The mayor, Elpidia Saavedra, 47, had an obstetric emergency 10 years ago when an ectopic pregnancy ruptured. Semone Dittentholer, 39, said she almost died as a teenager, when she miscarried and lost massive amounts of blood.

“It’s a lifeline that we’ve had, and now that part of that lifeline is getting cut down,” said Ms. Dittentholer, who works on the reservation at the Ttawaxt Birth Justice Center, which offers support to pregnant women and to new mothers and has been providing space for a local obstetrician to see women once a week in order to ease access to care.

“It’s just another reminder of how scary it can be out here.”

The United States is already the most dangerous developed country in the world for women to give birth, with a maternal mortality rate of 23.8 per 100,000 live births — or more than one death for every 5,000 live deliveries.

Recent figures show that the problems are particularly acute in minority communities and especially among Native American women, whose risk of dying of pregnancy-related complications is three times as high as that of white women. Their babies are almost twice as likely to die during the first year of life as white babies.

Women of color are more likely to live in maternity care deserts or in communities with limited access to care. According to the March of Dimes, the maternal health nonprofit, seven million women of childbearing age reside in counties where there is no hospital-based obstetric care, no birthing center, no obstetrician-gynecologist and no certified nurse midwife, or where access to those services is limited.

Fewer than half of women in rural areas can find perinatal care within 30 miles, according to the Centers for Medicare and Medicaid Services.

The closure of an obstetrics unit often begins a downward health spiral in remote communities. Without ready access to obstetricians, prenatal care and critical postpartum checkups, risky complications become more likely.