The American Civil Liberties Union and George Washington University Medical Center, antagonists in a three-year legal battle of mother against fetus, settled it yesterday with the nation's first agreement guarding pregnant women's rights to control their medical care.

The settlement came in the celebrated case of Angela Carder, a vibrant 27-year-old whose 14-year struggle with cancer ended after a forced Caesarean section in 1987. It was the second time in seven months that Carder's death, which some doctors said was hastened by the surgery, led to important precedent in the conflict between fetal and maternal rights.

The first, an April decision by the D.C. Court of Appeals, created a nearly absolute right for a woman to make her own choices for health care, even in rare cases where there is a conflict with the health of the fetus. The settlement announced yesterday, which closed a related civil lawsuit, made it far less likely that similar future conflicts -- at George Washington, at least -- will have to resort to court.

Carder came to George Washington in June 1987 in mid-pregnancy and with advanced terminal cancer. She died two days after the hospital performed a court-ordered Caesarean section -- a desperate attempt to save the premature fetus -- over the objections of her family, her doctors, and the lawyer appointed to represent her.

Lindsay Marie Carder, born after 26 1/2 weeks in the womb, lived less than three hours.

Christine St. Andre, the hospital's administrator, pledged as part of the settlement that the hospital would "virtually never" bring difficult medical decisions to a judge, as George Washington did in Carder's case. Instead, in a policy document reflecting unusual collaboration between courtroom enemies, the ACLU helped the hospital establish guidelines for its newly formed medical ethics committee. Notably absent from the news conference were the hospital's lawyers. The negotiated guidelines emphasize the woman's autonomy, her right to informed consent, and the hospital's need to rely on the views of close relatives or "surrogates" when the woman is not competent to make decisions. The hospital pledged to give all incoming patients a "bill of rights" and practical advice on enforcing it.

"We would say hallelujah," said Morton Lebow, a spokesman for the American College of Obstetricians and Gynecologists, which intervened against George Washington in court. A lawsuit, he said, "is the worst way to make a medical decision."

The settlement announced yesterday also included an undisclosed sum of money for Nettie and Daniel Stoner, Carder's parents. The Stoners had sought $3 million in damages for alleged medical malpractice, wrongful death and violations of Carder's civil rights.

The case ignited national controversy. Though the hospital took no formal position on the surgery in the emergency hearing it requested before D.C. Superior Court Judge Emmet G. Sullivan, its decision to go to court and the manner in which it assembled evidence suggested to feminists and Carder's family that the hospital wished to perform the operation against Carder's will.

Long after Carder's death, in arguments before the D.C. Court of Appeals, the hospital made that position explicit. Vincent C. Burke III, the hospital's lawyer, maintained that because Carder was sure to die soon and the fetus might be saved, the hospital had a right to perform the surgery whether or not Carder agreed.

"Are you urging this court to find that you can handcuff a woman to a bed and force her to give birth?" Judge Frank E. Schwelb asked Burke at the time. Burke, calling it a difficult question, gave a long and rambling answer in the affirmative. The appeals court ultimately disagreed.

Yesterday, the hospital displayed the fruits of a long and painful reconsideration.

"I am not going to defend what Vince Burke said," St. Andre said in an interview yesterday. "That doesn't reflect how we feel at this point. But I don't want to trash the man. We've all learned a lot."

The crucial lesson, according to Terry Thornton, a New York lawyer who represented the Stoners along with Lorna Schofield and the ACLU's Lynn M. Paltrow, is that "you shouldn't wait until a complex medical situation presents itself . . . and then run to a judge because you haven't done your homework."

Paltrow, who runs the ACLU's reproductive rights project, said 23 hospitals in the last 10 years have sought court orders on the treatment of pregnant women's fetuses. Carder's case was the first to be fully briefed and decided by an appellate court, and the first to lead to a malpractice case in civil court.

Yesterday's settlement, Paltrow said, was another first: a carefully negotiated procedure for handling future conflicts out of court.

That procedure, said Susan M. Wolf, an expert on medical ethics at the Hastings Center in New York, is part of a movement toward ethics committees that began in 1976, when the New Jersey Supreme Court had to decide whether to withdraw medical treatment from comatose Karen Ann Quinlan.

"This has been a terrible tragedy for us," said Nettie Stoner, "but positive things have come from it."