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Online trisomy calculator

(16 Posts)
partridge Wed 23-Feb-11 18:57:02

Has anyone tried this?

Does anyone know how accurate it is? If I input the nt MoM that they calculated it comes up with a risk factor similar (minus 46) to the one that I got from the NHS combined test. If I use the nt and crl measurements my risk decreases by about 2,000. I have used the same beta bcc and Papp-a values.

To be honest I think they have miscalculated the nt MoM judging by the nt to crl measurement (I compared it to an nt MoM chart - mine came out at 1, theirs at 1.38).

I would love to hear others opinions. I am not overly worried but the second result is far more reassuring!

partridge Wed 23-Feb-11 18:58:12

Sorry - beta Hcg obviously! I am sorry I've been so technical...

Sparklies Wed 23-Feb-11 21:31:23

Whenever I've used it, it's always given me much "nicer" ratios. Same applies to other people I know as well. So I don't put a lot of faith in it.

However, it is useful for putting in different values and seeing how they relate to each other e.g. fiddling with the age, CRL etc.

partridge Wed 23-Feb-11 22:42:12

Thank you for this. Do you mind me asking the discrepancy? Because with the Nt MoM as they had calculated the results were almost exactly the same, which gave me some faith in it. It was when I changed this value to what I think it should be that the results were dramatically altered.

Sparklies Wed 23-Feb-11 23:52:37

I think it was the bloodwork that was off. The MoMs tied up with the NT measurements/CRL but that's probably based on a more standardised table. As soon as the bloodwork came into play, the risk ratio was quite drastically different. e.g. I'd been told 1 in 34 by the Fetal Medicine Centre run by the man who invented the NT scan.. but the calculator quoted me 1 in 140. I know who is probably right but the calculator odds did look much nicer!!

partridge Thu 24-Feb-11 06:30:48

Thank you. Best of luck. These odds in real terms seem actually really good, but become so skewed when we are talking about babies and are used to odds in the thousands.

Sparklies Thu 24-Feb-11 12:59:03

Thank you! And yep, exactly! In the real world, we'd buy a lottery ticket based on a 97% chance of success, but when we see everyone else with their 1 in 4000s, it doesn't feel so great..

Regardless of actual "score" - apparently only 5% of women who screen positive have a problem at all, so 95% of women are worrying needlessly it turns out!

partridge Thu 24-Feb-11 14:27:30

Absolutely and I am sure your baby will be absolutely fine. I called the wolfson centre and they were brilliant and actually re-calculated the nt mom based on the crl and nt measurement.

Turns out the original lab has miscalculated it. My nt was 1.9, but to get the 1.38 mom they came up with it would have had to have been 2.6.

It actually makes me really angry as my risk has now gone down to 1:2647 from 1:700. Never bad in the first place, but a huge difference really and even more reassuring.

partridge Thu 24-Feb-11 14:29:07

Ps the online calculator turned out to be really accurate in my case. So don't discount your better risk - I think some labs use different software but that one worked for me.

Sparklies Thu 24-Feb-11 15:50:51

That's awful they got your NT MoM wrong :-( I'm glad you had it fixed! I know my NT MoM was right unfortunately, and I do trust the Fetal Medicine Centre in London with their stats more than most places. A lot of it depends on gestational age too, so if baby is measuring behind or ahead (and they correct for this, or don't correct for this) it can skew the results. There are lots of different ways of calculating it before you even reach the formula they might use, which is why we all have such different numbers!

But I am glad you've had reassurance - hurray!

dinky1975 Fri 17-Jun-11 21:21:50

I am 35 and 12 weeks pregnant with my second baby (ds 21months). I went to the Fetal Medical centre for my NT yesterday and the results were:

Great scan: CRL55.4, NT 1.5 and everything else fine
Blood (not good) hcg 3.0436 (MOM) and PAPP-A .5275 (MOM)

combined score was 1:2278

Since then I have been researching low PAPP-A and have come across many other posts from people in similar positions (good scan, bad blood and 'old') and their combined results were much higher (ie at greater risk), then I found this post and went to the calculator and my results and got 1:319.

Does this sound normal? Is it really possible to get such a good score with such blood results at 35. Can anyone help?

I guess I will call FMC and ask them to confirm (I also want to ask what the abnormal blood work could mean in addition to chromosomal abnormalities) but if anyone can help that would be great.


partridge Sat 18-Jun-11 13:55:30

Hi there. From my understanding the fmc take lots of other factors into account which can skew the odds, for example nasal bone. So in effect I think their testing is more comprehensive and accurate than nhs testing (or the calculator). I would be v happy with those odds and try not to think about them any more.

I have had my faith shaken in these screening tests due to what seem like some pretty arbitrary results from friends with worse stats etc.

lalitN Wed 18-Jan-17 18:30:38

My wife gone through dual marker after 12 weeks and here are the results.
PAPP-A - .56 MOM
HCG - 2.45 MOM
CRL - 55.3 mm
NT - 1.20 mm
NT MoM - .82 MoM
The Biochemical risk for Trisonomy 21 is 1:90 and negative screen, I am doubtful on that.please help.

zambean Thu 19-Jan-17 09:58:59

Hi lalitN,

You might have been better to start a new thread with this, but...

Those numbers don't look too terrible. I had similar PAPP-A and bHCG results, but a "worst" NT, which meant my risk came back as 1:23. We had NIPT and it came back all clear.

How old is your wife? That makes a big difference too to the risk factor you receive. I am 35, which is why mine was 1:23. Had I been 20, I think the same other bloods and NT would have made me technically low risk. And of course, it is just a probability. At this moment, either your baby has Trisomy 21 or it does not. It's not actually the case that is a 1:90 chance now that your baby will born with Trisomy 21. What it actually means is that of 90 couples with your results, one would get a positive result.

Have you looked into NIPT? I really recommend it. Should cost no more than £500 and you will get the results back in a week.

lalitN Sat 21-Jan-17 14:56:33

Hi zambean,
Thanks for your response.
She is 32 years old.Her combined risk (with NT) is 1:570 while triosomy 21 is 1:90.
We have met with genetics doctor and he preferred amnio for us.
We have our 6 year old daughter that has problem,we have not gone through these tests in her previous pregnancy.I don't know the exact problem,she has low understanding and unable to speak proper letters.
We all three has normal Karotyping.Doctor has choosen chromosome microarray for her now.
Anyway as you suggest, doctor first choose NIPT for my wife but when he saw my daughter, he said to go for amnio for us.
We both are very scared, need a health baby now.
Please suggest, are we going in right path.

PrenatalScreeningcloud Sat 15-Apr-17 21:22:35

Message deleted by MNHQ. Here's a link to our Talk Guidelines.

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