Activists opposed to the 1973 Supreme Court decision legalizing most abortions will stage their ninth annual March for Life here Friday, leading thousands of protesters up Pennsylvania Avenue from the White House to the Capitol.

The march, which drew 50,000 to 60,000 people last year, according to police estimates, will start from the Ellipse at 1 p.m., wind around the White House grounds and end at the west side of the Capitol. Traffic on Pennsylvania Avenue will be diverted around the march as it moves toward the Capitol.

Organizers are pushing for a new "Human Rights Amendment" to the Constitution that would generally forbid abortions and provide for "equal care" for both mother and child in a difficult pregnancy--a shift in language from previous proposed amendments that specifically permitted abortions when the mother's life was endangered or did not address the issue directly.

The new amendment, introduced by Sen. Jesse Helms (R-N.C.) and others, "says that the doctor can do anything reasonable . . . to help save the lives of both the mother and the baby," said March for Life president Nellie J. Gray yesterday. She said the amendment has won support from the boards of all "major prolife organizations" in the country. This unanimity has been lacking in the past, she said.

Gray said that the demonstrators will assemble at noon Friday in the Ellipse just south of the White House for music and a round of speakers including Helms, and then step off at 1 p.m. for the march. The marchers will disperse at the Capitol and go to the offices of senators and representatives to lobby for the amendment.

Gray said thousands of demonstrators have chartered buses from as far away as New England and the Midwest, and others are flying in from Houston and points in North and South Dakota.

Kathleen Sweet, march organizer and executive director of Episcopalians for Life, said that based on 1979 federal Center for Disease Control abortion estimates, March for Life leaders have projected there will be 2 million abortions this year in the United States. "It's a holocaust," she said. "People need to wake up more to this."