Medieval priests used penitentials to define rules and punishment. A lot of prohibitions involved sex and some were odd. (To be fair, in an age before cars, guns, and corporations there wasn't much other behavior to regulate.) In a few regions, the penalty for performing fellatio on one's husband was greater than the penalty for killing him.
The penitentials offered a labyrinth of penalties and prohibitions. Among other things, it left only about 4 days a month during which it was "legal" to have sex. Even those limits weren't enough: married couples could be prosecuted if they were known to enjoy sex too much. Pope Gregory (~540 to 604) declared that marital sex was blameless only when there was no pleasure involved.
Perhaps unsurprisingly, during the period of the Dark Ages when these penitentials had the most influence - from about 500 to 1050 - Europe's population actually shrank.
So that's kind of interesting.