The most rapid rise in female employment in this decade has taken place among married women, especially those with children under 6, according to a new study that describes a marked shift in attitudes about "women's place."

Women still tended to drop out of their jobs while their children were young during the '50s and '60s.

But in the 1970s, the employment rate for women aged 25 to 34, the prime ages for childbearing and early child rearing, soared by more than half, from 43 percent in 1970 to 65 percent last year, according to the Washington-based Population Reference Bureau, which assembled the information.

Forty-five percent of married mothers or preschool children under age 6 were working in 1980, compared to 12 percent in 1950.

By March, 1980, 25 million wives, or half of all married women living with their husbands, were working or looking for work.

Working women were putting in an average of two hours and 23 minutes a day on housework, compared to 25 minutes a day for married men, according to the report. Still, time-budget surveys show that this double duty had eased a bit since the mid-60's.

Over half of all women 16 and older now work, and an estimated 68 percent of them work because of economic necessity, one economist concluded.

Still, two-earner families may pay more Social Security tax and receive lower retirement benefits than one-earner families with comparable incomes, according to the report.

And one study showed that, after taxes and other costs were figured in, the two-earner family needs about 30 percent more income than the one-earner family to maintain the same standard of living. m