I must say, everybody has a right to decide what tests they take etc., and I don't know what your feelings are, but I wondered whether my experience might help?

I opted for the Amnio. It really wasn't as bad as I thought it would be, and the 4D scan was cool! They looked for the "soft markers" at the same time during the scan/testing to reassure me. My Dr said odds of Amnio causing miscarriage are (according to where I went) 0.5% i.e., 1 in 200. I figured that made it worth the risk.

Afterwards, I had a few days of obsessive knicker checking (IYKWIM) and sweated waiting for the results, but then I got an absolute definite answer which was just such a relief. No more percentages or odds.

I hope I have not offended - just wanted to pass on info from someone who has been there.

Good luck with whatever you decide .