What's God got to do with it?

I don't want kids, and don't really like kids at all. So, I find myself in annoying situations where people argue with me about having kids.
Here is the most recent one..

My co-workers were discussing different things about pregnancy, I mentioned that all those things made me glad I don't want kids. At that point, the youngest co-worker (she doesn't have kids yet), asked what I'd do if I get pregnant. I said that I won't. She replied with, "What if god* wants you to have a baby?". Unknown to her, that point is moot since I'm an atheist, but to avoid further conflict I just replied that I "Don't care" and "Do not want kids". Her next reply was, "What about people that want kids and can't have them?" I don't really understand how that applies to ME not wanting kids, but I said "I feel bad for them, but I really don't want kids." And, I made an ill-advised joke about throwing myself down some stairs if I discovered I was pregnant (I'm not very smooth sometimes). She exclaimed that what I said was AWFUL! and I went on my way.

*I find the "god" comment from her to be amusing because she doesn't seem like a fervent religious type. She's promiscuous (to put it nicely), drinks a lot, smokes pot, and goes out to strip clubs with friends. Not a particularly pious person.