Antiabortion activists in California are collecting signatures for a ballot initiative that would shift state abortion funds for poor women to programs for handicapped children, a measure that national abortion-rights leaders said could be a severe blow.

The "Children's Fund" initiative, which has won support from several churches and many parents of disabled children, would cut off the $30 million spent each year for about 85,000 state-funded abortions and use the money to help handicapped children and premature babies.

The initiative also would allow the state to pay for abortions when the mother's life is in danger, a provision that makes it even more politically potent in its opponents' eyes but has caused a split in the antiabortion movement.

"It will be a serious, major national battle for both sides," said Nanette Falkenberg, executive director of the National Abortion Rights Action League in Washington.

The initiative's language is "politically pretty astute" and carries unusual impact coming from a trend-setting, media-laden state such as California, Falkenberg said. Abortion-rights leaders estimate that each side may spend $2 million to $6 million if it reaches the ballot.

"You know what they say: Liberals care about kids after they're born but not before, conservatives care about kids before they're born but not after. We want to care about kids at every stage of their development," said Wayne Johnson, a Sacramento political consultant who helped pass the 1982 "Victims Bill of Rights" initiative and is working with the Children's Fund group.

The California initiative, aimed at next June's ballot, could significantly influence antiabortion efforts in the other 12 states where publicly funded abortions are allowed, Falkenberg said. She said antiabortion activists failed to pass an anti-public-funding measure in Washington state last year but won narrowly on the Colorado ballot and are considering similar efforts in Oregon, Arkansas and Massachusetts.

Maryland and the District subsidize medically prescribed abortions for women on welfare. In Virginia, state funds can be used only for abortions in cases of rape, incest, severe deformity of the fetus or danger to the life of the mother.

The two-part Children's Fund initiative here is proposed as an amendment to the state constitution, in an effort to stymie attempts to kill it in court. The state Supreme Court has ruled that denying abortions to poor women eligible for the state's Medi-Cal health-care program would violate their right to privacy under an earlier amendment to the state constitution and a series of federal and state court decisions banning government interference in an individual's sex life.

Johnson said initiative supporters hope to gather more than double the required 630,129 signatures by Dec. 19. State Supreme Court Chief Justice Rose E. Bird and several justices face reconfirmation votes on the November 1986 ballot and may refrain from keeping the initiative off if public support for it seems strong, Johnson said.

Renate Penney, leader of the Children's Fund campaign, was once a full-time staffer for the American Life Lobby in Sacramento but could not persuade the Virginia-based antiabortion group to support the initiative. Susan Sassone, an Orange County resident on the American Life Lobby board, has filed a separate proposed initiative that would ban state funds "for the killing of innocent human individuals from fertilization until natural death."

Although statistics are inconclusive, Falkenberg said even when states have cut off public funding for abortions, most poor women who want an abortion "get the money somewhere."

"Usually it means the kids they already have don't get the shoes they need or don't get as much food that month," she said.

In certifying language accompanying the Children's Fund initiative, the state attorney general's office insisted on a phrase indicating that the measure could mean more costs to taxpayers. "They argued that fewer abortions might mean more children on welfare," Johnson said.