Claire North is sometimes the envy of other parents in her Silver Spring neighborhood, and it's not because of her house or her car or even her child's report cards. The reason is North's easygoing lifestyle, compared with many other parents'. And the pace is possible because North has only one child, a 4-year-old son.

"We have so much freedom that other people don't have," she said. "We go out to restaurants. We go on Metro at the drop of a hat. We go away overnight with or without him. We can leave him with another parent. We just go, and they're envious of that. Also, I know I don't have to worry even if college is $50,000, whereas if I had a couple kids by now, I'd be back to work, and I'd be crazed about it."

Likewise for Richmond resident Robin Schroeder, who had her only child six years ago and finds that playing taxi driver for one child's soccer games and birthday parties is more than enough.

Years ago, North and Schroeder might have felt isolated. But today, they have plenty of company: Each woman has three or four close friends with just one child.

Once considered rarities or lonely creatures, only children now are nearly commonplace and much more accepted, especially in metropolitan areas such as Washington, where many women delay childbirth or try to balance a career with motherhood.

The percentage of women nationwide who have one child has nearly doubled in the past 20 years, based on annual surveys of women 40 to 44 years old, who are likely to be done with childbearing. In 1980, 10 percent of women in that age range had one child, according to the National Center on Health Statistics. Today, nearly 19 percent of that age group has just one, and the rate is even higher--22 percent--among "non-white" women. The survey does not offer a breakdown by income or region of the country.

Some of those families have one child because nature intervened, but a growing number of women say one child is their ideal. According to the Census Bureau's Birth Expectation Survey, the percentage of women ages 18 to 34 who plan to have one child has increased slowly but steadily, from 12.7 percent in 1985 to 13.9 percent today. No recent figure is available for Washington area women.

The reasons for the trend are many, say sociologists, psychologists and the parents themselves. Women are older today, on average, when they marry and when they have their first child. That delay can set the stage for secondary infertility--a woman's inability to become pregnant a second time--or a decision to stop at one.

"What we call the opportunity costs of having a child are greater now," said Harriet B. Presser, a mother of one and a sociologist at the University of Maryland at College Park. "You're losing more in the labor market by dropping out, even temporarily. . . . Another factor is that women's sense of entitlement to time of their own is getting greater. By postponing first birth, you get a sense of entitlement to time being yours as opposed to somebody else's."

Busy, two-career couples sometimes decide that one is the right number for their lifestyle, as did Schroeder, a self-employed marketing consultant, and her husband, a police officer. Friends had told them that the second child doesn't double the parenting work; it increases it exponentially.

"That was kind of frightening to me," Schroeder said.

Just as frightening are the economics of child rearing. Last year, the U.S. Department of Agriculture estimated that a family with an annual income of more than $60,000 would spend $228,000 to raise a child, and that figure didn't include college.

"I'm looking to support more than my immediate family. I'm concerned about taking on more," said Jeanine Hull, a D.C. mother of one who made her husband vow when they married that he "would never bug me about children, and that we wouldn't have any."

She changed her mind, she said, but one is enough. Gabriel, 6, attends a private school, travels with his parents to Europe and someday, Hull hopes, will go with them to Africa. Those things are affordable because he's their only child.

Despite the stereotype, such opportunities don't necessarily spoil only children, parents say.

"He feels more supported than spoiled," Betsy Foley, of Kensington, said of her son. "Having one is a piece of cake."

Nonetheless, parents say they take extra steps to make sure they don't overindulge their child.

"I want to instill in her that she's very important to me, but the whole world doesn't revolve around her," said Arlingtonian Gail Schatell, mother of a 6-year-old girl. On the flip side, she said: "I find it's so nice to be able to focus on her when I want. It's so gratifying."

Children don't always find it gratifying, however. Some parents of singletons say they struggle with what to say when their child prods them for a sibling.

Jane Annunziata, mother of an only child and a clinical psychologist in McLean, didn't know what to say, which is what led her to co-write a children's book on the subject last year. "I thought, 'Gosh, if I'm struggling . . . what are other people doing?' " she said.

In her book "Why Am I an Only Child?" Eudora, a purple rhinoceros child with no siblings, learns that "all families are different," that "every family has its own right size" and that there are advantages to her family's size, such as not having to share toys and getting extra attention.

"I feel special!" Eudora exclaims at the end.

Many parents acknowledge that they have to walk the same path Eudora did, coming to peace with their decision.

"I like to think I don't feel guilty about it, and part of me doesn't and part of me does," said Alexandria resident Bonnie Lilienfeld, 39, who has a 4-year-old son, Aidan. Her husband, Claudio, has an "idyllic relationship" with his brother, she said, and was initially disappointed when she said she couldn't bear to repeat the physical complications of her pregnancy.

"It's a complicated decision," she said. "We spend a lot of time thinking about it still."

Psychologist Carl Pickhardt, author of "Barron's Keys to Parenting the Only Child," said such ambivalence is common.

"Everything is double-edged," he said. Only children tend to be treated like adults, which makes them well-spoken but often insecure, because they compare themselves to adults. They learn to speak up for themselves, but that quality is not so attractive in adolescence--a phase considered even tougher with only children, Pickhardt said.

Turning the tables on the traditionally pessimistic outlook toward only children is one goal of the founders of the World Wide Web site www.onlychild.com and its sister magazine, Only Child. Charles and Carolyn White--parents of one--launched the ventures four years ago and have been overwhelmed by the response.

Each quarterly issue of the magazine has tips from psychologists, an advice column--topics have included suburban discrimination, adolescent aggravation, living in regret--and profiles of only children such as actors Cary Grant and Lauren Bacall and Federal Reserve Chairman Alan Greenspan.

The 32-page magazine has 1,000 subscribers, Charles White said. The Web site gets about 1,200 hits a day and as many as 30,000 after a mention in other media.

The Whites' venture no doubt is aided by a typical characteristic of only child parents, according to Pickhardt: They do every last thing they can for their child.

"They put a lot of pressure on themselves, because they're not going to have a chance to parent again," he said.

Pickhardt added that many of the only-child stereotypes are disappearing. As only children become more common, they are better understood.

"All it takes to make a family," he said, "is a parent and a child."

CAPTION: Claire North, left, and Betsy Foley talk in Foley's Kensington back yard while their children--Con Foley, left, and Michael North--play. "We have so much freedom that other people don't have," North says of her one-child family.