hi gingersarah, sorry to hear you're feeling worried.
To reassure you - those are very good odds, particularly considering your age. (Not being rude, just that the odds for the average 35 year old, for example, before testing are around 1 in 350). This means your nuchal fold and your bloods were both very good.
Also, the blood results on their own can only decrease the risk by a factor of 20 - so if you just had the blood tests at age 35, then the BEST result you could get would be 1 in 6000 ish. This means your nuchal fold measurement was also good, as it's reduced it down further to 1 in 8600.
Does that make sense?
As for amnio - only you can make that choice, but given that amnio carries a 1% risk of miscarriage, there is a far greater risk of losing a healthy baby from an amnio than you have of your baby having Down's.
If it helps, our risk factor is 1:6500 and this is considered very good, so yours are even better than ours!
Personally, I would have an amnio with those odds, but it's not my decision to make. But it's worth remembering that an amnio will tell you for certain about chromosomal abnormalities, but there's still no guarantee that everything is ok with the baby. Maybe if you ruled out Down's you wouldn't be worry free, you'd just worry about other things instead, iyswim?
Sorry, hope I'm helping rather than making things worse!
LMD x