My stomach involuntarily turns whenever I see an obviously pregnant woman.
When I was 4 or 5, I had a favorite neighbor lady who had one of those "fancy" refrigerators that dispensed drinks on the outside of the door. She always kept it filled with kool-aide for me. So another summer came along and when I rang her bell to ask for a drink she answered the door very pregnant. It disgusted me so much to see her all deformed and misshappened that I ran away, and pregnant women still bother me to this day.
I know it's a strange aversion, it was just too traumatic an experience for me I guess.