Microsoft co-founder and philanthropist Bill Gates fears President Trump’s “global gag rule,” a policy that blocks funds to organizations that offer abortion advice and care in foreign countries, may endanger millions of woman and children. Gates, alongside his wife and co-chair Melinda, voiced criticism of the rule in an interview published today in The Guardian.

The two philanthropists oversee the Bill & Melinda Gates Foundation, the world’s largest and most charitable private foundation. The duo fear their work will be undercut by the gag rule, while its poor implementation could result in a significant loss of life. “We’re concerned that this shift could impact millions of women and girls around the world,” Melinda Gates says. “It’s likely to have a negative effect on a broad range of health programs that provide lifesaving treatment and prevention options to those most in need.”

The gag rule, first put in place by Ronald Reagan and reinstated last month through an executive order shortly after Trump took office, is designed to put pressure on foreign nonprofits to shy away from any and all abortion-related activities. This includes not just providing abortions, but also providing any information about abortions whatsoever. Trump’s order was also overly broad, encompassing any overseas organization that receives US aid and not simply those in the family planning sector.

“This includes programs that prevent and treat HIV, TB and malaria, and provide healthcare to women and children around the world,” Melinda Gates says. “Enabling women to time and space their pregnancies and providing access to treatment and prevention of infectious diseases is lifesaving work. It saves moms’ lives and it saves babies’ lives, and that has long had wide support in the United States.”

Bill Gates is concerned that he and Melinda’s foundation, though flush with tens of billions of dollars, is still not capable of making up for the loss of funds. “The US is the No. 1 donor in the work that we do,” Bill Gates says. “Government aid can’t be replaced by philanthropy. When government leaves an area like that, it can’t be offset, there isn’t a real alternative. This expansion of this policy, depending on how it’s implemented, could create a void that even a foundation like ours can’t fill.”