The United States is ending its financial support for family planning programs in developing countries, cutting nearly 50 million women off from access to contraception.

This policy change has attracted little attention amid the wholesale dismantling of American foreign aid, but it stands to have enormous implications, including more maternal deaths and an overall increase in poverty. It derails an effort that had brought long-acting contraceptives to women in some of the poorest and most isolated parts of the world in recent years.

The United States provided about 40 percent of the funding governments contributed to family planning programs in 31 developing countries, some $600 million, in 2023, the last year for which data is available, according to KFF, a health research organization.

That American funding provided contraceptive devices and the medical services to deliver them to more than 47 million women and couples, which is estimated to have averted 17.1 million unintended pregnancies and 5.2 million unsafe abortions, according to an analysis by the Guttmacher Institute, a sexual health research organization. Without this annual contribution, 34,000 women could die from preventable maternal deaths each year, the Guttmacher calculation concluded.

“The magnitude of the impact is mind-boggling,” said Marie Ba, who leads the coordination team for the Ouagadougou Partnership, an initiative to accelerate investments and access to family planning in nine West African countries.

The funding has been terminated as part of the Trump administration’s disassembling of the United States Agency for International Development. The State Department, into which the skeletal remains of U.S.A.I.D. was absorbed on Friday, did not reply to a request for comment on the decision to stop funding family planning. Secretary of State Marco Rubio has described the terminated aid projects as wasteful and not aligned with American strategic interest.