It's been about five years since anyone asked me, "Why don't you have kids?"

"Just lucky, I guess," was my response then (it was a kid who asked me), and my friends and colleagues know it's a non-issue, like you wouldn't ask Woody Allen if he'd like to go camping.

The subject has been in my thoughts, though, ever since I realized that I'm about to turn 45, which means that, not being a celebrity, my chances of reproducing are now Olsen-twin thin. The realization that my fertility was a closed issue made me feel a bit like I did when they retired the Concorde: It wasn't likely I'd ever use it, but it was nice to know it was there.

Now if this were a movie, this would fling me into crisis mode -- I imagine Sandra Bullock having a comical panic attack to bouncy-but-urgent music and hatching a crazy plan to go the turkey-baster route with her gay BFF (played by Matt Damon). Of course, there would be happy endings all around, including an infant so cute she would make a basket of kittens look like Keith Richards.

But I didn't panic. I felt relieved, and I actually enjoy my friends' kids more now that the threat of motherhood has passed.

I had occasional baby cravings in my 20s and 30s but curbed them like you would a yen for chocolate or cigarettes. I never wanted kids the way some women do and I decided I wouldn't have one unless I got really rich, and since I didn't, I didn't.

Money plays a part in a lot of women's decisions. The U.S. birth rate recently dropped by 2 percent, Time magazine says, possibly because women are worried about having kids in this economy; it costs about $221,000 to raise one for 17 years (sadly, though, the story says, the economy is also making some of them skimp on contraception).

So, done. Curtain. And now a moment to stretch my legs before starting the last act.

Wanting kids isn't just the social norm, it's said to be a biological imperative, the only supposed "duh" of evolution, so I know my lack of sentiment isn't especially mainstream. I listen to people rhapsodize about parenthood, that it's so fulfilling and the greatest job in the world. And good for them -- the more happiness in the world, the better.

Then I see parents at Target -- with one kid screaming in the cart, one screaming in their arms -- looking as blissful as a cat in a dryer. And I remember to take my pill.

Maybe because I was raised in the '70s heyday of feminism, or maybe ambivalence toward breeding is innate (Madelyn Cain's 2001 book, "The Childless Revolution: What It Means to be Childless Today," touches on the Mest gene in mice, which seemed to determine their levels of maternal behavior), but I never felt fazed by social pressure in my decision.

Now, in the interest of people who are made to feel defensive about their choice to be childless, and those who put them there, here are "Nine Things People Say When They Hear You Don't Want Kids" (and ways I've found to counter them).

• Aren't you worried about ending up old and lonely?

No. When Mel Brooks, playing the 2,000-year-old man, joked that "I have over 1,500 children and not one comes to visit me on a Sunday," he had a point: There's no guarantee that kids will be there for you in your old age. Plus, a University of Florida study has shown that the idea of the lonely, childless senior is flat not true. There's no higher rate of depression or loneliness among childless seniors. As for those seniors who did have kids, it was how well they got along that mattered, not just the fact that they were family.

• "But you'd have such great kids!"

Thanks! But that's what everyone thinks! You know damn well they're not all right!

• "But you'd be such a great mom!"

That's nice, dear ... have a cookie. While some people simply adore kids, others of us are better at providing wise Mrs. Garrett-style comfort. If you're a good listener, there are already plenty of kids and adults who could use your empathy. Indeed, what would any of our parents have done without outside support?

• "Don't you want a family?"

I was raised in a family. That was plenty. Seriously, some people just don't function well in traditional families, which are like albums -- there are only two tracks you like, but you have to buy the whole damn record. Some of us just work better a la carte.

• "But they're so cute!"

This is a topping good reason to buy a Tinkerbell T-shirt, but to bring a whole new person into existence?

• "But it's natural."

It's amazing how selective our society is about "natural" things we promote versus ones we scowl at. Nudity is natural -- and banned. Hunting is more natural than shopping, but most people wouldn't kill a pig to get a Baconator.

• "It's a woman's greatest achievement."

Producing a spin-off could well be the greatest achievement of a lot of people, but just because your contributions don't get diaper rash doesn't mean you haven't made any.

Some notable childless achievers: Jesus Christ, Julia Child, Oprah Winfrey, George Washington, Amelia Earhart, the Dalai Lama, Dr. Seuss, Margaret Mitchell and Helen Mirren. Ms. Mirren was traumatized by an educational film on childbirth as a teen, saying: "I haven't had children, and now I can't look at anything to do with childbirth. It absolutely disgusts me."

• "You'll change your mind."

Now that I'm old, no one can say this to me anymore, but if anyone says it to you, Grasshopper, just return their condescending smile and say that one day they'll change their mind about their partner, career choice, spiritual predilections or any other extraordinarily personal element of their lives. See how they like it.

• "You should have at least one of your own."

This is one of my favorites, as though kids were canapes or raffle tickets that would be gone by the time the party is over instead of people who require care, feeding and lots and lots of things.

"When I see babies, not only do I see the beauty, joy and miracle of life, I also see nappies, landfill waste, vast amounts of food and money needed, and a very shaky, unpredictable future," Joanna Benn once wrote for the BBC Science & Environment blog. She now works for the United Nations Environmental Program and notes U.N. projections that "the world population will nearly stabilize at just above 10 billion people after 2200."

Overpopulation is the greatest threat to our environment, according to a recent survey of professors at State University of New York College of Environmental Science and Forestry. In a story in Science Daily, systems ecologist Charles Hall called it "the only problem."

The choice of whether to have kids is such an intensely personal one that it seems weirdly disproportionate to literally put the weight of the world on one's shoulders when considering it; it's at least self-satisfying to know that my choice was a green one, albeit by accident.

Finally, you have to be an optimist to have kids, and I'm more your neurotic emotional claustrophobe. At least I know it; I also know, unshakably, that I made the right choice.

And choice is what it comes down to in the end -- a simple matter of to each his own, without either side passing judgment on the other for the most important and personal decision of all.

Cartoonist Rob Rogers does "Rob's Rough," an early look at his work and his creative process, exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.