Prince George's County Executive Lawrence J. Hogan yesterday reversed his three-year-old practice of refusing to fill vacancies on the county's three hospital boards and hospital commission and announced 30 nominations.

Hogan had not filled the vacancies for the past three years during his attempts to transfer the county hospitals to private management. That attempt failed when the County Council narrowly refused this fall to approve a lease to the hospital-management firm Hogan had chosen to run the hospitals.

Although individual members continued to speak for the boards, the many vacancies prevented the boards from functioning effectively in the past three years, according to Dr. Claire Christman, a member of the hospital commission that oversees all three boards. She has been a longstanding critic of Hogan's failure to fill the vacancies, and has said it was a means of reducing opposition to his lease proposal. Christman was not among those appointed to the commission yesterday.

Hogan sent the nominations, which will fill most of the 43 board vacancies, to the County Council yesterday. The council must formally approve them after public hearings.

"It made no sense to make appointments to the four-year terms if the boards were going to be abolished," said Lawrence J. Hogan Jr., the executive's son and aide in charge of appointments.

Two of his nominations to the 13-member hospital commission are well known antiabortion activists. They are Robert J. Brady Jr. of Bowie, and Walter H. Maloney Jr. of Beltsville. Hogan has tried unsuccessfully to have abortion banned in the county hospitals.

But a number of prochoice proponents also are included in the list of nominees and Hogan's son said the abortion issue was not a factor in the selections.

"He Hogan did not even ask the question," his son said. "I venture to say that most of them do not share that posi-tion . . . . .

"We took it to court and we fought it as far as we could and now it's a dead issue."

Each of the hospital boards has 11 members and their bylaws specify a set number of doctors, nurses, consumers and other members.

The groups are to direct the policy-making of the three hospitals, the Prince George's General Hospital and Medical Center in Cheverly, the Greater Laurel-Beltsville Hospital in Laurel and the Bowie Health Center in Bowie.

Following the defeat of the lease proposal, a group of citizens and county officials formed a committee under the direction of the County Council to explore alternatives to leasing the hospitals. Currently, the committee is preparing a report for the council that recommends the creation of a nonprofit corporation which would then run the hospitals.

The remaining 13 vacancies will be filled in the coming weeks, Hogan Jr. said. He said the delay was due to problems in receiving enough recommendations for the positions.

But Audrey Scott, the mayor of Bowie and a nominee for the Bowie Health Center board, criticized the delay. "I'm disappointed only six names were sent down for the Bowie board . I know there are a lot of people in Bowie who are anxious to serve."