A Pittsburgh, Pa., pathologist testified yesterday in Boston that the fetus Dr. Kenneth C. Edelin is accused of killing breathed before it died, and Edelin's defense quickly sought to discredit the witness.

Dr. John F. Ward said that slides of a cross-section of lung tissue from the dead fetus revealed a "lack of uniformity" in the expansion of the air spaces, which he said was evidence of respiration of air by the fetus.

Prosecution testimony continued yesterday as Judge James P. McGuire declined to rule on a defense motion to dismiss the case until he has read recent U.S. Supreme Court rulings concerning the issue.

The defense contends that there was unconstitutional discrimination against women in selecting the grand jury that returned the Edlin indictment.

Edelin is charged with manslaughter in Suffolk County Superior Court in connection with a hysterotomy operation he performed on a pregnant woman on October 3, 1973, at Boston City Hospital.

Prosecutor Newman A. Flanagan, assistant district attorney, alleges that Edelin allowed a "male child" to be born "detached from the mother" in the course of that operation, and then permitted it to die.

The prosecution is expected to rest its case today.

Under examination by Flanagan, Ward testified that in a stillborn fetus air cells in the lung are uniformly expanded with fluid secreted by the lungs.

Up for Air

Ward said that slides of lung tissue from the fetus involved in the Edelin case displayed collapsed, partially-collapsed and expanded alveoli, or air spaces. He concluded that the state of the lung cells was due to respiration of air by the fetus before it died.

William P. Homans Jr. '41, Edelin's attoney, was developing an intense criticism of Ward's argument when McGuire recessed his court at 4 p.m.

Homans established that a fetus undergoes "distress" when the placenta, its connection to the mother, is separated from the uterus, and that under such distress a fetus might begin to inhale and exhale the amniotic fluid that surrounds it within the amniotic sac.

In the involved hysterotomy operation, Edelin cut the uterus, then used his hand to separate the placenta from the uterine wall.

Ward resisted Homans's efforts to establish that the presence of fluid in the lungs was due to inhalation of amniotic fluid.

However, Ward acknowledged under cross-examination that he could not be sure that the fluid in the lungs was secreted by the lungs, as he indicated initially.