Big increase in Downs risk from previous pregnancy to current one... why?!

[WhatAHooHa]

Apologies, I did post this in Pregnancy but just realised this may be a better place.

Just received the results for my Down's Syndrome screening, and it comes up as 1 in 358.
This is, apparently, low risk but I'm slightly puzzled as to why it is so massively massively different to when I had my son, 2 years ago, when it was 1 in 7637.

I was just turned 30 when I was screened with him, I am now 32 so not a great deal older. DH is 4 years older then me. I did wonder if it was higher because ds turned out to have a major heart defect, would this kind of history affect the results?

Although the letter states 1:358 as low risk, it feels extremely high compared to last time. I think I'm slightly shaken by it!

Is anybody able to help me understand what goes into deciding this figure? What factors are taken into consideration that would cause such a big change?

I'm no expert, but........

Chance of downs in one pregnancy is independant of any other pregnancy.

1:358 is low risk. That's a lot of children not born with downs for everyone that is!

They don't take history into account, only the blood tests and the nuchal fold results. And the nuchal fold isn't an exact science by any stretch of the imagination.

If your worried, you could pay privately for a harmony test.

Thanks for your reply that, our 20 week scan must be soon so hopefully we'll get some more specific info at that.

DS's heart condition is a 1 in 2000 occurrence so I think perhaps I have a bit of a pessimistic approach when it comes to odds, am convinced we will be that person once again! We are saving up for extra private heart scans because of ds' history and I'm not sure we can afford anything else.

My first was 1/7000, my second was 1/156

For me it was the nuchal fold measurement which made the difference.

Because every pregnancy is different! People can have different symptoms with subsequent pregnancies, the DNA for the child is different so it makes sense the factors driving the variables used in the NT screening could be different each time too.

I had results in the high hundreds/thousands for my first two, but I didn't have the blood test.

DC3 I had 1 in 34.. low NT, normalish bHCG and crazy low PAPP-A (the last one there was the main driver for the high risk result)

DC4 3 years later, I had a 1 in 5.. borderline high NT, sky high bHCG and normal PAPP-A (the first two were the main drivers this time)

Neither baby has Down Syndrome or any of the other trisomies.

If you are concerned though I also recommend paying out for Harmony. That will give you a 1 in 10,000 result (well, I'm 357/358% sure of it!!)

Have you mentioned your DSs heart defect to the staff? I'm sure you could push to be seen by foetal medicine on the back of that and not have to pay privately?

My DC2 had a heart defect due to chromosomal problems, so for every pregnancy thereafter (on to DC4 at the moment!), I get a fetal echo at 16 weeks and 23 weeks (or thereabouts). I'm surprised that you are not automatically being referred for one with a history of cardiac defects in the family and I would ask about a referral to fetal medicine as well.

As others have said, every pregnancy is different. My first was relatively low risk of chromosomal abnormalities, my second tests came back with a vanishingly small risk. I was 39 and the pregnancy showed a similar risk to a 15-year-old.

Maternal age is just one factor in the calculations.

And I'm sorry to sound unsympathetic, I can imagine how stressful it is! I agree that you should push for extra scans due to your family history.