Beyond new state efforts to restrict women’s access to proper reproductive health care, another, if quieter, threat is posed by mergers between secular hospitals and Catholic hospitals operating under religious directives from the nation’s Roman Catholic bishops. These directives, which oppose abortions, inevitably collide with a hospital’s duty to provide care to pregnant women in medical distress. This tension lies at the heart of a federal lawsuit filed last week by the American Civil Liberties Union.

The suit was brought on behalf of a Michigan woman, Tamesha Means, who says she was subjected to substandard care at a Catholic hospital — the only hospital in her county — after her water broke at 18 weeks of pregnancy. Doctors in such circumstances typically induce labor or surgically remove the fetus to reduce the woman’s chances of infection. But according to the complaint, doctors acting in accordance with the bishops’ directives did not inform Ms. Means that her fetus had virtually no chance of surviving or that terminating her pregnancy was the safest treatment option.

Despite acute pain and bleeding, Ms. Means was sent home twice, and when she returned a third time with a fever from her untreated infection, she miscarried even as the paperwork was being prepared to discharge her again. The fetus died soon after.

The case has gained attention because Ms. Means is not suing the hospital for medical negligence but the United States Conference of Catholic Bishops. The A.C.L.U. is arguing, on her behalf, that having issued the mandates and made them conditions of hospital affiliation, the conference is responsible for “the unnecessary trauma and harm” that Ms. Means and “other pregnant women in similar situations have experienced at Catholic-sponsored hospitals.”