When Latavia Johnson discovered she was expecting, she didn’t know she was in for an unpleasant surprise at work. Newly hired at a Granite City, Illinois, Walmart, she tried to follow medical advice and ask her managers for a job that didn’t involve heavy lifting—it seemed a simple enough request, since her job was decorating cakes.

But instead of getting light duty, she recalls, she got less work. The management decided that rather than accommodating her with an adjusted workload, Walmart would simply stop giving her shifts. Yet they kept her on the on-call schedule, so she sometimes reported to work as ordered, only to be told by her supervisor, “If I see you here, I’m going to send you home.”

But Johnson didn’t need bed rest, she needed hours, and even after she pushed to be allowed back to work, her schedule was severely reduced. “I just wanted to work and be able to support myself, but I didn’t want to injure myself working,” she recalls. “I didn’t want to lose my baby working.”

This week, the Supreme Court got Johnson’s back. They ruled 6-3 in favor of Peggy Young, a UPS worker who was instead forced onto unpaid leave when she was pregnant. Young, at the time, said she was willing and able to keep working as a letter carrier. But despite UPS’s willingness to make adjustments for male co-workers with disabilities, she was pushed off the job because she was advised to avoid lifting parcels heavier than twenty pounds.

The Supreme Court decided Young should have been able to keep working for UPS and the company was required by law to accommodate her, clarifying the protections of the 1978 Pregnancy Discrimination Act. That law sought to expand sex discrimination protections by mandating that employers accommodate pregnant workers in a way that was comparable to other workers with similar impairments. Under a narrow reading of the law, the process of proving discrimination “on the basis of pregnancy, childbirth, or related medical conditions” requires the worker to show that a non-pregnant worker who faced a “similar” disability would receive more favorable accommodation. This business-friendly reading currently gives employers room to wriggle out of the mandate by contending that pregnancy is a special category of impairment, and thus isn’t exactly comparable to other temporary disabilities that employers cover under disability policies.

But activists have long criticized this interpretation for placing the burden of proof on the worker to show that her circumstances are technically analogous to the needs of a non-pregnant co-worker “similar in their ability or inability to work.” In contrast, under the more stringent Americans with Disabilities Act (ADA), to be exempt from “reasonable accommodation” standards, an employer must demonstrate that the accommodation would cause “undue hardship” for the business.

The Supreme Court ruled that if a workplace was already accommodating other, basically analogous forms of disability, it was up to the employer to justify the refusal to accommodate a pregnant woman—rather than force the pregnant woman to prove she deserved equal treatment. So a pregnant worker should be able to demand a reasonable accommodation at work, like being able to sit on a stool instead of standing at a counter all day. The ethical logic here is a feminist concept: a woman shouldn’t have to prove to her boss why she deserves the same rights at work as a male coworker.

Pregnancy discrimination is an issue not just of labor rights but of reproductive justice, since the kind of flexibility that pregnant workers require is often denied to women in more low-paying, physically demanding work, which, according to a National Women’s Law Center’s analysis, disproportionately affects low-income women, “women of color and immigrant women.” Since the majority of women entering the workforce are projected to be pregnant on the job at some point, employers who ignore all their needs are both eroding the principle of gender equality and foreclosing the economic potential of a huge swath of the population.

Several states, including California and Illinois, have already enacted additional anti-discrimination protections for pregnant workers, folding into a broader push to strengthen safeguards for workers in precarious jobs, who are burdened by a combination of low wages, unstable schedules and no paid leave time.

Recognizing that pregnancy requires both the right to workplace accommodation and the right to negotiate for fair working conditions, the Equal Employment Opportunity Commission (EEOC) recently affirmed that pregnant workers were generally entitled to accommodations comparable to those offered to workers with temporary disabilities.

Advocates are now urging Congress to pass the Pregnant Workers Fairness Act, which would bring the 1978 protections into line with the standards of the ADA. A clear nationwide standard, according to Vicki Shabo of the National Partnership for Women and Families, would protect all women at work, “eliminating the need for workers to go to court to determine whether an employer must provide accommodations for pregnancy,” thus ensuring their rights at work aren’t dependent on an employer’s whim. UPS and Walmart, for example, have reformed their pregnancy policies, but only after facing legal and political pressure—though Walmart insists its pregnancy policy well exceeds federal standards.

Today, labor advocates say pregnancy regularly forces women to either needlessly stop working or expose themselves to unnecessary workplace risks: they might be fired just for asking for a water bottle at work or extra bathroom breaks, for example—even when their male coworker gets light duty when he pulls a muscle.

Betzaida Cruz Cardona recently complained to the EEOC about being deemed unfit for work because her doctor advised her not to lift more than twenty-five pounds during her pregnancy. Her boss decided to let her “stay home and take care of my pregnancy,” by forcing her off the job, which left her penniless and homeless. Similarly, Walmart worker Candis Riggins complained to the EEOC that her supervisors ignored her pleas to switch to job duties that didn’t expose her to hazardous cleaning chemicals, until one day she collapsed.

The struggle continues after pregnancy too, as unstable low-wage jobs often end up costing families more than they pay. Like many Walmart part-timers, Latavia says she’s ready to return to work after childbirth, but can’t afford childcare. “If I went back to work,” she explains, “I would actually be paying the babysitter what I’m going to basically make at Walmart.”

While these hardships weigh on workers at any stage in life, pregnancy is the most vulnerable, and pivotal, point in a woman’s life. Whatever injustice she suffers when she’s expecting will hurt the next generation before it even begins.