Within only a few weeks, three infants -- one in the District, one in Prince George's County and another in Baltimore -- have perished. In each case, a mother has been charged or implicated in the deaths. Each case is bizarre -- stabbing, beating, smothering -- each unspeakably painful to hear or read about.

Yet, the experts tell us, homicide, usually at the hands of a parent or putative caregiver, is among the leading causes of death in children. Infancy is the time when children are at the greatest risk of death from what the experts dispassionately call "nonaccidental injury."

One out of 22 murder victims in the United States is a child killed by one of his own parents.

Joyce Thomas, chief of the child protection division at Children's Hospital National Medical Center, sees hundreds of abused and suspiciously injured children every year -- some 600 injured and another 800 apparently abused sexually. Homicides are rarer, but inevitably there are six or seven every year.

The cases are uniformly agonizing, and, she says, infant homicide is difficult to generalize about, even harder to predict. "Sometimes," she sighs, "I wish I had a magic wand to wave over some of these families."

Thomas sees a great deal of the cause of these tragic events as one of "unsettling panic" in the parent, panic about parenting itself, along with an inability to express this crushing lack of self-confidence.

"You are talking about infants being extremely vulnerable to parents who have an extremely distorted understanding of parenting and parenthood and have not been able to articulate" what is wrong.

Thomas recalls a woman who "years ago" described how her recurring panic drove her to abandon her 2-month-old infant.

"It is the same kind of discomfort with parenting," says Thomas, "but they really don't want any harm to come to the baby.

"This woman described to me how she just couldn't cope with being a mother. It was too frightening, too demanding. She had thought about it a lot over the years and although she'd had a lot of advice about parenting, she was just confused. As she tried to take care of her baby, little things, normal things became overwhelming -- the baby crying, an episode of diaper rash. She had no place to go, no one to help.

"One day she took her baby and put him in a public telephone booth. She took the number, went to another phone around the corner and rang the number so someone had to come answer -- and find her baby.

"She never saw him again. When she told me the story several years later she still had this extreme unresolved guilt because she 'knew' she was a failure as a mother. And she never had another child."

Based on her own experiences and a review of what research literature is available on the subject, Thomas feels that "similar panic occurs with those who deliberately or systematically, in seemingly malicious ways victimize very young infants." The difference, of course, is that "they don't just want the baby to be found. They just want the baby removed."

Nobody wants to believe that a parent could deliberately injure, much less kill, a baby. Nobody, including many physicians -- family doctors, emergency room personnel, medical examiners. Sometimes it's not obvious that a child has been abused, or that a death was a killing. One study of "subtle" child abuse in six infant deaths was designed, its authors write, "as a reminder that adequately nourished children can still be homicide victims when they do not have broken bones . . ."

Dr. Eli H. Newberger, a leading authority on child abuse and child homicide -- subjects that have only in the past few years been thrust upon the public consciousness -- believes there is a great deal more out there than ever is brought to the attention of authorities.

"Physicians, after all, are human," says Newberger, "and like everyone else, they find profoundly distressing the possibility that parents could kill an infant. Very frequently physicians may deny, and by this I mean literally in the psychological sense -- pushing out of their minds the conscious acknowledgment that the injuries that they see are attributable to someone's hitting a child."

"One sees this all the time," says Newberger, a pediatrics professor at Harvard Medical School and director of the Family Development Center in the Boston Children's Hospital Medical Center. "Especially in the specialists who deal with trauma -- neurosurgeons, orthopedists and surgeons."

"In addition," Newberger says, "we have a system in medicine where decisions as to whether death is a homicide are relegated to specialists and offices that may not necessarily have sufficient sensitivity or capacity to deal with a family."

For instance, he notes, medical examiners often pay no attention to social service records to see if there has been a record of other violence in the family -- between husband and wife, for example, "an important risk factor" for fatal child abuse.

Moreover, says Newberger, as a general rule, medical professionals do not like to make diagnoses unless they feel there is a possibility of a subsequent treatment, "so doctors over the years have ignored the problem of child abuse because they don't feel anything can be done. I think this generalizes to homicides."

Virtually all of the research and clinical specialists on this troubling, often tragic, problem agree that hard data is hard to come by. And its causes and especially techniques for its prevention remain elusive. After all, says Newberger, "doctors have spent the last 20 years trying to pry their eyes open to this problem."

The relatively small body of specialists in this area have tended to view child murder as a complication, as it were, of child abuse. At least one recent study, however, suggests that women who actually kill their infants are psychologically distinct from abusive mothers, with the "filicidal" mothers more likely to be suffering from major psychiatric disorders. At least, the study concludes, "the risk of fatality as a complication of child abuse increases significantly when mental illness is present in the mother."

Newberger believes that all child murder involves a "psychological disturbance of a very particular kind. I think it probably has more to do with a serious compromising of a parent's ability to protect the child from the angry feelings most parents will have.

"I think most parents can rein in their angry impulses and so do not do serious damage to their children. But there is something uniquely horrible in those situations where the parents' inability to check themselves is so profoundly compromised." Drug use and chronic stresses such as poverty can make it worse.

"Infants, after all, are very fragile," notes Dr. Katherine K. Christoffel, a Chicago pediatrician who has studied the problem for some years and is one of the top researchers in the field. "You can shake a 10-year-old in a rage and nothing much will happen. But shake an infant like that and you can cause fatal brain hemorrhages."

Her findings support a thesis she published last year in the American Journal of Public Health that difficult infants can provoke anger in the best of parents. When the frustration erupts into violence, the infant's frailty makes him particularly vulnerable.

Thomas, Newberger and Christoffel agree that the incidence of abuse and fatality is underestimated in higher socioeconomic populations principally because it is less likely to be reported for what it is. Newberger headed a national study last year which clearly demonstrated that in a representative sample of hospitals, the determining factors in whether or not a trauma was reported as child abuse were race and income of the parents, rather than the severity of injuries to the child.

And they agree, too, that a major problem is the lack of support systems for the isolated, desperate parent who is unable to cope.

It is, says Christoffel, "the ultimate sadness," that a parent, driven to cope within "the confines of a single little life," may see nothing but violence as an option. Resources

Children's Hospital National Medical Center is expanding its Parent And Child Enhancement (PACE) program to offer support, parenting classes, respite and other help to troubled parents. Participants will be screened for need. Write PACE, Department of Child Protection, Children's Hospital National Medical Center, 111 Michigan Ave. NW, Washington D.C. 20001. 745-5683.