Unmarried men and women who live together are nearly as likely as married couples to be raising children, according to a census report to be released today.

The report also includes the government's first numbers on gay families, showing that one-third of lesbian couples and one-fifth of male couples counted in the 2000 Census have children at home.

The figures reflect not only the increasingly common decision among unmarried couples and gay couples to live together but also their decisions to raise children together. And for now, the statistics say more about the lives of adults than the experience of childhood in America: Because of the greater number of married couples, the number of children living in those households is still much higher than in unmarried and gay households. About 25 million married-couple households include children, more than 10 times the 2.3 million households of unmarried and gay couples with children.

Still, the proportions are striking: Nationally, 43 percent of unmarried couples living together are raising children, nearly matching the 46 percent figure for the nation's married couples. And the trend is climbing for unmarried couples, while it is becoming less common for married couples to have children living with them.

The changing shape of the American family has accompanied the enormous social evolution of recent generations, from acceptance of gays to the expectation that many couples will live together as a prelude, or alternative, to marriage. The trends that now seem common are nevertheless the source of heated political and social debate. The White House, for example, has launched a campaign to promote marriage. And court battles are being waged across the country for and against the legal rights of gays to adopt and gain custody of children.

Studies show that children of live-in couples are more at risk for behavioral and academic problems, but Urban Institute researcher Gregory Acs said that may be because their parents are often poorer and less educated than married couples, not because they are living together without a marriage license.

"Kids in single-mother families tend to do worse than kids in married-couple families, and kids who live with cohabiting parents fall in between," said Acs, who has written extensively on the topic.

The District falls below the national average in its share of couples with children, whether married or unmarried, which experts said is typical of cities. In Maryland, male gay couples are more likely to have children than they are nationally, and in Virginia, they are somewhat less likely. Maryland and Virginia roughly match the national average for the share of lesbian couples with children.

For Silver Spring resident April Turner, practical considerations have kept her from marrying. She lives with her two children and their father, her partner of 11 years. They are not married, she said, mainly because the tax credit she receives on her income as a day-care worker would vanish if she had to include his income as a letter carrier. But in all other ways, she said, they consider themselves a married couple.

"We share credit, we share debt," she said. "Everything is shared except the marriage license."

Her family is not happy that she does not have a wedding ring, she said, and "I feel it every time we get together for a reunion." As for her children, it "has never been an issue," she said.

Such a living arrangement is particularly common in three states -- Mississippi, New Mexico and West Virginia -- where a greater proportion of unmarried-couple households are raising children than married-couple households, the census figures show. The South has the highest share of unmarried-couple households with children and the lowest share of married couples with them.

Demographer Martin O'Connell, co-author of the Census Bureau report, said places with high unmarried birthrates also tended to have high rates of unmarried couples with children. "When one thinks about a child born out of wedlock, the typical picture is the child living alone with the mother," he said. "What the census data show is very substantial cases of unmarried partners."

University of Wisconsin demographer Larry Bumpass says half of all children today will spend some time in a household with unmarried parents. In many of those cases, he said, the period won't be a lengthy one because most of those couples will either break up or get married within 18 months.

The figures for gay households were only for those couples who told the census they were unmarried partners, and did not include gay men and lesbians living without a partner.

Gary Gates, an Urban Institute researcher who is completing a book on the nation's gay population, said he is not surprised that a gay mecca such as the District does not have a large share of gay couples with children. That is because, like many other cities, it is not overflowing with children from other types of households. Nor was he surprised that in socially conservative states such as South Dakota and Utah, more than 40 percent of lesbian couples were raising children, far higher than the national average.

"Gay couples with kids act like other couples with kids in the way they distribute geographically," he said. "Gay couples without kids are not that different from [other] people without kids."