Risk cut-off for amniocentesis

[flibbity]

Just had my booking appointment and had blood taken for the combined test: my first scan is later in the week. At my booking appointment, the midwife said that I'd only be offered an amniocentesis if my risk is higher than 1:150.

Everyone has a different idea about what risk they're happy with, and it's something I'd thought about earlier in my pregnancy and decided that I would want diagnostic testing at a much lower risk than that, probably up to about 1:500.

If I'm not comfortable with my screening risk -but it's lower than the national guideline - can I request diagnostic testing? Or would I have to get it done privately, and is that even possible?

I'm in my late 30s, if that makes a difference. I thought I read somewhere that diagnostic testing was offered to everyone over 35, but in my hospital your age is just fed into the computer program along with the screening results.

I know I'm worrying ahead of time, probably about something that won't happen, but I'd like to know the options before my scan so that I can discuss it with them.

This is something I'd thought about too. I would have wanted an answer up to about 1:500 just like you, because as you say everyone's tolerance to risk is different.

As it happened, my screening results were very clear cut with obvious courses of action. With DS1 it was 1:8000. With DS2 it was 1:15 and I had a CVS.

I wonder if the Fetal Medicine Centre in London would do a private CVS or amnio? Alternatively, Antenatal Results and Choices might know?

I suspect that if your risk is lower than their cut-off, unless you have previous history of a fetus with chromosomal abnormality, you wouldn't be offered CVS automatically.
The FMC that mummy mentioned is a private clinic and would do CVS/amnio if you wanted. I had a CVS there.
Best of luck -- hope your risk comes out as low so you don't have to make any difficult decisions.

Thanks, both. The Fetal Medicine Centre looks really good - I think we'll book a scan there if our results aren't clear cut.

Thanks for the best wishes, Yaya

I had a "second opinion" scan at the FMC after our NHS risk result was 1:104. The FMC risk rating was 1:175 but they also gave me a risk rating for Edwards and Patau syndromes (which the NHS generally doesn't do) of 1:42. I had a CVS and all was clear.

The FMC does CVS/amnios as well as scans - I believe they recommend a CVS/amnio if your risk rating is over 1:300, so a bit lower than the NHS's cut off point. However, I believe they will do it whatever your risk rating, since it's you paying.

Interestingly the NHS cut off used to be 1:250, it's only in recent years it's gone to 1:150. In theory that is because testing has got more accurate but I wouldn't be surprised if cost comes into it a bit...

I am sure you know this but the risk of miscarriage from a CVS or amnio is about 1% (though lower if done by a very experienced consultant such as the FMC professor or the consultants at large London hospitals). By contrast 1:500 is a 0.2% risk. But obviously that risk may outweigh the miscarriage risk in your eyes.

Hopefully all will be well at your scan and you won't get a high risk result.

With my first pregnancy our Down's risk was very low, less than 1 in 40,000 I think, and the doctor said he wouldn't advise an amnio or CVS and asked if we were happy with that - I got the impression the choice was still ours, but also that they would really try to talk us out of it if we said we wanted it. (This was the NHS - Kings in London)

Also - I'm a maths geek so this is how I think about it - if you're told that your risk is 1:500, and the CVS miscarriage rate is around 1.5% I think, then the risk of miscarrying a non-Down's pregancy from having the CVS is 1.497%, compared to the chance of actually having a Downs pregancy of 0.2%. I.e. it's nearly 7.5 times more likely that you miscarry a healthy pregnancy than that your baby has Downs.

Also worth thinking about what you would do if you got a positive result - if you wouldn't consider terminating anyway then you might not want the risk of miscarriage - anyway, I'm sure your midwife / doctors would go through all this with you and at the end of the day it's your personal choice as others have said.

Good luck.