A noted child expert reports a link between extended non-parental care during the first year of life and later insecurity, disobedience, aggression and problems in school.

On the other side, a researcher says her study shows not all parents have the temperament to provide an around-the-clock nurturing environment for their babies, who might actually benefit from an out-of-home setting.Both agree the current U.S. system for raising baby needs such reforms as greater parental leave options, part-time work opportunities and improved availability and affordability of quality child care.

With one of every two American mothers of children under 1 working outside the home, the great debate over whether day care harms or benefits infants is growing louder and affecting more families than ever before.

The latest findings were reported at a recent annual meeting of the 36,000-member American Academy of Pediatrics.

A foremost child researcher warned that a series of recent studies provide "disconcerting evidence" of an association between 20 hours to 30 hours a week of non-parental care before a baby's first birthday and increased risk of an insecure infant-parent bond, aggression, disobedience and noncompliance during the preschool and elementary school years.

"We don't know if this is promoted by day care or by other circumstances in the family," Jay Belsky, professor of human development at Penn State University, said in an interview. "It does raise serious concerns about the development of a large number of children growing up in America today."

Of mothers who work outside the home, the majority return from maternity leave within the first four months of their child's life, Belsky noted.

"We have documented effects that appear to be caused by child care but may be attributable to children's care histories, temperaments, families and other circumstances," said Sandra Scarr, commonwealth professor and chairman of the psychology department at the University of Virginia in Charlottesville.

Much of the research on infant day care contains no direct, on-site assessments of quality and focuses on the mother-child attachment as the only measure of children's adjustment, she said.

"The fantasy that mothers at home with young children provide the best possible care neglects the observation that some women at home full-time are lonely, depressed and not functioning well," Scarr said. "Home care does not promise quality child care."

That may be true, Belsky said, but "we found some children show a lack of sensitivity and concern for the needs and feelings of others, which might be due to the insufficient attention they received earlier."

Belsky studied 140 families from before the birth of their first child through the youngster's fifth birthday.

At the end of the first year, Belsky's team found, children cared for by outsiders showed more insecurity in the attachment to their parents than youngsters who had spent the first year with their moms or dads.

To measure "insecurity," researchers separated babies from their parents, then observed how each child greeted the mothers and fathers upon their return. Children who avoided or ignored their parents or who, if upset, were difficult to comfort were judged insecure.

Some scientists dispute these findings, contending the babies' reactions reflect "precocious independence," rather than insecurity.

"Our data, however, go way beyond this study," Belsky said. "We also have evidence of later disobedience and aggression that cannot be explained away."

In several studies, researchers found unusual aggression and disobedience among 2-to-8-year-olds who had been cared for outside the home.

"They are not psychopathologically impaired, but their teachers, parents and peers all report seeing them fighting, hitting, kicking, punching and screaming more than other children and being far less inclined to follow adult rules and regulations," Belsky said.

"The question becomes, `Is there something about the social development of this child that is being undermined or is this child simply more assertive and independent?' What risks are we willing to take while awaiting the answer?"

The revolutionary changes in child care over the past decade have invalidated the bulk of scientific data on the subject, Belsky said. For example, much of the information had been gathered at select, high-quality university centers.

"That may have been typical of 10 years ago," Belsky said, "but it certainly isn't the average out-of-home setting for babies today."

Fewer than 15 percent of infants are sent to formal centers, he said, with most families opting for babysitters, relatives or family day-care homes.

"The slow but steady trickle of scientific findings reflecting the current situation indicate extensive non-parental care in the first year is associated with a series of behavior patterns that raise concern in my mind," said Belsky, who in 1978 authored the most comprehensive review to date of scientific data on child care.

Belsky and Scarr agree any inferences that all day care is bad and, therefore, no legislative relief is needed "are plain naive and misguided."

Both decry Congress's defeat in 1988 of the Act For Better Child Care Services, which would have helped parents to pay for child care and states to expand children's services and facilities, improve the licensing and training of care providers and provide better information and referral services.

"The kind of care America makes available for our babies is in no one's best interest," Belsky said. "Something is fundamentally broken and needs to be fixed."

He defined three major problems: no parental leave options; no viable part-time job opportunities for parents of infants, and limited quality care.

Belsky urged Americans to follow the Swedes, who have six-month paid parental leaves, job security for new mothers and fathers and children's centers abundant in material and human resources.