In 2009, Mindy Swank was 20 weeks into a difficult pregnancy when her water broke. Her doctors said the baby, already suffering from severe anomalies, would not survive, and they recommended she terminate the pregnancy immediately to avoid the risk of infection. Yet for nearly two months, Swank’s hospital in Silvis, Illinois, refused to perform the procedure. It wasn’t until Swank woke up one morning bleeding profusely that the hospital finally agreed to induce labor.

“I brought all the pads I had soaked through, and all the underwear,” Swank recalls. “I shoved it in a nurse’s face, and I said, ‘Is this enough blood for you?’ And I kid you not, they measured the blood. I had to be hemorrhaging before their rules would let them do this.”

Swank was shocked that the hospital, Genesis Medical Center, had stood in the way of a procedure her doctors had advised. “I thought when something like that happens, it’s a medical issue and the doctors are there to help you,” she says. But her doctors, it turned out, were not the ultimate authority at Genesis. “In agreement with Catholic doctrine,” the hospital informed Swank, “we must consider only grave and imminent threat to maternal health.”

In recent years, Catholic hospitals across the country have come under fire for denying reproductive care to their female patients. But the fact that Genesis adheres to Catholic restrictions came as a surprise to Swank, for a simple reason: The hospital isn’t run by the Catholic church. Its web site, in fact, makes no reference to Catholic doctrine, boasting instead that the hospital “has a tradition that always puts the patient first.”

Genesis—which operates more than 100 health care facilities in Illinois and Iowa—is part of a growing trend known as “zombie religious hospitals,” a term coined by Elizabeth Sepper, a law professor at Washington University who has studied the trend. As more and more hospitals merge, Catholic providers are imposing their religious restrictions on patients at secular facilities. Since 2001, the number of acute care hospitals operating under Catholic doctrine has shot up 22 percent. “It’s the spread of religious restrictions and identity beyond the bounds of places we think of as religious,” Sepper says. Today, one in every six hospital beds nationwide are subject to Catholic restrictions, which prohibit doctors from prescribing birth control pills, implanting IUDs, distributing condoms, administering fertility treatments, or performing sterilizations.

As Mindy Swank discovered, it’s often impossible to know when a secular hospital is operating under Catholic restrictions. Genesis became a zombie religious hospital in 1994, during a merger with Catholic Mercy Hospital in Davenport, Iowa. The trend has accelerated in recent years, as secular hospitals have joined forces with Catholic facilities in an effort to hold their own against insurance companies and to comply with requirements for greater collaboration under the Affordable Care Act. In five states—Alaska, Iowa, South Dakota, Washington, and Wisconsin—more than 40 percent of acute care hospital beds now fall under Catholic doctrine.

As the dominant players in the industry, Catholic hospitals are often able to force secular facilities to adopt religious restrictions during negotiations over mergers or partnership deals. In 2011, when Catholic Providence Health & Services became affiliated with Swedish Medical Center in Seattle, the secular hospital assured concerned patients that nothing would change. “Swedish will still be Swedish,” the hospital vowed. “We are keeping our name and will not become a Catholic organization.” But after the deal was signed, Swedish stopped providing elective abortions, in keeping with Catholic doctrine.

The following year, Jewish Hospital and St. Mary’s Healthcare in Louisville, Kentucky, merged with St. Joseph Health System in Lexington to form KentuckyOne Health, the largest health care system in the state. Operated by Catholic Health Initiatives, a nonprofit based in Colorado, KentuckyOne re­quires all of its facilities—including Jewish Hospital—to abide by Catholic directives.

By accepting religious restrictions, critics say, secular hospitals are putting business considerations ahead of patient care. Lois Uttley, who tracks hospital deals as the director of MergerWatch, calls the spread of zombie hospitals a “creeping threat.” Catholic directives, she says, are often treated as an afterthought during merger negotiations. But over time, she warns, “pressure grows to make the hospital follow all the Catholic restrictions.”

Indeed, secular hospitals often fail to recognize how acceding to religious rules will undercut the relationship between doctors and patients. “They agree to do it in the interest of getting the sale through, without realizing that it will tie their doctors’ hands and limit the services their patients can get,” says Dr. Debra Stulberg, an assistant professor of family medicine at the University of Chicago.

As more and more hospitals adopt religious rules, millions of Americans—regardless of their faith—are being denied access to critical services. Some zombie systems, like Genesis, refer patients to alternative facilities when their ethics guidelines don’t allow a given procedure. Some doctors can also find ways to quietly break the rules when necessary. But as mergers increase, access to alternative health care providers has dwindled. And requiring doctors to sneak around in order to care for their patients properly is hardly a satisfying solution for anyone involved.

“Is this how medicine should be practiced—with doctors making up funny work-arounds with weird charting?” asks Lori Freedman, a University of California sociologist who studies zombie religious hospitals. “It wouldn’t be tolerable in any other aspect of medicine.”

The public, unfortunately, has little recourse when their local hospital merges with a Catholic facility. Only six states require a public hearing on proposed hospital mergers, and only nine states require that consumers be represented on the reviewing bodies that must approve the deals. Even then, the public may not fully comprehend the impact of such mergers. “Most of these communities are just relieved that their hospitals are going to stay open,” says Lisa Ikemoto, who teaches public health law at the University of California–Davis. “They don’t think about the terms under which that’s going to happen.”

Those terms, as Mindy Swank learned, can place women in a life-or-death situation. Swank, who grew up identifying as pro-life, says her ordeal at Genesis made her a firm believer in a woman’s right to choose. “I did not understand why my local secular hospital could not provide an abortion, especially when they knew the baby wasn’t going to live,” she says. “Whose life is being saved here?”