When Katharine Hepburn chose childlessness in the 1940s, she claimed that "I was ambitious and knew I would not have children. I wanted total freedom." Her views were thought to be scandalous. But when Oprah Winfrey admitted in 1994 to People magazine that "what it takes one on one [to parent], I don’t have," she was not pilloried but praised for understanding her own needs.

For a variety of reasons—including greater education for women, effective birth control, and later marriage—there has been a dramatic increase in the number of childless women over the past 30 years. According to the U.S. Census Bureau, in 1993 there were 34.9 million American families that were childless and only 33.3 million families with a child under the age of 18. Childlessness is about to come bursting out of the closet.

In interviewing more than a hundred childless women for my book The Childless Revolution, my goal was simply to put a face on childless women, not to make a major discovery about them. What I was not prepared for was uncovering a revolution in the making.

Childless women today are on the precipice of redefining womanhood in the most fundamental way ever. Entering the workforce was merely the initial step toward redefining women—and possibly the first toward childlessness. The advent of the pill, the legalization of abortion, and advanced education for women were essential adjuncts to this change. The move toward remaining childless, however, is more profound. For a society based on "family values," this shift is historic. At its most fundamental level, the emergence of childlessness means that women are seizing the opportunity to be fully realized, self-determined individuals—regardless of what society at large thinks of them.

Not all women without children actively choose the childless life, of course, but among those who have chosen it, I found three distinct groups: those who are positively childfree, those who are religiously childfree, and those who are environmentally childfree.

Women who are positively childfree rarely express even a flicker of doubt about their decision. They range from those who love other people’s children to those who admit to actively disliking kids. The religiously childfree are those who have made a decision to follow a spiritual path that requires them to remain childless. Women who are environmentally childfree have made a conscious decision to forgo having children for the good of the planet.

Although 43 percent of the adult female population is childless, these women—and the option—are still treated as though they do not exist. Childless women permeate our world. They are our neighbors, our co-workers, our sisters, and our best friends. But because these women do not conform to traditional roles, their existence is denied. What little knowledge we do have of childless women is based on negative stereotypes, such as the child-hating workaholic.