It was painful to hear but ultimately seemed the best course to Jessica Mann and her family. Because of a dangerous tumor in her brain, her doctor gently suggested that she take steps to make sure that she could not get pregnant again.

So Mann, 33, who is due to have her third baby next month, decided that while she was under anesthesia during the birth, she would undergo a tubal ligation – a procedure that would prevent further pregnancies.

But her hospital said no. Genesys Regional Medical Center, which is Catholic, denied the request on religious grounds: Catholic mandates forbid procedures that cause sterilization, including vasectomies, and officials said she did not qualify for an exception.

“I was surprised and upset,” said Mann, who on Friday sent a letter through the American Civil Liberties Union threatening legal action. “And there was anger at the fact that they can disregard medical issues for their religious beliefs.”

Mann’s situation is the latest to draw attention to the simmering debate over religious liberties and how far people and organizations of faith may go in denying people services that conflict with their beliefs.

That battle flared earlier this month in Kentucky, where a county clerk who opposes same-sex marriage because of her Apostolic Christian faith refused to issue marriage licenses to gay couples. And it has raged in court, as organizations have resisted an Obama administration mandate that most employers cover contraceptives as part of their company health insurance plans.

A less noisy fight has involved Catholic hospitals, which have taken a larger share of the hospital market in recent years. Neither Genesys Regional Medical Center nor Ascension, the nation’s largest Catholic and nonprofit health system, of which Genesys is a member, responded to requests for comment.

Federal law provides an “iron-clad” exemption for medical providers who do not want to provide abortion or sterilization services, said Robin Wilson, a law professor at the University of Illinois. More-limited protections exist for providers with other faith-based limitations, although many states require them to provide necessary care to a person in an emergency.

The U.S. Conference of Catholic Bishops has issued a set of ethical and religious directives for Catholic hospitals that bar the institutions from promoting contraceptives, providing abortions, or doing procedures with no other intention but to sterilize the patient, such as a vasectomy.

Catholic hospitals vary in terms of how strictly they adhere to the bishops’ guidelines, but critics say the rules are applied to a growing number of patients because of the proliferation of Catholic-affiliated institutions.

According to a 2013 report from the ACLU and MergerWatch, another group scrutinizing Catholic hospitals, the number of Catholic acute-care nonprofit hospitals increased 16 percent between 2001 and 2011 even as the total number of hospitals declined.

By 2011, the report found, 10 percent of all acute-care hospitals were Catholic-sponsored or -affiliated, representing about 1 in 9 hospital beds in the country.

Officials with the ACLU argue that the federal protections cited by Wilson do not apply in the Mann case. And they say that the guidelines not only substitute religious doctrine for best medical practices but disproportionately harm women because of the focus on reproductive issues.

“These ethical and religious directives single out women and care that women need,” said Brigitte Amiri, a staff attorney with the ACLU.

So far, however, that argument has gotten little traction in court. This year, a federal judge sided against a different Michigan woman who said she was denied critical care because of the guidelines. The ACLU is appealing the decision, which was made on jurisdictional grounds.

The woman in that case, Tamesha Means, had been receiving prenatal care from a doctor affiliated with a Catholic hospital when her water broke at 18 weeks. In a lawsuit filed against the bishops’ group, Means argues that the hospital failed to discuss with her the possibility of terminating her pregnancy and instead gave her false hope that the fetus could be saved. Ultimately, she contracted an infection and miscarried.

Wilson said judges must tread especially carefully in situations such as Mann’s, which are not acute emergencies.

“If it’s not an emergency, why should you wash out the religious character of that hospital?” she said. “You want a diversity of providers so people who have different values can actually find providers who match those values.”

Mann says it’s not that simple.

The Flushing, Michigan, social worker was diagnosed a decade ago with two pilocytic astrocytomas, benign brain tumors that can cause blindness or paralysis, among other problems. She underwent emergency surgery to get one removed and has been getting regular care and monitoring to ensure that the other tumor remains harmless, she said.

When she became pregnant three years ago, hers was treated as a high-risk pregnancy. The tumor required that she deliver via Caesarean section while fully anesthetized, rather than under partial anesthesia that numbs the lower body, which is more common.

When she became pregnant with her third child, a girl, she and her husband were elated, she said. But a maternal-fetal-medicine specialist told them earlier this spring that Mann should undergo tubal ligation to ensure that this would be her last child.

“You know, it’s never easy to hear that. But I have accepted it,” said Mann, who has two other children. “I talked it over with my husband. We want me to be around. That’s the biggest thing.”

Mann had heard that Genesys had changed their policies last year and that the tubal ligation would have to be specially requested. Indeed, an Oct. 1, 2014, memo to staff, provided to The Washington Post by the ACLU, said the hospital would halt all planned sterilizations to “strengthen our alignment with the Catholic Ethical and Religious Directives.”

The hospital had indicated it would make some exceptions to the policy for medical reasons, so Mann requested one in May. But early this month, her doctor informed her that the hospital had said no.

The family is in the process of finding a new hospital and doctor while the ACLU presses their case. Being forced to change physicians and hospitals at this late stage in the pregnancy is frustrating and stressful, she said.

Hospital administrators have suggested that she go through with the birth at Genesys and then get the tubal ligation at a later date at a different hospital. But another surgery weeks after a Caesarean could be just as harmful to her health as another pregnancy, her doctor has said.

“The feeling of the unknown is stressful and disheartening,” said Mann, whose mother and grandmother were staunch Catholics and who herself identifies as a Christian. “But I have the support of my husband and my doctor, so I can’t let it affect me too much.”