Why not just make it that Ranma gets stuck in girl form, if she gets
pregnant?  Depending on the circumstances under which the pregnancy is
initiated, that could have some very interesting connotations.

	A possibility would involve Akane. I know people dilike screwing around with 
the Akane who is actually almost normal in the Ranma world. But what would happen if 
Akane assidently was hit by the Water of the Drowned-man and permanently became a man. 
Would Ranma take a female form to be with Akane? This could lead  to an interesting 
post-series based on the development of onna-Ranma, and could involve Ranma pregnant by 
Akane. Bizarre twist, huh?

Though it's the only semi *normal* way I can see Ranma getting pregnant...
Love potions and passion spice are a little over-used ...

Kun-chan...