If the Momazonians succeed, they will have helped engineer a major cultural shift at Amazon, where the needs of workers take a back seat to Bezos's goal of satisfying the hallowed needs of the customer. Winning a backup day care benefit could theoretically help women move up in a company where only one woman is on an influential senior management team that reports directly to Bezos.

“Everyone wants to act really tough and pretend they don't have human needs,” says Kristi Coulter, who worked in various roles at Amazon for almost 12 years and observed that many senior executives had stay-at-home wives. “You don't want to be the one to step forward and say 'I'm a mom with kids and I may not be as single-mindedly devoted to my career as everyone else.' They're all trying to assimilate to this male-dominated culture.”

In an emailed statement, Amazon said it provides valuable benefits to its 250,000 U.S. workers, including health benefits that begin on the first day, flexible paid leave for new parents and discounts at day care centers around the country.

“When creating benefits, we focus on efforts that can scale to help the largest number of individuals, and work in partnership with our employees to ensure that what we build provides meaningful support,” the company said.

The benefits of competing for talent

A tight labor market has pushed benefits to the forefront, making them a powerful recruiting and retention tool, especially in the competitive technology industry. The issue of paid parental leave, which the U.S. Bureau of Labor Statistics says is available to only 17 percent of U.S. workers, has gotten most of the attention. But the focus has started to shift to childcare, which can cost almost as much as rent or college tuition.

Amazon has several family-friendly policies. Employees can take paid parental leave all at once or spread it out over time to suit their needs. They can share it with a spouse or partner not employed by Amazon who misses work due to pregnancy and childbirth. Parents returning after childbirth can work part-time for up to eight weeks to smooth the transition. Amazon reimburses mothers traveling for work for their breast milk shipping expenses.

But many Amazon moms say a missing link is backup day care. Apple Inc., Microsoft Corp., Facebook Inc. and Google parent Alphabet Inc. all provide backup day care benefits. As millennials age into parenthood, family-friendly benefits have consistently ranked as the most coveted perks. Amazon differs from other big tech companies in that its workforce includes software engineers in Seattle as well as warehouse employees in Kentucky. Still, backup day care as a benefit is moving beyond white-collar office workers. Starbucks Corp. last year introduced the perk for baristas. Meanwhile, universal childcare is emerging as a potent political campaign issue.

Childcare is directly connected to the gender pay gap in America, a complex social issue that can perpetuate itself when families decide who should stay home from work to care for ailing children, says Katharine Zaleski, co-founder of the gender-diversity recruiting firm PowerToFly. Since most men in the U.S. earn more than women, she says, moms are more likely to stay home when children are sick since the loss of the father's income is more likely to be detrimental to the family budget. Providing backup day care helps protect women from having to choose between their children and their careers, Zaleski says.

“It sends a message about creating an inclusive workplace where women can thrive, because the company recognizes this undue burden has historically been placed on women,” she says.

Bezos holds steady

Bezos has seldom championed social issues. Amazon followed the pack in 2015 when it expanded maternity leave to 20 weeks from eight and allowed paternity leave for the first time. The company in October pledged to pay all of its warehouse workers at least $15 an hour, after presidential hopefuls Bernie Sanders and Elizabeth Warren held out Amazon workers on food stamps as an example of the need for living wage protections. Amazon in the past two months has added two women to its male-dominated board of directors, following years of criticism from activists.

Still, Bezos isn't easily persuaded to enhance benefits simply because they would help staff, according to people familiar with the company's internal deliberations. He is notoriously frugal, insisting that employees fly coach and eschewing the free meals common at other tech companies and instead giving away bananas from little kiosks around the campus. This is why, the people say, it's more effective to argue that denying the benefit hurts the bottom line by increasing recruiting costs.

Several years ago a group of Amazon employees pushed the company to provide gender reclassification surgery as part of its health care package. They initially argued that providing such a benefit would project an inclusive workplace image and help recruit top talent, according to a person involved in the campaign. Human resources advised the group to instead argue it would help the company save money, the person says. Subsidizing gender reclassification cost less than recruiting a senior engineer, making it a financial issue rather than a social one. “This was never a decision about money,” Amazon said in an emailed statement. “It was a decision to do the right thing for our employees.”

Studies demonstrate that mothers continue to bear the brunt of childcare responsibilities and companies that provide day care support can reduce employee absenteeism by as much as 30 percent. That's the kind of evidence that can resonate at Amazon, but the plight of working mothers is largely hidden, according to current and former employees who spoke on condition of anonymity.

Some don't mention having children or display family photos on desks in fear of being labeled a “distracted mom” unable to tackle important projects. Others are loath to be the first to leave even though the day care facility is about to close. Some mask their obligations. The vomiting, feverish child at school becomes a “last-minute conflict” in the meeting cancellation email to co-workers. Some new mothers don't seek promotions, doubting they'd get the support needed to take on a new role. In Seattle tech circles, friends of parents taking jobs at Amazon often joke: Leave a photo at home for your children so they don't forget who you are.

A cultural issue

The company's unrelenting demands created a pattern in which men with stay-at-home wives advanced to leadership positions and women often see their careers languish or they leave, the employees say.

One former Amazon worker says she arrived at 7 a.m. each day to avoid the distracting sounds of her mostly male colleagues shooting Nerf guns and bouncing tennis balls off the wall. She was warned about the “bad optics” of leaving before her colleagues, so often stayed until 7 p.m. She spoke with HR about her difficulties and says they suggested she start looking for another job if the culture wasn't a good fit.

Many managers see “butts in seats” as a sign of a well-run department, making work-life balance a challenge for parents with conflicts, the people say. One former Amazon worker says she had flexibility to work from home and other Amazon mothers who didn't would bring their children to her house on snow days or when teachers went on strike, making her place a de facto day care center.

Liz Swanby, a seven-year Amazon employee who oversees shipping hubs in the Midwest, says the company has supported her through two pregnancies, including one with complications. Amazon helped her plan in advance how to use the benefits and adjusted them as needed.

“My mind was not on work whatsoever and it was super helpful,” says Swanby, whose wife stays home with the couple's son, 3, and daughter, 2. “Amazon does a lot to support families.”

Despite Amazon's reputation for frugality, it will occasionally dig deep to project an image of a hip, forward-thinking company. The new Seattle headquarters has rooftop dog parks and a tree house inside plant-filled spheres where employees can wax creative. The moms group says it's time for the company to keep up with the rest of the tech industry by giving working parents the flexibility and support they need to balance professional and family demands. Some moms say backup day care would be especially beneficial for households with two parents working outside the home.

“The childcare topic was quickly identified as one of our biggest priorities,” states an email that circulated recently among the Momazonians. “We assert that a key to increasing diversity of women is to prioritize parent-friendly benefits and policies.”

— With assistance by Dina Bass, Mark Gurman, Gerrit De Vynck, and Sarah Frier

Read more: 

• 2018: The year of Amazon
• Parental biases are different for single moms and dads
• Microsoft, fighting class action, acknowledges gender imbalances in tech industry

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