Jeremiah Thate was just 3 weeks old when he last gazed at his mother's face -- too young, some experts theorize, to miss her smile or care who held his bottle, changed his diapers or held him close during the time he spent with two women in a squalid apartment building in Southeast Washington.

But his reunion Wednesday night with his parents -- four months after being taken from his Prince George's Hospital Center room -- came just in time, medical authorities said.

The infant was approaching a critical developmental stage that could have made such a separation and reunion devastating.

"It's good that the child is under 6 months," said Dr. Leon Cytryn, a child psychiatrist with the National Institute of Mental Health. "He's not going to be afraid of the parents."

Cytryn, who conducts research on the emotional needs of infants and toddlers, and other area pediatricians and child psychiatrists said that Jeremiah's separation from his parents, Theresa and Robert Thate, happened during a time that the infant could not distinguish well among individuals.

It is a time of self-absorption, they said, when having the basic physical needs met is significant in assuring a happy, secure baby.

"That's the period in which an attachment occurs, it's an emotional bond," said Dr. George W. Bailey, director of inpatient psychiatry at Children's Hospital Medical Center.

But Bailey and other medical authorities said that a very young child can transfer the attachment to other loving adults rather easily. "If it's a good, secure attachment, the child will be able to spread out a little more, become more trusting."

Most infants do not have "stranger anxiety," or fear of people other than those closest to them, until they reach about 6 months.

Jeremiah was found Wednesday afternoon living with two women in a rat-infested, garbage-strewn apartment in Anacostia. But medical authorities said the surroundings themselves should have little impact on the child.

"I don't think the squalor means much," Cytryn said. "Babies can be very well-adjusted in the slums and abused in very plush homes."

The blond-haired infant alternately slept and smiled at his parents and other adults at Holy Cross Hospital where he was taken for an examination shortly after he was found.

Doctors pronounced him in good health, after urine and blood tests and a chest X-ray showed no problems, a spokesman at Holy Cross said.

They said he had no scars, bruises or other signs of injury, beyond severe diaper rash. At 18 pounds, he was considered of normal size and in good physical health and developing normally.

"He was bright-eyed, he was smiling. He was a very happy little baby," said Holy Cross spokesman John Walker.

Yet, the Thate family has questioned whether Jeremiah's emotional needs were met during the abduction. Doctors said that children who do not have their cries answered or who are deprived of attention may eventually show signs of fear of anyone who approaches them, screaming or crying or arching their backs.

"The question is what happened with these other people," Cytryn said.

The two women charged with Jeremiah's abduction were loners who, neighbors said, sometimes behaved erratically. Many thought it was a doll they held close to them on the nights they took walks. It was clear that they treated him, or at least dressed him, like a girl.

For the Thates, the happy return of Jeremiah may need to be tempered by caution, the experts said. A neglected or ignored child may become confused if much attention is suddenly lavished on him.

"They're dealing with a child who doesn't know them. They may overwhelm him with hugs and kisses," Cytryn said.

The tendency is to shower a baby with attention, holding and cuddling him constantly.

But some experts suggest that parents gradually work toward rebuilding the relationship and not immediately or continuously overstimulate a child who is not used to them. Others said the parents should take care not to exclude other siblings during this period.

The Thate case is far from unique. More than 16,000 youngsters, infants through 17, are listed as missing in the United States, according to the National Center for Missing and Exploited Children.

While half of those are old enough to have been declared runaways, 436 are thought to have been abducted by strangers. According to the FBI, 10 newborns have been abducted from hospitals in the past two years.

Yesterday, the FBI reported that it had recovered a baby in South Philadelphia who may be Kendol Kernes, a newborn boy apparently abducted June 18 from Johns Hopkins Hospital in Baltimore.