More American women not having children: Report

More American women are choosing not to have children than three decades ago, according to a new report.

Nearly 20% of older women do not have children, compared to 10% in the 1970s, the Pew Research Center said.

"In recent decades, social pressure to play traditional roles has lessened in a broad variety of ways and there is more leeway for individual choice. This could play a part in lowering pressure for people to get married and bear children," said D'Vera Cohn, a co-author of the report.

"Women have more options than in the past to build strong careers and to exercise the choice not to have children," she added in an email.

The findings in the report are based on data from the Census Bureau's Current Population Survey.

Cohn said another reason for the increase is that children are seen by some as less important for a successful marriage. A 2007 Pew survey found that 41% of adults said that children are very important for a good marriage, down from 65% in 1990.

One in five white women ages 40-44 were childless in 2008, compared with 17% of black and Hispanic women and 16% of Asian women. Between 1994 and 2008, the childlessness rates for black and Hispanic women rose by almost a third, much higher than the 11% increase for white women.

Education also seems to be a factor in a woman's choice to be a mother. The more educated women are, the higher the childless rate is.

For women with a high school diploma, the rate is 17%, compared to 24% of women with a bachelor's degree. But the childlessness rate has decreased for women with advanced degrees from 31% in 1994 to 24% in 2008.

"Economists will tell you that more educated women have more to gain economically from prioritising their careers, compared with less educated women," said Cohn.

"The most educated women also tend to marry at older ages and to postpone childbearing until older ages more than less educated women do," Cohn said.