The suit was filed in federal court in Michigan on Friday on behalf of a woman who says she did not receive accurate information or care at a Catholic hospital there, exposing her to dangerous infections after her water broke at 18 weeks of pregnancy.
In an unusual step, she is not suing the hospital, Mercy Health Partners in Muskegon, but rather the United States Conference of Catholic Bishops.
Its ethical and religious directives, the suit alleges, require Catholic hospitals to avoid abortion or referrals, “even when doing so places a woman’s health or life at risk.”
The suit opens a new front in the clash over religious rights and medical care. The Catholic Church has fought against requiring all health plans to include coverage of contraception and is likely to call the new lawsuit an attack on its core religious principles.
Catholic hospitals account for about one in six of the country’s hospital beds and in many regions their influence is spreading as they forge alliances with non-Catholic medical groups.
“This isn’t about religious freedom, it’s about medical care,” said Louise Melling, deputy legal director of the civil liberties union, in a telephone news conference on Monday.
Both the Muskegon hospital and the bishops conference declined to comment.
Tamesha Means, the plaintiff in the lawsuit, said that when she was 18 weeks pregnant her water broke and she rushed to Mercy Health, the only hospital in her county.
Her fetus had virtually no chance of surviving, according to medical experts who reviewed the case, and in these circumstances doctors usually induce labor or surgically remove the fetus to reduce the mother’s chances of infection.
But the doctors at Mercy Health, Ms. Means said, did not tell her that the fetus could not survive or that continuing her pregnancy was risky and did not admit her for observation.
She returned the next morning, bleeding and in pain, and was sent home again.
That night she went a third time, feverish and writhing with pain; she miscarried at the hospital and the fetus died soon after.
At the news conference Monday, Dr. Douglas W. Laube, an obstetrician at the University of Wisconsin Medical School, described the care Ms. Means received as “basic neglect.” He added, “It could have turned into a disaster, with both baby and mother dying.”
The A.C.L.U. said it had filed suit against the bishops because there had been several cases in recent years in which Catholic hospital policies on abortion had interfered with medical care.
John M. Haas, president of the National Catholic Bioethics Center in Philadelphia and an adviser to the bishops, said he could not speak about the current suit because he was unfamiliar with it.
But he said that the bishops’ directives were more nuanced than critics allege, allowing for actions to treat a woman at risk even if that treatment might result in the loss of the fetus.
He said some hospitals might have misinterpreted the bishops’ rules and added that doctors were required to tell patients of potential risks and alternatives, though they may not provide direct abortion referrals.
In 2010, the diocese of Phoenix stripped a hospital of its affiliation after doctors there said they performed an abortion to save a mother’s life.