“There's not a forgiving culture for new moms in the workplace,” says Alexis Diao, a producer at NPR with two young kids. “There is intense pressure to prove that you're the same woman before childbirth and before pregnancy.”

Motherhood is one of the biggest causes of the gender pay gap. Women's earnings drop significantly after childbirth, while men's don't. That divergence starts the day new moms get back to the office, especially for those who choose to breastfeed. “There's a real incompatibility in the U.S. with breastfeeding and continuing to work full-time,” said Phyllis Rippey, a sociologist at the University of Ottawa who has studied breastfeeding and women's earnings.

Not all moms choose to or are physically able to breastfeed; for those who do, the American Academy of Pediatrics recommends that infants be breastfed during the first year for the best health outcomes. Since only 15 percent of U.S. workers get any paid time off to care for newborns, most working moms are forced to pump at work to keep up with those recommendations.

It's hard to measure exactly how much breastfeeding hurts women's long-term earnings, because few surveys look at the two together, said Rippey. In a 2012 study, Rippey looked at a rare data set that quantified both issues for mothers with children born from 1980 to 1993. They found that women who breastfed for at least six months suffered more severe and prolonged earnings losses than mothers who breastfed for less time or not at all.

“I call it a breast-feeding penalty,” Rippey said.

Women face stigma for taking time away from their jobs, and they run up against the reality that the workday doesn't stop when they leave to go pump. Breast pumping requires a strict schedule that doesn't fit squarely in the traditional workday. Pumping times can vary anywhere from 15 minutes to an hour. Women have to pump multiple times during the workday. That doesn't mesh with the workday.

“Having to step away and pump when you're at the office can be an isolating experience. You are essentially locking yourself in a room and, in your deepest insecurities, confirming to people that despite your best efforts, you have changed,” Diao said. (NPR, where she works, has on-site lactation rooms.)

Diann Burns, a Virginia based attorney with three kids, said that a former employer said her productivity lagged when she started breast pumping—just before laying her off. “There is an 'I'm-doing-less-work-attitude' about it, in spite of the fact that I'm not taking a smoke break like other employees,” she said. “No employee works every minute. I know I have to get my work done and then pump around it.”

Workplaces have improved conditions for breastfeeding moms in the past 30 years. A 2010 amendment to the federal Fair Labor Standards Act requires employers to provide reasonable break time and a place other than a bathroom for women to pump for as much as one year after the birth of the child. Twenty-nine states also have laws related to breastfeeding in the workplace. Around half of employers have on-site lactation rooms, up from 28 percent in 2014, according to a 2018 survey of over 3,000 employers from the Society for Human Resource Management.

Still, many women don't have workplaces with such accommodations. Only about 40 percent of women have access to a private space, other than a bathroom, to pump, a 2016 study from the University of Minnesota found. The schools at which Chelsea Wilson works as a nurse, for example, don't have dedicated lactation rooms. She has pumped in bathrooms, supply closets, and in other people's offices.

“There is still a large problem with compliance,” said Galen Sherwin, a lawyer at the ACLU. “There's this notion that women are seeking 'special' accommodations, as opposed to seeking conditions that make it possible for them to return to work when they have babies.”

Rippey found that women's earnings took a big hit because many of them left the workplace altogether. But women are more likely to quit breastfeeding than quit their jobs entirely. The harder that workplaces make it for moms to pump, the less likely they'll stick with it, the University of Minnesota study also found. Women who had accommodations were 2.3 times more likely to continue exclusively breastfeeding at the six-month point, the researchers found. “A lot of women feel stressed,” said Pat McGovern, one of the researchers on the study. “If they're racing to this space to breastfeed and back to their office, and don't feel their direct supervisor is supportive, it can be very stressful.”

Chavi Lieber, a journalist who works at Vox Media, stopped breastfeeding her newborn at six months because “the lifestyle of the job really isn't cut out for it,” she said. Her office has a mother's room, but she spends a lot of her time elsewhere. Once, when she found herself in midtown Manhattan without a place to pump, she ducked into the bathroom at Tiffany & Co. “While society as a whole loves to pressure women into breastfeeding, it sure wasn't ready to accommodate a pumping business reporter when I actually needed the physical space to do it.”

Read more:

• Many employees still can't find a spot to breast-feed
• How employers can help new moms transition back to work
• Parental biases are different for single moms and dads

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