Ms. Yñiguez, 35, a department store cashier who now lives in Redwood City in the San Francisco Bay area, said she could not imagine having more than the three children she has, not if she wants to educate them and ferry them to soccer games, dance lessons and play dates. And she does not want to diverge from the goal that brought her to this country.

"You need to work to get ahead, and with children it's too hard," she said.

Her decision to stop at three has made her part of a trend that is catching some demographers by surprise.

Hispanic women are choosing to have smaller families, in some cases resisting the social pressures that shaped the Hispanic tradition of big families.

Hispanics became the country's largest minority partly because they had the highest fertility rate among the major ethnic groups. But that fertility rate is on the decline as more women work at a younger age, achieve higher levels of education and postpone marriage, all of which affects when they will give birth and how often, sociologists who study Hispanic trends say.

In California, with the largest Hispanic population, state demographers recently scaled back their population projections for 2040 by nearly seven million people, citing as one major reason the continuing drop in the fertility rate of Hispanic women to 2.6 children per woman in 2004, from 2.8 in 1997 and 3.4 in 1990. Nationally the fertility rates for Hispanics dropped to 2.7 children in 2002 from 2.9 in the early 90's (although the rate has risen in some states with newer immigrant populations, like Georgia and North Carolina).

Demographers say the decline is significant because of the size of the Hispanic population - about 40 million - and the implications for long-term needs tied to population growth. In California, for example, the increase in the school-age population will not be as striking as was anticipated, some said.

"It means Hispanics, men and women, are increasing their options of what kind of life they're going to have," said William Frey, a demographer with the Brookings Institution in Washington who studies race and ethnic change. Family may still come first, Mr. Frey said, but compromises may be necessary. Now, he said, "they're like everybody else."

Assimilation into the American lifestyle is certainly fueling the trend. Studies by the Public Policy Institute of California, a research organization in San Francisco, show that American-born Hispanics have a much lower fertility rate (2.2) than that of immigrant Hispanics (3.1) in the state.

But the studies also show that the rate for immigrant women has dropped 30 percent over the last decade, reflecting birth trends in home countries like Mexico.

Isis Moran, a 19-year-old from Santa Ana in Orange County, said she planned to have two or three children, even though her Mexican-born mother, Viviana Abalo de Moran, 42, warns her she might regret having that few. At her daughter's age Mrs. Moran was already married and pregnant with the first of her five girls. She is one of 11 siblings, all of whom, she said, had to work in the fields in Mexico and most of whom did not get past elementary school.

"I asked my mom, 'Why so many children?' " said Viviana Moran, who by 14 had left for California. "It was ignorance. They didn't know how to take care of themselves in those days. My mother started taking the pill after the 11th child."

Mrs. Moran, a nurse assistant, said she had five daughters while trying for a baby boy to please her husband. But she likes the idea of a full dinner table at Thanksgiving and Christmas, she said, and warns her daughters to think "how you'll feel with a table with just two children."

Her daughter, a sophomore at Cornell University who hopes to pursue a career in politics, said she would feel just fine. "It's not that the family is not a priority," Ms. Moran said. "It's just that there's other things involved. If I'm going to have the profession I'm looking into, it would be rough on a big family."

The resolve to limit their families has led some women to an extreme choice. Digna Campos said she would have been happy with only one child, her 9-year-old daughter. But when her contraceptive - the patch - failed, she found herself pregnant with her second baby. Last month Ms. Campos, 35, joined seven other Hispanic women attending a class on female sterilization at Kaiser Permanente Los Angeles Medical Center. The women watched a graphic video in Spanish that showed the actual surgery and a dramatization of its pros and cons.

"It's like saying goodbye to a part of myself," a woman in the video said in the melodramatic style of a telenovela.

There was not a wet eye in the room. Afterward the women, including Ms. Campos, signed the form consenting to a tubal sterilization after her second child is born.

"You want the best for your children, and I can give everything to two," explained Ms. Campos, a lobby attendant at a Los Angeles hotel, who emigrated from El Salvador in 1988. "More than two would be too difficult."

In their quest for smaller families, Hispanic women say, quality of life is paramount for those who came from big families themselves and felt crowded and neglected. Hispanics still have higher fertility rates than non-Hispanic white and black women and other groups, and outreach workers say many women still contend with machismo and social and religious pressures to procreate.

Some agencies said that Hispanic women must still contend with poor access to health care because of the lack of health insurance or bilingual services.

"Hispanics don't see health care providers as often as other women of color," said Silvia Enriquez, the director of the National Hispanic Institute for Reproductive Health in New York. "The structural barriers of not having health insurance and culturally appropriate health care are still there."

But the cultural and religious norms that once dictated larger families have also evolved. The Roman Catholic Church, for instance, opposes birth control, but few priests would press the issue from the pulpit or in the confessional, given the overwhelming rejection of such doctrine among Catholics, said the Rev. John Coleman, a sociologist and professor of social values at Loyola Marymount University in Los Angeles.

"Most Catholics practice birth control, and they don't see it as a stumbling block to being Catholics," Father Coleman said. Organizations like Planned Parenthood note that Hispanics today have more access to a wider variety of contraceptives, and they are using them.

And while outreach workers for Planned Parenthood say they find Hispanics who still believe that having children helps keep their men faithful, the men have become more receptive to family planning.

On a cold Monday morning in November two of the outreach workers, Maria Lam and Delmy Cetino, were at the Wilshire Union Day Laborer Center in Los Angeles, demonstrating the use of a condom to about 30 construction workers waiting for jobs.

The men listened with a mixture of curiosity, amusement and embarrassment, but many said that they would have to limit the number of children they have.

Luis A. Santos, 28, said his girlfriend wanted to be sterilized after her third child is born, in a few months, even though he wants more.

But David Saenz, 27, said he and his girlfriend had agreed that they would have no children for now. Finding work is tough, he said, and "it's O.K. for me to go hungry but not the children."

Even among the Hispanics who have decided to limit the size of their families, some speak almost wistfully about the "Brady Bunch" ideal, if they could afford it or if times were different.

Isis Moran said she confirmed there was a good side to being part of a big family when she went off to college and moved across the country. For a whole summer she had a room of her own. But instead of enjoying it she felt lonely.

She missed her sisters, who were her close friends. And she appreciated the "pretty neat" experience of pitching in with the younger ones, changing their diapers, teaching them how to ride a bike.

"In being independent, I also learned how important my family really is to me," she said.