It started when the baby rolled off and under the bed when she was in the shower getting ready to go to work. It got worse when the nanny couldn’t figure out how to e-mail her a photo of a nasty cut on her toddler son’s chin.

Then, when she was passed over for promotion for the second time because her boss didn’t think she could handle the job and her “family responsibilities,” Jennifer Folsom, an Alexandria consultant with an MBA from Georgetown, had had it. She quit, joining a small but persistent stream of educated, upper-income women who drop out of the workforce when they find they simply can’t have it all when it comes to work and family.

But Folsom didn’t opt out for long. She joined a fledgling recruiting and placement company and turned her prodigious energy toward helping mothers like her to “opt in” — to find fulfilling work in their own time and on their own terms.

With names like Momentum Resources, 10 Til 2, On-Ramps and Flexforce Professionals, these firms are at the forefront of a growing movement to remake the American workplace not just for mothers but for everyone.

Ellen Grealish of Reston, who started Flexforce Professionals with two other working mothers after opting out of the workforce for eight years, said she has seen traditional workplaces embrace flexibility once they’ve seen how these working mothers use it so productively.

That was certainly the case for Mark Madigan, who owns IT Cadre, a software engineering firm in Ashburn. He calls the job candidates Grealish sends him his “smart moms.” And they now make up 10 percent of his workforce.

Flexibility can come with trade-offs: contract jobs with no benefits and no long-term job security, fewer opportunities for advancement or reduced hours with reduced pay.

But those in the opt-in movement say many mothers are willing to give up income if that means taking control of their schedules, and, perhaps most important, doing meaningful, challenging work in their chosen professions rather than what they see as the less interesting work of the often-stigmatized “mommy track.”

“I know mothers at law firms who felt they were relegated to doing less interesting and less time-sensitive work because of the choices they’d made,” said Lilly Garcia, a lawyer and a mother who just joined a new D.C. law practice, Clearspire, that embraces flexibility. “But here, flexibility means more interesting assignments, more challenge.”

‘I got my results’

Momentum Resources, where Folsom is now a partner, has negotiated flexible hours for hundreds of working mothers: new mothers with MBAs, whom studies have found abandon the workforce at levels higher than graduates of any other advanced-degree program. It has arranged telecommuting time for lawyers, work-from-home days for consultants or part-time hours for project managers that end when the school bus arrives.

“In a terrible market, we’re proving that flexibility really is good for both business and working families,” said Folsom, 36, who starts her workday at 5 a.m. before her children wake and often works in the evening after they’re in bed so she can spend afternoons with them. “How and when work gets done is somewhat irrelevant as we’re moving to a more results-oriented workforce. Face time is so five years ago.”

That’s what one of Folsom’s clients, Peniel Solutions, a software development company, found. “I don’t know what a typical workday is anymore,” Peniel Vice President James McGriff said. “If I get my results and you do that between 9 at night and 12 at night, why am I interested in that? I got my results.”

It’s a philosophy that has worked for Karin Lisack, another woman with a Georgetown MBA who found out the hard way that the “family friendly” policies at her company depended on the goodwill of individual managers — a common problem, several studies have found.

Peniel Solutions hired Lisack, who had been living in Arlington County, with flexible hours when she was pregnant with her second child. And when the company moved to Chantilly, it told her to work from home.

“You just have to deliver,” she said. “Once you deliver, they trust you. Then they can’t live without you.”

But a number of companies can and do live without working mothers who find they can’t juggle work and kids. By contrast, men rarely leave their professions when they become parents, researchers have found. Women without children don’t tend to quit, either.

Jane Leber Herr, an economist at the University of Chicago, analyzed a national survey of college graduates and a sample of Harvard alumnae and found that, while less than 4 percent of women without children had left the workplace 15 years after graduating, nearly 30 percent of mothers with MBAs had, followed by about a quarter of the lawyers with children and mothers with master’s of arts degrees. About 15 percent of mothers who had PhDs had opted out. By contrast, less than 6 percent of mothers with medical degrees had abandoned their practices, and many worked part time or with flexible hours.

“You would think that, given the rise in education of women, their experience, their presence in high-investment, high-income, high-value fields, the proportion of those who leave the labor force would have gone down,” said Herr, who noted that women now make up the majority in many colleges and professional programs. “What’s shocking is that it hasn’t.”

She and other economists blame workplaces that are still structured as if families don’t exist. Many companies may have family-friendly policies on the books, “but the feeling is you get penalized if you use them,” Herr said.

Liz Watson met with companies as part of the Workplace Flexibility 2010 program at Georgetown Law. What she found was simply inertia. “A lot of employers just didn’t know how to make their workplaces more flexible or didn’t know the research showing how it improved productivity.”

Momentum, Folsom said, has its best luck selling smaller and start-up firms on flexibility. Advances in technology as well as the recent recession have made some companies willing to try something new. But not all.

“We see resistance in the bigger, more bureaucratic firms that are worried about setting a precedent,” Folsom said. “In another case, we had a textbook-perfect client, but the human resources manager said they just don’t do flexibility. And she was a woman.”

That attitude reflects the tension that often exists between working mothers seeking more flexibility and their colleagues, male and female, who have embraced the model of what sociologists call the “ideal worker”: someone willing to drop everything at a moment’s notice and get to work without being encumbered by family responsibilities.

‘Our model is liberating’

Bryce Arrowood, one of Momentum’s clients, wasn’t thinking of recruiting working mothers when he envisioned his D.C. law practice, Clearspire. He wanted to create an evolved workplace for everyone.

Arrowood and his partner, Mark Cohen, spent two years and $5 million to develop a cutting-edge, Web-enabled, Facebook-like environment. Lawyers work mostly out of Clearspire-provisioned home offices, though they can book one of the handful of rooms at the firm’s headquarters on Pennsylvania Avenue to work or meet with clients. On a recent day, Arrowood was one of three people working in the elegant and spare office. The rest of the nearly 20 employees were working at home.

Clearspire does not do face time or billable hours. Lawyers set their own hours, and they leave landing new clients primarily to the firm’s business staff.

“Our model is liberating, and all kinds of people, not just working mothers, can take advantage of it,” said Arrowood, a father of three who does so himself, along with his wife, Lee, who also works at Clearspire .

For Catherine Guttman-McCabe, 42, a Harvard-trained education lawyer, Clearspire has been revolutionary. She works full-time, fairly regular hours, she said. But, working from her Arlington home, she can take a break when her girls get home from school for a little quality time, “so I’m not just nagging at the end of the day: ‘Is your homework done?’ ‘Have you brushed your teeth?’ ”

On a recent afternoon shortly before 4, the professionally dressed and coiffed Guttman-McCabe made her way up to the corner to meet her daughters at the school-bus stop.

“Mommy!” 8-year-old Abigail shouted as she threw her arms around Guttman-McCabe. As they made their way home, the girls bubbled about their day and, once they were settled in the kitchen, Guttman-McCabe fixed them a snack.

The girls prepared to do their homework and read for the afternoon and Guttman-McCabe to return to her office. Abigail hugged her again. “I was waiting the whole day for it to be the end of the day,” she said, “because I knew that’s when I would see you at the bus stop.”