My Dad was a GP (he retired about ten years ago). He had a couple - lovely people, very young, a bit unworldly - come to see him to discuss their failure to conceive, about thirty years ago, when I was ten or so. He was bright enough to ask what they were doing in bed.
They had BOTH somehow come to the conclusion that what was needed to make a baby was penis/belly button contact. I have no idea how anybody was getting any satisfaction, or how on earth they kept believing this after doing it once - it must have been a horrible experience. He explained (literally) the facts of life to them, and on coming home had THE TALK with me and my brother, just in case we were also stupid.
The couple in question ended up with two kids. Good old Dad.