Abortion rights advocates here say that the filling of criminal charges against a doctor who superivised a Sept. 6 abortion which resulted in a live birth was politically motivated.

On Wednesday, Douglas County prosecutor Donald Knowles charged Dr. C. J. La Benz, 31 of the University of Nebraska medical center faculty, with performing an illegal abortion and failing to care for a live fetus.

La Benz was booked, fingerprinted and photographed at Omaha police headquaters and released on his own recognizance. He was ordered by a municipal court judge to appear for a preliminary hearing Oct. 29.

The doctor was subsequently suspended from the hospital's abortion staff pending an investigation.

The charges carry a combined potential penalty of 10 years in prision and a fine of $20,000.

The physician's attorney, Lawrence Batt, and National Organization for Women official Sandra Skorniak accused Knowles of bowing to pressure from abortion foes.

Anti-abortion forces in heavily Catholic Omaha held memorial services for the fetus, and former state labor commissioner Jerry Chizek began an initiative drive to amend the state constitution to prohibit direct or indirect use of state funds for abortion.

On the recommendation of state Sen. Bernice Labedz of Omaha, who is also a local aide to Democratic U.S. Sen. J.J. Exon, the University of Nebraska board of regents voted unanimously to prohibit nontherapeutic abortions at the medical center. The medical center had been the only hospital or clinic in the state that permitted abortions in the second trimester of pregnancy.

Batt says Knowles had ample information to determine that La Benz was innocent of any wrongdoing. "The politics of abortion probably motivated the filings," Batt said.

Yet at least one anti-abortion leader believes the county should have filed homicide charges. "The man is a cold blooded murderer," said state Sen. Patrick Vendittte of Omaha.

Prosecutor Knowles, responding to attacks from people on both sides of the abortion issue, said, "There was no political pressure on me. I have to prove what I allege, and I filed what I felt I could prove in court. That's my job."

Many anti-abortion activists hailed Knowles' action. "I'm very, very happy that it has come to this point," said Sen. Labedz.

NOW's Skorniak said she feared the political implications in 1980 of the medical center abortion. Neither of Nebraska's U.S. senators nor the governor must run next year, but spokesmen for anti-abortion forces have said they will be active in stae legislature and U.S. House races.

"I can see the great pictures of two-pound fetuses on the bill boards now," Skorniak said, adding that the abortion and live birth in question would cause politicans to cave in to the demand of anti-abortionists.

LaBenz has said that he estimated the woman involved in the abortion was 19 to 20 weeks pregnant. Following a saline injection, the woman expelled what was expected to be a dead fetus. No one was attending the woman at the time, and a nurse found the infant 15 minutes later.

La Benz said the nurse then clamped and cut the umbilical cord, and took the infant to the delivery area where it was bathed, baptized, wrapped in a blanket and placed in a warmer. The infant lived for 2 1/2 hours.

La Benz said another doctor at the scene advised him that the infant's chances of survival "were so poor that heroic measures were not warranted."

Nurses who attended the patient and infant following the abortion were reportedly so unsettled by the experience that a counselor was brought in to talk to them. Nurses have expressed resentment that they, rather than the doctor in charge, have to attend patients during abortions.