For decades, religious authorities have helped determine what kinds of care can be offered in Catholic institutions, based on theological concepts like the sanctity of human life. But what was permitted and forbidden wasn’t always clear to the nuns running the hospitals, according to Barbra Mann Wall, a historian at the University of Virginia who has studied the evolution of Catholic health care in the U.S. As a result, doctors sometimes had more opportunities to seek exceptions for patients or offer care through loopholes in the system in the past than they do today. Now, the nuns’ role has faded and Catholic bishops preside over hospitals that tend to be part of massive health care networks, where part of their role is to hold the line against procedures the church has forbidden. And they often use a stricter interpretation of religious doctrine — with fewer exemptions for patients — than the nuns once did.

Amid those shifts, the number of hospitals following Catholic doctrine has grown all over the country, not just in rural areas. Best estimates suggest that one in six hospital beds and many of the nation’s largest nonprofit health systems are Catholic-owned or -affiliated. From 2001 to 2016, the number of Catholic-affiliated hospitals in the U.S. grew by 22 percent, even as the total number of hospitals in the U.S. shrunk, according to research by MergerWatch and the American Civil Liberties Union. And the changes vary by region. In Washington state, more than 40 percent of hospital beds are in Catholic institutions. In several Midwestern states, more than 30 percent of beds are in Catholic hospitals.