Down's combined test: NT and bloods don't agree

[britgirl82]

Our 12 week scan was this week.

On the ultrasound everything looked great. Baby was measuring a few days big, strong heartbeat, and a normal nuchal measurement. Sonographer didn't check for a nasal bone (something I regret not pushing for now) although she didn't make any comment about it not being there if that makes sense.

I got a call today though and my Down's risk with bloods is 1:90. I realise this is still basically a 99% chance that the baby doesn't have Down's, but I'm confused as to how my bloods and the scan can so obviously disagree: the scan wouldn't have increased my risks, and I'm only 30 so that wouldn't be high-risk either (think the baseline for age 30 is 1:940).

So I'm thinking that the bloods must have been very off to get that result (I don't have the actual figures). I've spoken with someone at the ARC who was awesome and said that it's more than likely natural hormonal variation rather than an indicator of a problem since the scan was good.

Throwing a spanner in the works is the fact that I had chemotherapy last autumn. I've been told definitively that this won't have increased the chances of an abnormality, but I'm wondering whether it could affect hormone markers in my blood: I had my AMH levels tested in March and they were horrendous (basically menopausal), but clearly wrong, since I feel pregnant first month of trying

Anyway - does anyone have any more knowledge about how bloods and NT measurements can 'disagree' or whether chemo could still be messing things up?

We're not going to have an amnio, since we wouldn't terminate, but I'd like to be realistic about the chances of a disabled child so we can prepare ourselves.

Thanks.

 

[chattyB]

The NT scan measures the fluid behind the neck and the bloods measure Papp-a and free B-HCG.

The bloods are measured in MoM (multiples of medium) and both should be 1.0. Any variation from this can throw your risk ratio "out". With DS, the HCG is usually higher (as in 3 or more times the MoM) and the Papp-a is much lower (around 0.4 or lower I've been told). The scan, blood tests, age, weight and whether you smoke are all taken into account when calculating your ratio.

I had a 1:11 chance of my baby having DS with a NT measurement of 3.5, Papp-a of 0.67 and BHCG of 0.93. It was my age (35), lower papp-a and NT measurement that drove my risk higher. We chose to have the amnio and very pleased to say that baby is fine.

Interestingly, my baby also measured larger than expected at the scan and I also has chemo for cancer, 6 years ago.

 

[britgirl82]

Great to find another chemo-veteran Glad to hear that all was well after the amnio.

I'm trying to get hold of the hospital again to get my actual measurements, but guess I'm just looking for reassurance. When we had the AMH scare, my ultrasound was perfect and I was having regular ovulatory cycles, so we just knew the blood results were wrong. It was still really stressful though until I made a conscious decision to ignore the blood results and trust what I could see with my own eyes.

Feels like it's the same thing all over again. I realise the baby could have Down's and that scans sometimes don't pick it up, even at 20 weeks, but I'm having a hard time believing the bloods when everything else looked fine. I've been googling like crazy and can't find any answers: everything seems to be advice for when the nuchal is bigger than average.

Wish I'd never agreed to the bloods now. It's just raised more questions.

 

[Inka]

Hi,

Sorry to read your post and I can't provide any advice from experience just that my NT measurement was within the normal range 2.2 and so the hospital said I didn't need the bloods as the measurement ok but I could if I wanted. I had the bloods as OH wanted to and in my last pregnancy baby measured 1.7 so thought I may as well. With my first baby I didn't have bloods as I again had the option and was happy with the measurement.

If I was you now I would want all the information, measurements and hormone levels so you can know exactly what has been considered. I hate the way the nhs leaves you in limbo with limited info (you may not have gone nhs but having done both I was shocked at the difference in information sharing).

As you said the score still very low in terms of likelihood but I realise this is stress you don't need, hope you get some info and good advice here.

Inka xx

 

[britgirl82]

Thanks.

Yeah NHS. Although we're moving to the USA next week so will then be going private and am expecting much better care.

If it's Down's that's fine - it's not the end of the world and there are worse things a baby could have - but I would like to be as clear about the risk of this as possible. This has just raised more questions!

Interesting that your hospital did the measurement first and then bloods based on that. The ARC seemed to agree: she said that they don't really agree with using blood tests at all due to their unreliability for various reasons (apologies if I'm misquoting - please don't take this as gospel about them!). Crazy how different hospitals have different attitudes...

 

[SarahSausage]

Can you get the new MaterniT21 blood test in your area?

 

[AmesLouise]

I just went through all of this a few weeks ago. I did all that NT testing, ultrasound was very normal and my blood results were 1:82 for downs baby. I did decide to have the amnio b/c I didn't think I could enjoy this pregnancy with this big unknown. Our genetic counselor showed us results of people that also came back with "high risk" numbers and what there numbers were when they did find out their baby definately had downs. Those numbers were around 1:10. So, 10 days later I got my results and it was all a false positive! So frustrating to have to go through all of this for nothing! I am 39, so I knew that I was at higher risk than those younger! I really wish you all the best- I do believe ultrasounds these days really do tell alot more than all those crazy blood tests!

 

[everthingX]

Hi Hun,

Sorry to hear you are going thru this as well. Its a shock when you get that call isn't it. Put the fear of god in me.

I have also had high risk come back, 1/110. My scan was perfect 1.2 but my bloods HOG was 2.0 and papp was 0.38 my age is 37. I am not having Amnio too scared I lost my first pregnancy so know how fragile it can be and don't think I'm strong enough to terminate, I just couldn't do it. Some of my inlaws don't agree with me but its my baby and I'm here to do the best I can.

I have been going over my results until I go round in circles. They don't add up to me either if scans so perfect but they say a child with mild downs can have good scans it does mean by a good scan it rules out the other problems so they are only focusing on DS.

We have our 20wk scan next Thur and part of me is terrified. I am seeing someone higher up as not having Amnio. I have said to my partner if they were to find markers maybe I will have Amino so we know and can prepare, but don't think I can like you I cannot terminate.

I can only hope and pray the scan goes well its such a horrible wait but as more time goes on you seem to settle down a bit. If you ever need a chat as both in same situ feel free to PM me.

I am in UK and asked about the new 21 blood test, its still only on trials here but is available in some places in US so if yr moving there maybe good news you could take that test? Harmless to baby.

Good luck hun, in time things will seem more clear but keep yr mind positive for MOST high risk ladies they have healthy babies. xxxx

 

[pj67]

Hi. With my 2 nd pregnancy I had a normal nuchal scan. I think the measurement was 1 so it was very normal. With the blood test my result came back 1 in 26 risk of downs syndrome. I did have an amniocentesis and the result was normal.
I also had a high risk result with my first son, 1 in 86 but this was before nuchal scans were done so was with the triple blood test. I think there must just be something with my blood that would always give a high result.
I'm sure I read that if a nasal bone is present the risk halves so if you got another scan that would be very reassuring. I'm sure they would have said if they didn't see a nasal bone though.
Good luck, I'm sure everything will be fine.

 

[maxalias]

I had a nuchal reading of 10.6mm! extremely high and then my bloods were all quite normal and that leveled out the ratio to 1;15 for downs. I was 1;1200 for edwards syndrome, I was that 1 and baby died just before 18 weeks. Next pregnancy I dont want to know the numbers, It is so scary. I have to have an amnio now anyway because of having history so I will wait to see what that says. It is so scary and until you know for sure the stress is not good at all, I wish you a happy and healthy pregnancy