I might reply "I appreciate that you're trying to cheer me up, but it's still pretty awful not being able to have my newborn home with us."
I like this. It acknowledges that they're trying to be nice, while still pointing out that they're actually being somewhat thoughtless. There's a difference between "being nice" and true empathy.
When I was born (oh-so-many years ago
), I was very premature and had to stay in the hospital for two months. My parents lost another baby, my twin, at the time. I was OK (miraculously, really), but I still had to stay until I made weight.
My folks lived in a rural town. The hospital was a half-hour away. They only had one car, and dad needed it for work.
This was really rough on them, especially Mom. She went as often as she could, but it wasn't always possible. (Dad would make side trips to visit me, even though it meant he had about a five-minute lunch "hour.") But people would say, "Oh, at least this one is OK!" "Oh, at least you know she'll be coming home!"
To this day, she says she's not sure how she managed to not let them have it. (Personally, I think she should have.)
I understand a little what she went through now. My elder was in the NICU for a week after being born. (He wasn't in any danger, but they wanted to be sure they had some of his heart issues regulated.) But I lived a five-minute drive away and could camp out in the NICU all day with him if I wanted. That wasn't possible then.