I made my dad laugh out loud when he was recovering in the hospital after his brain aneurysm. He was laughing, and I was mortifed. I had just admired what I thought was a baby bump on a lady, and asked the woman how far along she was in her pregnancy...and horrifyingly...she wasn't pregnant! It had happened at the entrance to the hospital, and I was probably still red in the face from blushing, when I got to my father's room. I remember telling my father what had just happened, and he laughed out loud.
Honestly...I have never commented on any stranger's protuding belly ever again. No matter how obvious it is that they are pregnant. Cuz, you just never know.