Crunchy effects of pregnancy?

[Eloi]

Depends on the DM. I have a tendency to run campaigns where you might not be getting the option to go rest for a few months. E.g. the "you've been kidnapped by a demon who demands you get something for him" type.

If you're characters don't have enough time to rest for the duration of a pregnancy, they don't have enough time to cause a pregnancy, in my opinion.