There is Downton Abbey season 1 suggesting it happened in England, and I supose people wouldn't let such a good alternative to avoid pregnancy pass.
If so, one could be propelled to ask how people in very sex repressive societies could get to know that anal sex was something pleasurable, possible and didn't lead to big tummies.
Could you be more specific? What episode and time stamp?
I'd like to go see for myself what you are referring to. I don't remember seeing any reference to that when I watched it originally.