Kenneth William Shields, one of three Washington area men charged in a rash of abortion clinic bombings in 1984 and early this year, pleaded guilty today in federal court to conspiracy in the bombings.

Shields, 34, an employe of a wire and fabric company in Warrenton, Va., is the last of the three men to plead guilty or to be convicted in the case. Thomas Eugene Spinks, 37, of Bowie pleaded guilty to conspiracy May 3, and Michael Donald Bray, 32, also of Bowie, was convicted of conspiracy and related charges by a federal jury last week.

Sentencing for Shields, who until recently lived in Laurel but now lives with his parents in Silver Spring, was scheduled for July 12 by U.S. District Court Judge Joseph H. Young. He faces a maximum of five years in prison, $10,000 in fines and an unspecified amount in restitution for damage to 10 abortion clinics and related facilities firebombed in Maryland, Virginia, the District of Columbia and Delaware. He remains free on $25,000 bond pending sentencing.

Federal prosecutors have said that there are at least seven other suspects in the bombings, but Shields, Spinks and Bray are the only ones arrested so far. Prosecutors would not indicate if more arrests are expected.

Shields, a tall bespectacled man in a three-piece blue suit, stood quietly before Young today as he acknowledged his role in the bombings.

In a formal statement of facts read to the judge, prosecutor Robert B. Green said Shields, a religiously fervent foe of abortion who had a "background in chemistry," provided Spinks with textbooks and manuals on building explosive devices. Green said Shields also helped Spinks buy sulfur, sodium chlorate and other ingredients through the use of phony names and mail-order business firms, including one called "Sur-Co," short for "Survival Chemical Co."

Prosecutors have said that while Shields helped assemble the bombs and Bray helped select and monitor the clinics targeted for bombing, Spinks carried out the actual bombings.

After pleading guilty in the case, Spinks testified for the government at Bray's trial, saying Bray accompanied him to the bombings of clinics in Dover, Del., and Norfolk, but thereafter took a less direct role.

Testimony at Bray's trial indicated that Spinks knew both Bray and Shields but Bray and Shields did not know each other. All three men were described in testimony as active members of evangelical church groups opposed to abortion.

Shields originally was indicted on two counts of conspiracy and three counts of possessing unregistered destructive devices. He pleaded guilty today to one count of conspiracy to obtain and assemble destructive devices. The other counts were dismissed.

The 10 bombings, most of them done at night or at dawn, did extensive damage to the clinics, as well as to unrelated businesses adjacent to the clinics. There were no injuries.