With a singles boom, a baby bust and a vast increase in the number of working women, the Washington area is at the leading edge of major changes in American family structures and life styles, according to a new analysis of 1980 census data.

Compared to 13 other major metropolitan areas, Washington and its suburbs have the lowest fertility rate, the highest proportion of never-married adults, the highest percentage of working women and the second-highest proportion of households made up of unmarried, unrelated adults.

Overall, the Washington area ranked first in a composite measure of 17 indicators, showing life-style changes away from stable child-centered families to a society increasingly shaped by career-oriented adults with a wide range of household arrangements.

San Francisco-Oakland was ranked second in the report, issued today by the Greater Washington Research Center, followed by Minneapolis-St. Paul, New York and Los Angeles.

The major metropolitan areas showing the least social change were St. Louis, Philadelphia, Pittsburgh and Detroit.

In virtually all categories the Washington area was far higher than the nationwide averages, though these have shifted rapidly, the report said, since 1970.

"The same vast changes are taking place across the nation, but they are taking place first and taking place more in Washington," said demographer George Grier, who wrote the report with his wife, Eunice. "The Washington area is a leading indicator of what America is becoming."

"We've become a more adult-oriented society, less interested in children," he continued. "We want to be free longer, not tied down as much. I don't think it's throwing away all responsibility. But clearly there's a great change in the type of households we have and the things we want from government and business."

The Griers said the key reasons why the shift was greatest in Washington were the area's white-collar economy--with the nation's highest income levels and greatest concentration of professionals--and the opportunities it offers for a transformation in the role of women away from a focus on child-rearing toward careers and professional work.

Despite the changes, 81 percent of the Washington area's 3.1 million residents live in families, the 1980 census shows, and about 57 percent, including children, are in married-couple families. However, both these figures are down considerably from a decade earlier, when 87 percent of area residents lived in families and 69 percent in families with married couples.

"Families have not gone out of business by any means," Grier said. "They are still predominant. But it is the nonfamily households that are growing."

The Census Bureau defines a family as two or more related persons living together. It includes husband-wife couples and single-parent families as well as families with children and those which are childless.

Nonfamily households consist of individuals living alone, now 9 percent of the area's population and 26 percent of its households, and of two or more nonrelatives that share living quarters, either in couples or groups of the same or opposite sex. About 7 percent of area residents now live with nonrelatives, accounting for nearly 7 percent of households.

While the area's total population rose by 5 percent from 1970 to 1980, the number of people living in families declined by 2 percent.

Those in married-couple families fell by 248,529 or 12 percent, while persons in other types of families, mostly single-parent households headed by women, increased by 198,952 or 38 percent.

The number living alone rose by 63 percent, including many singles in their 20s and 30s and widows in their 60s and 70s. Those maintaining households with nonrelatives climbed by 93 percent.

Along with the changes in living arrangements there have been major shifts, the report says, in the patterns of marriage and birth.

During the 1970s there was a 2 percent drop in the 1.2 million people currently married in the Washington area, while those of marriageable age who never married rose by 31 percent and those divorced or separated soared by almost 79 percent.

Among those who had married, 16 percent were divorced or separated in 1980, compared to about 10 percent 10 years earlier.

Meanwhile, the number of children under age 18 declined during the decade by 18 percent. They now make up about 27 percent of the area's population compared to 35 percent a decade earlier.

The number under age 5 fell by 68,458 or 26 percent even though the number of young women increased substantially. As a result, the area's fertility rate dropped by 37 percent to 236 children under 5 years of age per 1,000 women aged 15 to 44. Nationwide the fertility rate dropped during the decade by 24 percent to 309 small children per 1,000 women capable of having them.

Of the major metropolitan areas in the report, all with populations of more than 2 million, Washington's drop in fertility was the sharpest and its fertility rate now is the lowest.

The Griers said the decline in child-bearing was caused partly by improved contraception and legalized abortion, but also by a vast upsurge in women who work. During the 1970s the number of women in the Washington area's labor force increased by 45 percent, far more than the modest 14 percent increase in working men. By 1980, about 62 percent of working-age women here were in the labor force.

"Many of these women are from the baby-boom generation (now in their 20s and early 30s)," Eunice Grier said. "But there's been an enormous change in their values and attitudes toward families and work. They're not working just to contribute to their family income . . . When they have children, most return to the work force as soon as they can. And there are very few of them having three children."

Partly because of its working women, Washington continued to have the highest average income for any large metropolitan area, the report said. In 1979, the year recorded by the 1980 census, its median family income was $27,815, a figure that rose to an estimated $30,000 last year.

Even though inflation has held down purchasing power, the drop in children has meant that more money is available for luxury goods and expensive housing, including condominiums, the Griers noted.

"Adults are spending a good deal more on themselves--better clothing, health clubs, good restaurants, better housing," George Grier said. "They don't spend so much on children." Local governments, he said, are spending a smaller proportion of their budgets on schools and much more on public transit for working adults.

"There are pluses and minuses in all these changes," Grier said, "more opportunities for adults but probably less care for children, more freedom for individuals but more loneliness and insecurity . . . Whether you like it or not, I think we're making a permanent change."