mummo - had to reply as I really feel for you. Having had one child myself with a 'structural defect' that was not picked up on scan, I do know how hard things can be. My son has no pain from his condition and it's not all lift threatening, nor does it cause him any mental problems, but he has to cope with the stares, the people asking him constantly and he goes to a mainstream school. To be honest though, he is a tough little nut because of it and he doesn't let it bother him, it's me who gets upset. i had no pre-natal tests with him because was my first and I Had no other children to have to consider. I knew I would take whatever was thrown at me.
But when I was pg the next time, I asked and asked again if there was a structural deficit. If it had been the same one then I could have coped, if it had been to a worse extent, then I really don't know what I would have done, but at least I would have been prepared before the birth.
Now I am pg again and much older, I have been for detailed scans, nuchal scans etc, to see for problems., Thankfully none have been picked up, but I did this because my DS1 needs me and he wouldn't get the full attention he needs if I had another SN to deal with., This was a personal choice. Obviously I will love my child regardless when he/she is born, but I think your decision is one only you can make. You have been through the same yourself and so no one understands as much as do you.
I wish you all the best x