If I recall correctly, it was said in Predator 2 that he didn't kill her because she was pregnant. I haven't seen it in a long time, though, so I could be wrong.
That is true. That is why he did not kill her. Back to the topic, I saw th movie and I quite like it. I was never scared by any of the the other Alien movies so I didn't care about the suspense factor. I just wanted to see teh Aliens fight the Predators and I got that.