Could not find a source describing your claim, only that the Second Lateran Council forbade common law marriages. Does that mean common law marriages were super common? Maybe, but Northwestern Europe was also struggling with a shortage of priests.
Although, the Fatimid Caliphate probably had Mut'ah marriages. I don't know how prevalent it was, and I doubt historians do either.
I'm not arguing ubiquity, I'm arguing against Medieval Christians thinking prostitution was "based". Men who visted brothels knew they were sinning. The Church clearly
And brothels were located in the cities. It would've been difficult/not worth the effort for most peasants to visit them.
Not every priest subscribed to Aristotelian anthropology, and even those who did still gave out penances for early-stage abortion.
I also doubt the Church kept records of the number of abortions that occurred within a single year, so whether they were common or uncommon is hard to prove.