I never know what to say!

So anyway, a friend of mine dropped into my work yesterday. I hadn't seen her in about 3 months and she stopped by to see how I was doing. Her and her husband decided before they got married 10 years ago not to have kids. He had a son from a previous marriage, and she didn't want them. Not because shes a kid hater or anything. She just doesn't think it good to bring a child into the kind of world we have today. I have been dying to ask her a question since I found out that I can't have kids. What do you say to people when they ask...do you have kids? Do you just say no and leave it at that? Do you go into your reasons, or medical history to explain? I feel the need to explain that I can't, but then I hate the way people look at you after you say that. Its a combination of pity and superiority for something that everyone should do naturally. Its not something people do on purpose, its just a fleeting look. Maybe I will go out to her house after I get off work tomorrow and talk with her, and just blurt out what I want to know.