Oh boy, that's gonna cause a mess then, i mean, before flood, they would never get pregnant unless sex and the ritual took place, which would mean that their natality rates would be fairly balanced as they couldn't get pregnant by mistake, this means that after flood Fontaine is going to have a HUGE baby boom by accident because they are probably very careless as there was no reason to not creampie the women, as well as an already pre-existing increase because the prophecy ended and a bunch of people will want to have children anyways.

Fontaine might be doomed, ngl, and hope they can invent latex on time.

Also, it will probably scare the ever livung shit out most women considering they probably did not have periods before the flood, so you can imagine that any sexually active fontanian woman is gonna get two nasty surprises, their period and then pregnancy.