When my little sister and I were really young (maybe ages 6 and 4) our mom was changing the sheets on our parents' bed for laundry day and we saw a dark stain on the mattress. When we asked what it was, mom tried to skirt around explaining periods by saying, "well sometimes when you're asleep you can't control when you have a bad surprise." For probably ten years(!) we thought Mom had had diarrhea in her sleep... yes, even after we learned what periods were, we didn't make the connection!
A childhood belief about periods

others believed things like this
- I also used to think that Mommies didn't have periods. I thought it went away once you had a baby.— T
- i used to believe when iwas young that during periods, one bleeds through thier breastsAnon
- i thought the phrase "getting a boner" referred to men getting their periods. — astrid
- When my mom was a child, she thought that while girls had periods, boys had hemorrhoids!Anon
- I used to think that guys had periods, too. — Laurie
- i used to believe that women wore bras because their periods happened in their boobies.Anon