Imagine you’re an OB/GYN doing a C-section on a woman who’s had six previous C-sections. She says she’s done having kids and has asked to have her tubes tied at the same time as the C-section, which is standard procedure. But if you work at a Catholic hospital, you can’t do it—they officially prohibit sterilization.

“I’m thinking, you know, if I tie her tubes I’m going to get kicked off the staff. And I just don’t think that’s right,” said a doctor who faced just such a scenario.

And she isn’t alone in her frustration. According to a first-of-its-kind study, OB/GYNs across the country are concerned that the Catholic ban on tubal ligations (the clinical term for “tying tubes”) poses a “risk of harm” to women by violating the accepted standard of care, especially for women who are already getting a C-section and would need an unnecessary second surgery. “[If] someone who’s had four C-sections before has to have another operation to get her tubes tied, that’s not what’s in her best interest by any stretch of the imagination,” said another doctor in the study.

Thanks to the battle over contraception coverage in the Affordable Care Act, it isn’t news that many Catholic institutions do not provide contraceptives. But less attention has been paid to the fact that Catholic hospitals already have a “conscience exemption” under federal law from providing contraceptive sterilization, which is the second most common form of birth control in the United States. And despite the availability of sterilization procedures at outpatient surgical centers, in-hospital tubal ligation remains such a popular procedure that one in 10 childbirths ends with one.

As a follow-up to a 2012 study that found that half of all OB/GYNs working at Catholic hospitals had conflicts with their hospital over religiously based policies for patient care, Dr. Debra Stulberg of the University of Chicago, medical sociologist Lori Freedman of the University of California, San Francisco, and colleagues conducted in-depth interviews with a sub-sample of physicians to pinpoint the specific conflicts.

They weren’t surprised when doctors mentioned restrictions on abortion. There have been several high-profile cases where doctors clashed with Catholic hospital administrators over abortions for women who were experiencing catastrophic miscarriage or had a life-threatening health condition. But these cases are relatively rare. What was surprising, Freedman says, was how often doctors mentioned the denial of medically indicated sterilization. “What was striking was that it was the most common thing that bothered people in a daily way,” she says. “Doctors were really dying to talk about this because it’s kind of freaking them out.”

Catholic hospitals are prohibited from providing sterilization under the Ethical and Religious Directives for Catholic Health Care Services, which are issued by the U.S. Conference of Catholic Bishops and enforced by local bishops. But some Catholic hospitals quietly provided them if they were medically indicated, especially if a woman was already having a C-section and faced a health risk from another pregnancy.

In the early 2000s, however, the Vatican began insisting on stricter enforcement of the directives, which was right around the time the Catholic health system began growing due to a series of mergers—the number of Catholic hospitals increased 16 percent between 2001 and 2011. The study found several examples of tightening enforcement of the sterilization ban because of a more conservative bishop or new hospital management. “The bishop in [my city] was fairly liberal,” said one doctor who noted that his hospital used to perform tubal ligations for women who were at risk of gestational diabetes. “But then the bishop became much more conservative and the diocese became much more conservative and it’s absolutely never allowed.”

“Many doctors we spoke to had been given assurances when they were hired or when the hospital changed ownership that there would be ways of allowing tubal ligations if it was medically in the women’s best interest. That was not the case,” Stulberg says.

In early December, the ACLU filed a complaint with the Michigan Department of Licensing and Regulatory Affairs after Genesys Health System, a Catholic hospital in Grand Blanc, changed its policy to implement a total ban on tubals. The ACLU received a complaint from a woman identified as “Mrs. B” whose tubal was cancelled less than two weeks before her scheduled C-section. She had to forgo the procedure because her doctor only had admitting privileges at Genesys. The ACLU called the policy “contrary to the appropriate standard of care.”

“Everything we do in medicine is about risk and benefits,” Stulberg says, “and when you have a treatment that is all benefit and no risk, it feels crazy not to provide it.” And while outpatient procedures like Essure, a non-surgical sterilization method that blocks the fallopian tubes with inserts, are available, she notes there are indications that they're not as effective as traditional sterilization. And because Essure takes a minimum of nearly five months post-partum to become effective, it still places women at some risk for unplanned pregnancy after getting the procedure.

The Catholic Health Association, which represents the U.S.’s 642 Catholic hospitals, declined to comment on the study. It argues that it’s a matter of protecting the consciences of Catholic hospitals to allow them to refuse to provide sterilizations, since Catholic doctrine considers sterilization nearly as egregious as abortion. Forcing hospitals to provide them would challenge “the fundamental values of Catholic healthcare,” according to a statement by the CHA. The organization also disputes the idea that women’s health services like tubal ligations are basic healthcare that should be provided at all hospitals.

As with access to other reproductive health services, it’s lower-income women who feel the restrictions most acutely. Women of color and those who don’t have a college education are more likely to rely on contraceptive sterilization for birth control. And women who are on Medicaid or live in rural areas often have only one hospital they can go to—one-third of Catholic hospitals are rural community hospitals. “Our hospital is the main maternity hospital and our patients … tend to be of the lower socioeconomic status,” said one doctor. “If you had insurance …  you could go across the street and get your tubal done. But if you were getting Medicaid … then you didn’t have access to that.”

For many women, the result is an unplanned pregnancy. One study of largely low-income women who were denied sterilizations for non-religious reasons at a university hospital in Texas found nearly half had a repeat pregnancy within a year.

But with private insurance plans increasingly restricting patients’ choice of hospitals and with one in six patients in the U.S. receiving care at Catholic hospitals, more women are at risk of running afoul of Catholic health restrictions. “Women say, ‘this isn’t my religion, why does this apply to me?’” Stulberg says “The church and the hospital say this is elective [or nonessential], but women don’t always have choices.”