The Pregnant Workers Fairness Act (PWFA) is being hailed as the biggest win for pregnant workers’ rights in more than 40 years, Axios reports. While women have sued their employers in the past based on the 1978 Pregnancy Discrimination Act, they would often lose since that law did not explicitly cover accommodations. The PWFA became effective June 27 and mandates employers with more than 15 employees give their pregnant workers reasonable accommodations in the workplace.

“It also gives employees a right to request and receive accommodation from childbirth and pre- and post-partum conditions related to pregnancy like infertility, abortion, and lactation,” the ACLU and the Center for WorkLife Law noted in a joint report.

“Modeled on the Americans with Disabilities Act, employers must grant pregnant workers an accommodation so long as it is ‘reasonable’ and does not impose an ‘undue hardship' on the employer,” the ACLU says. “Such clarity will aid workers and their employers alike in reaching mutually-agreeable solutions, with less cost and disruption—not to mention delay—than litigation.”

President Joe Biden endorsed the bipartisan provision within a $1.7 trillion budget bill that he signed two days before Christmas last year. In the lead up to the signing of that bill, the National Partnership for Women and Families advocated for its passage, noting in a report that nearly 2.8 million pregnant women each year, or 70% of all pregnant women, were working while they were pregnant.

Despite the widespread praise for the new law, Kathleen Gerson, a professor of sociology at New York University who has specialized on gender and employment, says it is still too early to know how impactful it will be, NBC News reports. The PWFA doesn’t guarantee paid parental leave, a necessary protection for workers after they give birth, Gerson said. She also is waiting to see what the Equal Employment Opportunity Commission deems is “reasonable accommodations” under the law.

“Certainly it’s good news—there’s no question about that,” Gerson said. “The question really is, how good is the news and how much more will be left to be done?”

The EEOC has been collecting complaints of alleged violations happening on or before June 27, Melissa Losch, of counsel at law firm McGlinchey Stafford, writes for JD Supra. While the PWFA specifically requires accommodations for “known limitations” connected to pregnancy and childbirth, it’s still not clear what the definition of these limitations are, Losch notes.

“Pregnancy, in and of itself, is not a ‘limitation’ requiring an accommodation, and the PWFA does not specify which conditions may constitute ‘known limitations,’” Losch writes. “Until regulations are adopted to provide more guidance, employers should use extreme caution and obtain fact-specific legal advice before questioning any non-obvious limitations communicated by an employee.”