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Antenatal tests

How much does mother’s age, alone influence the combined test?

7 replies

peanutfoldover · 16/11/2019 04:30

Hiya,

I’m only 4w3d pregnant (with #2) but already worrying about the blood test. I’m 39 and I know they use your age as part of the algorithm to calculate your baby’s risk.

I remember reading when I had my first child, 5 years ago, that after the age of 35 your risk would be a certain ratio regardless of the other factors.

Is this still the case?

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Nanmumandmidwife · 16/11/2019 09:59

This info is probably helpful as it explains the algorithm www.qmul.ac.uk/wolfson/services/antenatal-screening/screening-tests/calculating-the-risk-of-downs-syndrome/
The start point is maternal age and that “guesstimate” is then revised up or down according to the NT and the hormone levels.
Many “older” women get low chance results
Also worth noting that the age related assumption is based on very outdated information and seems to be a great over estimate. Now we are seeing many more women having babies in their 40s & 50s the stats need to be revised

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Cannyhandleit · 16/11/2019 10:10

I don't know exactly how much age effects the ratio but I had my first baby at 32 and was given 1:5 chance of Down's syndrome (he does have Down's syndrome) and I am currently 37 and about to have baby number 3 with a ratio of 1:47,892. So my age doesn't seem to have made a big impact!

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peanutfoldover · 16/11/2019 19:55

@Nanmumandmidwife thank you for this. Helps to put it all in perspective. I must admit, I won’t fully relax in this pregnancy until I get that result. Not that I would terminate necessarily, but I just want to know.

@Cannyhandleit that’s really interesting, and good to hear you can get such a low odds at 37. Although I’m sure I’ve read that being over 38 tips the odds against you. Gonna check it out on algorithm

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peanutfoldover · 16/11/2019 20:04

@Nanmumandmidwife

So although it says at age 39 our risk is 1:110, it could be lower than that if the other elements of the test go well? Or is 1:110 the best it could possibly get?

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peanutfoldover · 16/11/2019 20:05

(I’m really bad at maths!)

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Nanmumandmidwife · 16/11/2019 20:31

Yes it can go lower. The calculation works on the assumption that the average is not to have one of these conditions and so the more average your results for NT and hormones are the less the chance is. This is used to modify the age related chance.

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peanutfoldover · 17/11/2019 15:59

Ah ok, that’s good to know. I was feeling a bit doomed from the start! But hope fully the other factors will be ok!