Cameron Diaz recently spoke to Esquire about her decision to opt out of mommyhood, and her thoughts on the hot-button topic were refreshingly calm and real. “I like protecting people, but I was never drawn to being a mother,” she says. “It’s so much more work to have children. To have lives besides your own that you are responsible for—I didn’t take that on. That did make things easier for me.We spoke to more women about their reasons for not having babies:Sharon, a 30 year-old writer for an art auction house, left her ex-husband because he wanted kids and she didn’t. She has no regrets.She offers many of the usual reasons people give for not wanting children—career, finances, bad genes, crazy parenting they don’t want to repeat and the overpopulated planet—but the simple truth is that it wasn’t a priority. “And if you’re not totally sold on it, it makes no sense,” she says.Now listen to Samantha, 26, a graduate student: “I just don’t like children very much,” she says. “The idea of having such a demand on my time, attention and resources is frankly horrifying to me.”Motherhood is becoming a choice. People used to think that once a young woman was married, she got pregnant. If not, “other people would assume you were self-centered, or say, ‘I’m so sorry,’’’ says San Jose psychotherapist Margaret Cochran. Now clear-eyed women like Diaz, Sharon and Samantha aren’t afraid to say no to babies. “I’m surprised at how many women in their thirties aren’t even talking about it!,” says Ellen L. Walker, the (child-free) author of “Complete Without Kids: An Insider’s Guide to Childfree Living By Choice Or By Chance“, and a practicing therapist in Bellingham, WA.MORE: Young and Divorced: How To Bounce BackTo become a mother is your single biggest decision, more important than your choice of husband or career, Walker argues. She approvingly describes one woman she interviewed for “Complete Without Kids” who spent two years tailing along on family vacations and attending kid activities with the mothers she knew in order to make her choice. Careers and relationships can be revised but children are for life and no, you can’t “have it all” and “be a good wife and mother and daughter and friend and have hobbies and exercise,” Walker says. “Something has to go.”As the population of non-parents grows, a kid-free life seems less odd. In 2008, about 18 percent of women ages 40-44 weren’t mothers and were hitting the end of their child-bearing years, up from 10 percent in 1976, according to a Pew Research Center study of Census figures. And among child-free married couples including a woman of childbearing age, about 20 percent say they are voluntarily planning to stay that way. Kelly Short and her husband, both turning 40 this year, are a striking example of the kind of a couple who seemed perfect for family-building, but the time was never right. College sweethearts, they married at 26, moved to the Boston suburbs, and kept talking about “when we would be ready” for kids. But by 35, her husband was busy traveling as a partner in an accounting firm and Karen, a speech pathologist for small children with severe handicaps, didn’t want to quit or add childcare. Her work made her acutely aware of the risks of giving birth at older ages. So at 39, she decided to embrace their child-free life and start a meet-up group for like-minded couples.Many such couples want freedom, perhaps for risky careers or just fun. Two years ago, Madeline, 40, took a 50 percent pay cut to leave a partner-track corporate law firm job to work at a nonprofit. Her husband is a risk-taking entrepreneur. “I want the freedom to do what I want. The thought of a child relying on me is stressful,” she says.Madeline also thinks she’ll have a better marriage without kids. “We have a lot of time for each other,” she says.Walker, too, stresses that she and her husband are friends and playmates. She hadn’t wanted children, but when she married in her mid-forties, she began to wonder if she was missing out. “I looked at his first wife and thought, she’s the real wife, and I’m just the playmate,” she says. But eventually she realized that “He and his first wife were more like business partners because they were so busy.” Her brief period of regret ended.Like Walker and her husband, couples without kids, observers say, are more likely to focus on their relationship. When Laura Carroll interviewed 100 child-free couples married at least 10 years for her book “Families of Two“, she found that they tended to have strong, shared interests like travel and antiques and to put those interests in the center of their lives. Cory Jones, who co-founded with his fiancé dinklife.com, a website dedicated to “dink” couples (dual income no kids), agrees, adding, “When you think your life is fantastic, it’s a risk to change it.” Short launched a travel planning website, CWKtrips.com for other similar couples.QUIZ: Happiness QuizSome people focus on political reasons. As Jane, a 41-year old nonprofit executive, points out, “You can do everything right and still have a child that might be a burden or a danger to society. I don’t want that responsibility. Besides, there are so many unwanted children I don’t feel a tremendous need to pass on my genes.”Column: Solving Your Relationship ProblemsVera, a 43-year old health administrator, assumed she would have children until she watched her younger sister cope with a baby at seventeen. She saw “there is a lot of drudgery with child care that isn’t really mentioned. Even playing with them at times can get tedious and exhausting. Also, as an African-American, I’m aware that black single mothers are stereotyped as dumb, lazy and/or that they are all on welfare. I didn’t want to become a mother unless I had a ring on my finger. Since there is no guarantee that I would ever get married or stay married, I didn’t want to become a statistic.”For those mulling over doubts, psychologists suggest flipping the question to ask, “Why have kids?”“Some people want kids because they think they’ll get a great reward: ‘I’ll finally have someone who loves me,’” says Cochran. “Or they might think it will make their spouse love them again, fix the marriage. Some people think having children makes them an adult or will increase their status. Even if you get those things, you won’t be happy with the price. And that’s not okay to do to the kids.”Parents often say their children bring a kind of joy you won’t understand until you’ve experienced it, which makes the childless feel left out. “Most people wouldn’t give up their children,” says Raleigh, North Carolina psychotherapist Mardy Ireland, author of “Reconceiving Women: Separating Motherhood from Female Identity.” However, “the idea that everyone thinks it’s the best thing they ever did is a romanticization,” she says.It’s true that birth, breast-feeding and continual responsibility are powerful physical experiences that change us—ideally to be more mature and loving. The hopeful assumption, Ireland says, is that everyone can grow into the capacity to be good parents. In fact, she says, “You may resent them or you may not have the energy or you may not like certain things about your child.”But that’s rarely what one hears from the anxious family. Alice, an outgoing generous 31-year old executive assistant, loves to bake and give presents. Her mother wants her to have kids. “She knows I will love it and knows I will be a good mom,” Alice says. Yet she says she’s never had “that feeling that tells women they want kids.”MORE: Go It AloneAlice has plenty of children in her life, like many of the child-free-by-choice crowd, who tend to be active aunts, godparents and volunteers with children. They nurture in other ways as well, through caring for other family members, patients or younger colleagues. “All of us need something to nurture,” Cochran says. “There are lots of ways to express love. In our culture, we focus on having kids. But it’s rare that I have patients who regret that they didn’t have children. Often upon reflection, they realize that there were other ways that they nurtured.”Although Alice’s husband is happy, his mother complains about “how sad she is she won’t have grandchildren while she’s still young and how she just can’t even believe that we wouldn’t want kids,” Alice says. Other people tell Alice it’s “a waste” of her nurturing talents not to have kids. Still, Alice is holding her own. “I just think they’re all brainwashed!,” she says.