Never-married women still had the highest incidence of childlessness, though those rates also have declined over the past 10 years. By comparison, the childless rates have increased for those who are married or were at one time referred to as the "ever-marrieds."
"A lot of women can't find someone, or they're very picky or very educated," Corio said. "Contraception is also better. A lot of pregnancies in the past may have been accidents where they decided to keep the baby. It's also money - they think, we're not in the financial situation [to have children]."
Among the women aged 40 to 44 without children, the number of those who didn't want to have children equaled the number of those who did but weren't able to conceive, according to figures from the National Survey of Family Growth.
In 2003, about 6 percent of women in that age group were voluntarily childless, 6 percent were involuntarily childless and 2 percent didn't have children but wanted them in the future.
Along with the population changes have come shifts in attitude, with public opinion showing more acceptance of women without children, Pew Research reported. Most adults - 59 percent in 2002 - said they disagree with the statement that people who don't have kids "lead empty lives," compared to only 39 percent who didn't agree with the statement in 1988.
Similarly, a 2007 Pew survey showed that 41 percent of adults believe children are important for a successful marriage, down from 65 percent who expressed the same views in 1990.
About 46 percent of people said the trend has no bearing on society, according to a 2009 Pew survey, but 38 percent said it was bad for society -- up from 29 percent in 2007.
Read more from AOL Health:
- Pregnant at Age 50
- Women With This Blood Type May Have Trouble Getting Pregnant
- Lab-Created Ovary Makes Eggs, May Someday Help Women Conceive
Written by Catherine Donaldson-Evans for AOL Health