I had never heard of you prior to your video (where you read the amnio results) crossing my timeline. I cried. Not because of the Trisomy 18 diagnosis for your unborn 21 (?) week old baby, but because it was apparent you were not going to accept this child as he was. Let me give you some words of hard-earned wisdom, please. I've had 5 miscarriages. Those babies were 'losses'. The 4th one was a little girl whose heart stopped at 12 weeks gestation due to Down Syndrome. Later, I had 2 sons. Four years ago, at age 17, I lost my eldest son. He was born profoundly disabled both physically and intellectually. It often wasn't easy, but hear me when I say he was the happiest, most loving, beautiful child I could imagine and he made me a mother. The loving bond he and his younger brother shared was tremendous and strong. His death was a loss like no other imaginable. I would have traded places with him if I could have saved him. Back to your video. I cried because I know what it feels like when a life you love more than yourself is ripped away from you. I worry that you may make the same decision if any future pregnancies don't go as you unrealistically hope. You didn't make 'an impossible decision'. You made a decision to end the life of you son who was halfway through his gestational time. It wasn't 'a loss'. It was a calculated decision. When you try to have children, when you get pregnant, you never know what will happen. If you cannot accept the child as he or she has come to you, I would suggest you think long and hard before trying again.
PS: I don't hate you. I don't even know you. But I would suggest you and your wife take a social media break for the next few months. Really take time to reflect and heal. You put this out there for the world to see. I think it should have been private.