Oh wow, a long thread already and I haven't read the responses, but this is a topic near and dear to my heart.
I am a stepmom, but never had any children of my own. I have absolutely zero regrets. I always assumed that having children was something I'd maybe get around to someday, IF I found the right partner. Well, by the time I found the right partner, he was twice divorced with two young boys and had had a vasectomy, so I had to make sure early on that I was comfortable with the idea that if this man was "the one," I was OK with the idea of not having children with him. As the years went on, we occasionally discussed the matter (usually him asking me "Are you SURE you don't mind not having kids? Because if you do, we'll make it happen..."). Each time I remained quite content with the idea of not jumping through hoops to have kids of my own. Now, if things had been different and it had been possible that we would have had an "oops" pregnancy, we would have been happy to have that together. However, that was not ever going to happen. We were going to have to TRY if we were going to have children together.
Of course, there were some people who didn't know the background who would ask from time to time whether we were going to have kids, and I deflected, but honestly, most people were pretty cool about it. Even, especially, my mother! By the time I married, I was almost 38, the age my mom was when she got pregnant with me. She understands how it gets harder to take care of children when you're an "older" parent, and she also respected the fact that I was parenting in my own way in the role I played raising my stepsons. She never pestered me to have kids, and for that, I am grateful.
But anyway, over the years I came to realize that it's not necessary to squeeze a baby out of your body to play a real and lasting role in shaping young lives or contributing to society. I have huge respect for parents of all kinds, and I appreciate the respect of people who can see me as a stepparent, or my friends who are not parents at all, as people who have just as full and fulfilling lives as those who decide to have children. It's really nobody else's business, and I always wonder why others care so much about another person's decisions on whether or not to procreate. After all, if the planet is not going to overpopulate itself, some of us surely need to NOT have kids, right?