I'm in the minority

According to wikipedia, 82% of women between the ages of 40 and 44 are mothers in the U.S. I am 41, and not a mother. I don't plan on having children. It wasn't something I consciously thought about; my life just sort of happened that way. And, I am perfectly fine with it. I have animals and nephews that allow me to 'take care' of them.
The fact that I am not a mom doesn't enter my consciousness much, but once in awhile at our monthly dinners, I feel like I don't belong. I would say that our monthly club matches pretty closely to the 82% of the nation. Sometimes, I just feel overwhelmed by talk of kids, schools, pregnancy, etc. There is absolutely nothing I can offer in the way of experience to these conversations.
It's weird how time shifts and lives change. We've been doing these dinners (before dinners, we had bunko night) for over 10 years. When we started, I think only one person had a child. Through the years, there have been many weddings and births. Lives have completely changed for people.
Not for me. Everything in my life is pretty much the same.
So, when conversations focus on kids, kids, and then kids, I feel left out. Is left out the right word? I think I actually feel frustrated.
But, is it fair for me to feel frustrated? At a dinner of 8 to 10 women, people can talk about whatever the hell they want, right? Right. And with most of the women having a common link: being a mother, conversations will naturally veer towards the common link.
It's just weird being in the minority now when I did not make any changes in my life; by remaining the same, I became different.