I like the irony. Most teenages pray that sex won't get them pregnant.

Extrapoliting from the original idea, what you have is effectively a form of contraception which might mean recreational sex would be the norm (no unwanted pregnancies) so you might want to build in a brake (e.g. too much of it makes the gods think you're not worthy of having children) so if you want children eventually, you need to control the amount of non-procreative sex you have).