Why did Kay leave the children in the unholy and evil environment?

I think Kay felt she had to first get free of Michael before she could do anything to help her children, and she knew that in order to do that she had to make him not want her anymore...otherwise he'd never let her go.

Now this is just my opinion... but I personally think that Kay lied when she told Michael it was an abortion, I don't see how she could have managed to have an abortion while being constantly watched by Michaels guys, nor do I see how she could have secretly found a doctor willing to do it. I think Kay miscarried because of the stress of her situation and then she saw that as her opportunity to free herself from Michael.

Plus I find it almost fitting that Kay would take her revenge on Michael with a lie, right to his face..as he lied to her face at the end of the first film. In her mind Kay was giving him a taste of his own medicine, and you could tell Kay was reveling in her brief moment of power over Michael...I always felt like she was almost daring him to hit her just to prove that she had gotten to him.

Just my interpretation of course, one of the things I love is that its never confirmed for the audience whether Kay lied about the abortion or not, so you can interpret it either way depending on your preference.