I don't know, some people said it could happen during 2 nights in a row, and by looking at the messages around here people get abducted a lot.
Sad to say but I think I'll stay away from my game for a while until there's a real solution (bet it will be a mod and not a hotfix) and I haven't tested the EP yet. It's just that I don't like the idea of not being in control of my sims, especially for things like pregnancy. I understand some people love it or find males/females getting kidnapped and then pregnant "fun", but to me it's just disturbing and I really hate the aliens coming with this EP.