David Lerman wrote:

At 06:32 PM 8/11/97 -0600, you wrote:

Hey, I can't figure out why Nodoka went for Genma either, and Urd
doesn't strike me as remarkably brighter than Mother Number 1.
And remember, it only takes once.  Maybe she was drunk...

  Maybe Genma-Nodoka was an arranged match.

  Urd is not dumb, only lazy.  It is possible that during one of her party
times she did something she shouldn't have.  Except for the two facts that
Genma's stomach is far more important to him than his libido and that
Nodoka has a very sharp sword, I don't think that Genma would much
objection to cheating on her.

I would estimate that Ranma was probably conceived almost immediately
after the wedding.  Nodoka's pretty young looking after all.  If you 
pushed his date of conception back a few 
days...  Imagine if you will as batchelor party being held in a bar.
And an Urd who just been demoted to Goddess 1st class after stepping
over the line once too often, and who has descended to Midgard to
drink away her sorrows...

Now there's a lemon for ya.  But I can't write 'em.  

Five years later, Urd decides to dump Ranma on Genma for a little
mortal experience, and Genma wisely decides to take his act on the
road before Nodoka has a chance to consider her options.  

Of course another approach would be just to have Urd magic the kid
out of herself and into Nodoka before birth, which would certainly
save Urd a lot of inconvenience.