Prosecutors had asked last week that the autopsy results be unsealed after extensive news leaks of the autopsy results. Among the details reported were that loops of plastic were found around the fetus' neck.
Prosecutors suggested the leaks have given a misconstrued view of the case and argued that if the entire report is released the public would get a more balanced impression, reports CBS News Correspondent Steve Futterman.
Analysts said the autopsy results could be used to bolster a defense argument that Peterson was kidnapped by a satanic cult.
Peterson's husband, Scott Peterson, 30, has pleaded innocent to two counts of murder for allegedly killing his wife and son.
Laci Peterson, 27, a pregnant part-time teacher, disappeared just before Christmas. Her body and the body of her unborn son were found in mid-April on the shore of San Francisco Bay. Scott Peterson was arrested shortly after the bodies were found and was charged with double murder.
Superior Court Judge Al Girolami last week ordered that the leaks stop and indicated he would consider a gag order to stop the prosecution and defense teams from talking to the media. He said releasing the autopsy reports could hamper the investigation into Laci Peterson's death and prejudice public opinion before her husband is tried for the murder.
The autopsy details confirmed by an Associated Press source close to the case on condition of anonymity included that 1 1/2 loops of plastic were around the fetus' neck and a significant cut was on the fetus' body.
Prosecutors have said they would support some form of a gag order, while defense attorney Mark Geragos said in court papers that he opposes any effort to curtail discussions about the case.
Girolami on Friday also set a June 26 date to rule on defense motions regarding wiretaps of Scott Peterson's phone calls.
Scott Peterson's lawyers want the judge to toss out the results of two wiretaps that monitored thousands of his calls after his wife's disappearance.
During the court-approved wiretaps, the first of which began two weeks after Laci Peterson vanished, police logged 3,858 phone calls made to Scott Peterson, according to court papers.
Some of those conversations will be questioned by defense lawyers, who claim police eavesdropped on protected conversations between Scott Peterson and his lawyer.
A judge approved the wiretap of Peterson's phone Jan. 10 after prosecutors showed there was probable cause to believe a crime was committed and the wiretap would help them gather evidence they had not been able to find through normal means. They discontinued the surveillance Feb. 4 after it no longer produced results.
A second wiretap was started April 15 after the remains of a woman and fetus, later proven to be Laci Peterson and her unborn son, washed ashore.
The judge on Friday also rejected requests by reporters to listen to wiretaps of phone calls they had made to Scott Peterson.
Attorneys representing 22 reporters had asked to review the tapes of their calls to Peterson so they could determine if they might be barred from becoming evidence. The lawyers said the conversations were protected under the California Shield Law, which protects reporters from turning over unpublished work.
Girolami said he did not think journalists were entitled to any privilege protecting their phone calls. He did, however, delay for 10 days the release of the tapes so reporters could appeal the ruling.