Ursula Burns joined a rare breed when she took command of Xerox Corp. (NYSE: XRXNews) in July 2009: She became just the 22nd woman ever to run a Fortune 500 company.

What isn’t so rare is that she’s a mom. In fact, all but two members of the female CEO elite at big U.S. businesses have motherhood in common. The finding, uncovered by author Douglas Branson, throws a curveball at the “mommy track” idea, and the belief that women must choose between being mothers and reaching the corner office. “You have a better chance of being a mother and becoming a company CEO than you did 15 years ago,” says Mr. Branson, a University of Pittsburgh law professor whose new book, “The Last Male Bastion,” examines female chief executives.

At present, there are 12 female CEOs of Fortune 500 companies, 11 of whom are moms. Campbell Soup Co. (NYSE: CPBNews) late last month announced its next CEO will be Denise Morrison, a senior executive with daughters aged 29 and 31. Xerox’s Ms. Burns, who spent decades moving up at the company, has a 17-year-old daughter and 21-year-old stepson. Her predecessor, Anne Mulcahy, has two offspring as well. All three executives declined to comment for this story.

The prevalence of mothers in the corner office hardly means women’s careers aren’t disadvantaged by parenthood. Men with children are more likely to rise into management than women with children in most major industries, including retail, health care and financial services, according to a U.S. Government Accountability Office report on the gender gap released Sept. 28. The 79 cents manager moms make for every dollar earned by manager dads “has not budged since 2000,” the report concluded.

The fact most big-company female CEOs have children may just state the obvious—that the highest achievers can handle big challenges, suggests Claudia Goldin, a Harvard economics professor who has studied earnings penalties linked to motherhood.

Still, a look behind the scenes reveals some of the usual work-family trade-offs. In a management career crammed with frequent business trips, “I didn’t make it to every single sporting event of my two children when they were growing up,” says Stephanie Sonnabend, CEO of Sonesta International Hotels Corp. (NASDAQ: SNSTANews) since 2003. “You make it up in other ways.”

Her daughter and son, now 23 and 21 years old, accompanied her on business trips to Curacao, Egypt and Peru, she says.

Highly successful CEO mothers also often enjoy extensive support from their husbands, some of whom decide to skip the fast track. Gregory Ciccolo, Ms. Sonnabend’s husband, was a promising tenor when he dropped plans to join a small European opera company for six months in 1994. Both say she requested his sacrifice because she needed to travel more following a Sonesta promotion.

Mr. Ciccolo recalls feeling disappointed. He soon stopped singing professionally, and now runs a small recording studio. “Have I been able to replace the possibility of singing around the world? Not really,” he says. “In terms of tradeoffs, this was fairly big league.” But, he adds, “we were going to be a lot more financially secure with her job than mine.”

Mary Dillon, who since June has been chief executive of U.S. Cellular Corp., was a brand manager at Quaker Oats Co. when she gave birth for the first time in 1990. She says her husband, Terry, quit his job as a biochemist after the second of their four children arrived, so he could parent full time.

The setup, still in effect, offered “the flexibility on schedule and travel that has been required for my various positions,” Ms. Dillon continues. Her children range in age between 11 and 20.

Patricia Woertz was a rising oil-industry star when she and her husband, a logistics consultant, agreed her career would take priority, according to an Archer-Daniels-Midland Co. (NYSE: ADMNews) spokesman. The mother of three was divorced by the time she began leading the grain-processing giant in 2006. Ms. Woertz declined to be interviewed for this story.

Several CEO moms say they advanced partly because they created strict boundaries between work and home. “If you can compartmentalize, you can focus,” explains Yahoo Inc. (NASDAQ: YHOONews) Chief Executive Carol Bartz, whose three children are aged 21 to 31. “You plan not to have guilt.”

After work, for instance, “When you walk in the door, you should be ready to say, ‘I am home now,'” and not check email until later, Ms. Bartz says. She joined the Internet concern in 2009 after leading Autodesk Inc. (NASDAQ: ADSKNews)

A number of women at the top say they drew on their experience as parents when climbing the ladder at the workplace. “I learned plenty about how to be an effective executive from raising my children,” Ms. Dillon says. When she served as global marketing chief of McDonald’s Corp. (NYSE: MCDNews), she drew on her experiences as a mother of four to push a world-wide expansion of healthy menu items, such as fresh carrots.

Ms. Bartz—famously combative—says parenthood taught her the value of picking battles at home and work. “If you discipline children on everything, they don’t know what’s important,” she observes. “Not everything that happens in a company is priority one.”

Other CEO moms found that child rearing reinforced the importance of setting clear expectations. “Being consistent is the most common trait in parenting and managing,” says Laura J. Sen, head of BJ’s Wholesale Club Inc. (NYSE: BJNews), a warehouse retailer. She has a 20-year-old son and 22-year-old daughter.

Based on their parenting roles, some female business chiefs have sought to ease staffers’ work-family conflicts by introducing perquisites such as “flex-time” and sick-child facilities.

When Janet Dolan ran Tennant Co. (NYSE: TNCNews), a maker of industrial-cleaning products, she rarely summoned her management team on short notice for routine meetings past 5 p.m. Last-minute late sessions with Tennant’s highest boss years earlier sometimes caused child-care problems for the executive mother.

“I went to the CEO and said, ‘This might hurt my career. I can do anything on 24 hours’ notice. But it’s very hard to do anything on one hour’s notice,'” Ms. Dolan says. He agreed to try to give longer notice.

Ms. Dolan’s seven-year CEO stint ended in December 2005. Her sons currently are 28 and 25 years old.

Similarly, BJ’s lacked employee wellness and weight-loss programs before Ms. Sen became its first female CEO in 2009. Thanks to her two kids, she says she tends “to have a more maternal view in terms of how we treat people.”

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