For almost four months, the Supreme Court has had before it a ruling in a bizarre abortion case from South Carolina.In the ordinary course of things, the justices might have disposed of it weeks ago. Instead, they recessed last Monday without taking action, thus putting the case off until the term starting in October.

As is customary, the court gave no reason for dealying disposition. Even so, it implicitly made one thing clear: after making two major decisions on the volatile issue of abortion, in 1973 and in 1977, the court has yet to settle troubling questions about when a fetus becomes, in legal parlance, "viable" - This is the question that is central in the South Carolina case.

Five years ago, the court indicated that a fetus is either viable, that is, "potentially able to survive outside the mother's womb, albeit with artificial aid," or it isn't.

In 1974, however, Pennslyvania passed a criminal stature requiring physicians to try to save the lives of fetuses that "may be viable." A panel of three federal judges held that the law improperly established a third category of viability.

Last March, the Supreme Court agreed to hear an appeal of the panel's ruling next fall or winter. Meanwhile, apparently, the court is holding off action in the South Carolina case.

In that case, the state has petitioned the court to let it try a physician for murder because an abortion he performed resulted in the birth of an enfeebled infant that survived in a hospital intensive care unit for 20 days and then died.

The state wants the court to overturn a holding by the 4th U.S. Circuit Court of Appeals last November that prosecutor James C. Anders "was not proceeding in good faith" when he obtained indictments - for criminal abortion as well as murder - of Dr. Jesse J. Floyd of Columbia.

Seeing "no possibility" of Anders winning a conviction "that could have been constitutionally sustained," Chief Circuit Judge Clement F. Haynsworth Jr. and the doctor's lawyer cited these bizarre aspects of the case:

Anders admittedly obtained the indictments on the basis of his misreading an accurate article in a news magazine, of a freshman law student's summary of a crucial 1973 Supreme Court opinion that the prosecutor hadn't read for himself, and of a state law whose draftsman had misinterpreted the same opinion.

In the opnion, in the famed case entitled Roe vs. Wade , the court dealt with the perplexing question of when a fetus becomes viable.

Viability "is usually placed at about seven months (28 weeks) but may occur earlier," Justice Harry A. Blackmun wrote for the 7-to-2 majority. He said that a fetus may be viable starting with the 24th week but did not try to pinpoint a time.

Whenever viability may begin, Blackmun said, until it is reached "the attending physician, in consultation with his patient, is free to determine, without regulation by the state, that, in his medical judgment, the patient's pregnancy should be terminated."

Under the Constitution, Blackmun said, a fetus that isn't viable is neither alive nor a person, but after it is viable a state can assert a compelling interest in protecting its life.

The South Carolina case began in 1974 when a woman identified as Louise Doe, 20, describing herself to a social worker as "desperate, decided to have an abortion.

Floyd performed the abortion at Richland County Memorial Hospital. According to his notes, he estimated, apparently accurately, that Doe would be 25 weeks pregnant at the time of the abortion, although Doe testified that the doctor had told her she would 21 to 23 weeks pregnant.

The state abortion law, erroneously reflecting a certitude missing in Roe vs. Wade flatly declares a fetus viable after 24 weeks. Yet, says Dr. Theodore King of Johns Hopkins School of Medicine, a leading obsterician-gynecologist who filed an affidavit in the case, it is "untenable" to presume that "every 25-week fetus will survive."

During the 20 days in which Doe's baby, a boy, remained alive, he suffered from bowel difficulties that led to peritonitis.

He was taken quickly after birth to the hospital's neonatal intensive care unit. After alternating between crisis and relatively sound health, he died from complications attributed to pre-maturity.

Hospital authorities sent the record to the then-prosecutor "for whatever decision your office would desire to make." After taking office, Anders decided to get indictments, which were formally announced a day after a federal judge had granted Floyd's petition to block them.

Upholding the federal court, the appeals court said that if Anders had read Roe vs. Wade, "he would have known that the fetus in this case was not a person whose life state law legally could protect." It "should have been obvious" to him that he couldn't get a conviction that would stand up, Haynsworth wrote.

He said that it "cannot have been in good faith" for Anders to have sought indictments based on his reading of an article in Newsweek magazine (which was accurate and which the prosecutor termed "significant"), and on the summary of Roe that he had requested from the freshman law student and that turned out to be "quite misleading."

In seeking Supreme Court review, state Attorney General Daniel R. McLeod argued that the 4th Circuit decision "permits the destruction of fetuses which, under Roe vs. Wade, are viable and the proper subject of compelling state interest."

Moreover, McLeod said, the decision "denies protection of law to infants born alive after an abortion," because it apparently presumes "that, as a matter of law, a fetus that dies after an abortion is automatically "non-viable."

In a reply brief, the physician's lawyers contended that "there is no rationale answer to the question of how one can find murder when a fetus temporarily survives an abortion and is immediately treaded with all heroic efforts."

They charged that the prosecutor, in seeking the indictments, "suppressed an apparently ignored" important evidences "that an abortion was necessary for the psychological well-being of Louise Doe."

What the Supreme Court will do in the case almost certainly won't be known until it acts on the appeal filed by Pennsylvania in the other case.

At issue here is the Pennsylvania Abortion Control Act of 1974. The law says that before undertaking an abortion, a physician, relying on his "experience, judgment and professional competence," must use the care necessary to protect the life of the fetus "if there is sufficient reason to believe" that it "may be viable," and if he will not thereby endanger the mother's health.

In a controversial decision that the state seeks to have reversed, a panel of three judges declared the law unconstitutional. The panel said that Roe vs. Wade had recognized only two time periods, for fetuses, one before and the second after viability. But the panel said, the Pennsylvania law "tends to carve out a third period of time of potential viability," which, a witness for the state testified, runs from 20 to 26 weeks.

"It is clear in carving out this new time period labeled 'may be viable' the state is regulating abortions during the second trimester," the panel said. It could do this only in the interest of material health, but does not claim to be serving this interest, the panel said. "Clearly, the state seeks to justify this provision in furtherance of its claimed interest in protecting potentially viable fetuses."