My experience was similar, V.high NT the initial combined results came back high risk of Downs.
I had a CVS. Clear of Downs, Edwards & Pattau syndromes. Showed I was having a boy.
NT stayed large, nothing else came up as an issue other than a couple of very small holes in the heart and polyhyraminos (extra amniotic fluid).
Waters broke early at 24+ weeks, delivered at 25+ weeks.
After 3 cardiac arrests my son died after 39 hours of life in my arms. I don't regret meeting him. Still can't say if I would've made the same decision if I'd known the outcome.
6 months later his blood tests came back showing a syndrome that isn't tested for in a CVS/Amnio (also deadly) and had to wait a further 6months to see a geneticist to find out if it was 'safe' for me and DH to try again.
Fast forward 2 years, I'm 22 weeks, everything looks great on scans so far and I'm both happy and terrified.
I hope yours is a happier story OP 
Sorry to all of you who have been through similar, it's the most unique kind of pain, even now 