Hi there An,
I feel very strongly that if you would not terminate the baby no matter what then invasive testing is unnecessary. I just lost a baby last year to Trisomy 18 Edward's Syndrome and we found out at 19 weeks during an ultrasound. We did not have the amnio, no need at that point, we already knew he wasn't going to make it and we knew in our hearts that it was Trisomy 18. Turned out it WAS full Trisomy 18, a fluke.. I carried him all the way until I went into labor at 37 weeks, we did a c-section and I got to see him alive for a short time before he passed in my arms... just the way I wanted it. He actually survived and hour and forty -five minutes.. which I got the last 10 after a botched c-section

(
I am now 39 and pregnant again.. very scared, BUT I will still have no invasive testing done, only the NT Scan and an ultrasound. They can see everything they need to see there, we saw it all with Jonathan (the son we lost). It was very clear.
This is my 6th child including Jonathan, and we have all healthy babies, so I just have to trust in the Lord and He will do the work. I am only 7 weeks and 2 days, so I am still in the waiting stages and it IS difficult, don't get me wrong, but the day will come soon when I will know if this baby is healthy or not.
I hope this helps you in your journey. You can look at it two ways.... if you absolutely HAVE to know if there is anything wrong with your baby, have the testing done. If you would keep the baby no matter what, then the invasive testing to me is not worth the risk of losing your baby, there is a risk of miscarriage... and that is hard to live with. Plus, ultrasound can tell you what you need to know. It won't diagnose.. but it can still tell you a LOT.
Good luck, my prayers are with you!! ~Christina