Legal experts on both sides of the abortion controversy today questioned whether medical judgments of fetal viability -- the point at which a fetus can survive outside the womb -- should continue to be the primary standard for legal decisions on abortion.

Medical advances in saving premature babies at earlier stages have led to predictions of an inevitable collision between the rights of the mother to have an abortion and the unborn fetus to survive.

"There is a strong argument that viability's importance has, in fact, been inflated," said Nancy Rhoden of Ohio State University Law School. "The question is whether viability is so important that constitutional law should blindly follow it.

"Only in the abortion arena has the Supreme Court made medical technology the master of women's constitutional fate, and in doing so it has made a serious mistake."

Rather than pushing the abortion threshold back as medical advances in saving fetuses occur, Rhoden said, the court should set a legal time standard in the second half of pregnancy "beyond which states could not prohibit abortion."

Rhoden appeared on a panel and at a news conference today at the 151st annual meeting of the American Association for the Advancement of Science.

Brigham Young University Law School's Richard G. Wilkins, who formerly served in the Justice Department in the Reagan administration, also questioned the reliance on medical decision-making. But Wilkins had a different solution: Turn the abortion issue back to state legislatures.

"Under current law, states may not enact laws that deviate from accepted medical practice," he said. ". . . Why should medical and scientific boards serve as governing bodies of a democratic society?"

The Supreme Court recognized women's constitutional right to abortion in the historic Roe v. Wade decision in 1973 but made it contingent, in part, on fetal viability, defined as "that stage of fetal development when the life of the unborn child may be continued indefinitely outside the womb by natural or artificial life-supportive systems."

At that time, the threshold of viability was around 28 weeks of pregnancy and only about 50 percent of babies born at that point could survive. Today the threshold has dropped to about 24 weeks, and nearly all 28-week-old infants survive.

At the same time, abortions in the second trimester of pregnancy have become safer.

Subsequent court decisions have reaffirmed the general Roe v. Wade approach, but a 1983 dissent by Justice Sandra Day O'Connor predicted a collision between women's rights and those of fetuses.

"As medical science becomes better able to provide for the separate existence of the fetus, the point of viability is moved further back toward conception," O'Connor wrote.

While Wilkins supported this belief, Rhodan said the outlook is not for a "dramatic alteration in time of viability, but rather slow, incremental changes that may push the threshold back by a week or two."

Nan Hunter of the American Civil Liberties Union, a strong advocate of women's right to abortion, complained that the issue of viability has been "overblown" by abortion opponents.

She noted that the percentage of late abortions has decreased dramatically over the past decade, so that 99 percent of the more than 1.3 million abortions each year occur by the 20th week of pregnancy, with half occurring in the first eight weeks.

Those who get abortions later tend to be young women who did not have good access to health care, women who discover fetal birth defects through genetic testing, or women with health problems, Hunter said.

"There will probably always be some need for late-term abortion," however small, she concluded.

Dr. Robert Hayashi, the head of obstetrics at University of California, Los Angeles-Harbor Medical Center, and former head of the Society of Perinatal Obstetrics, said the "horns of the dilemma" now are at 24 weeks of pregnancy, but he does not foresee dramatic changes in survival at much earlier stages unless scientists develop an "artificial womb."

The Supreme Court has agreed to review cases next fall that involve attempts by Pennsylvania and Illinois to regulate abortions.