Nobody else wanted the baby, born to a prostitute and sick with AIDS. How can that be? the two women asked. This baby is an angel. This baby is a blessing. So they brought Sabrina into their home.

The doctors warned them: The girl may only have a few weeks to live. Still, the women bought her toys and hugged her and sang her lullabies. A month passed, then two, then four. The infant grew. She thrived. And the two women, convinced that love conquers all, declared Sa-brina "the miracle baby."In the end, the recovery was temporary. Sabrina, 15 months old, was cremated in her pink and white Easter outfit with black patent leather shoes. For all their car-ing, the women were left with grief. Losing a child is the greatest pain of all, they said.

But during this past year, instead of retreating into remorse, the women have taken in four more infants. Like a small but growing number of foster parents around the country, Yvonne Hardee and Laura Garcia-Pulido of Hollywood, Fla., have opened their homes to children who live under the shadow of AIDS.

The nurturing can be bittersweet, the joys of raising a baby tempered by the possibility of an early death: "With Sabrina, I would sit in the rocker and make memories, you know, concentrate real hard on the exact moment, what she had on, what she did. Who knew when there wouldn't be any more memories to make?" Hardee, 41, said.

Foster care for babies who have AIDS or who are very likely to get it is becoming an urgent national concern. In all the dreariness about acquired immune deficiency syndrome, there is this to add: Pediatric AIDS cases are rapidly increasing.

By 1991, 10,000 to 20,000 children, mostly babies and toddlers, will be infected with the human immunodeficiency virus that causes AIDS, according to U.S. health officials. One of every 10 pediatric beds in the nation will be occupied by a child with the disease.

In the past, children became infected largely through blood transfusions. That danger has been all but eliminated. Babies now get AIDS another way: in the womb, from their mothers.

Most of the new cases result from contaminated needles. More than half the women infected with HIV are intravenous drug users or the sex partners of IV drug users. They are young; they have babies.

The problem is so severe that some cities and states have done studies on the number of babies born with antibodies to HIV. One in every 80 babies in New York City tests positive; one in every 200 in New Jersey; one in 205 in Florida; one in 1,200 in California.

Not all of these infants will get the disease. When a newborn is found to have antibodies to HIV, that may simply mean the antibodies have been passed from the mother's immune system and will disappear as the baby matures.

But if the antibodies are still present after 18 months, then almost surely the baby has inherited the virus. That is true in about 30 percent to 40 percent of the cases, and most of those babies are likely one day to develop AIDS.

In the meantime, parents and doctors can only guess - and wait. Any rash or breathing problem is dreadfully alarming. Any burst of tears can be the foretelling of catastrophe.

Few children are more helpless than these. Often, their mothers are themselves sick with AIDS or hooked on drugs. The babies frequently are neurologically impaired from their mother's substance abuse. Their extended families are usually poor and hard-pressed to care for them.

Without a place to go - even while still healthy - the babies may languish in the enclosed cribs of hospital wards where fluorescent lights shine down on them all day. They get no regular cuddling or love, just occasional visits from nurses who have only a few moments to stay with them.

To rescue these infants from confinement, health officials nationwide have scrambled to set up group homes or, when they can, to enlist foster parents. In most places, the efforts have been encouraging.

"Cities that make it a priority and recruit actively have been fairly successful," said Betty Stewart, a high-level child services administrator in the U.S. Department of Health and Human Services.

But long-term prospects are not good. "You don't have to be Albert Einstein to see that the numbers will soon outstrip the services," said Dr. James Oleske, who runs a program for children with AIDS in Newark, N.J.

To recruit parents, most agencies pay larger-than-normal stipends. In Los Angeles County, for instance, foster parents receive $1,000 a month to care for children with symptoms, more than triple the usual rate.

But the decision to take such sickly, vulnerable babies must come from the heart, not the pocket. It requires the will to endure great personal pain for the sake of a baby born to somebody else, a baby who may die.

"If they catch cold, you worry. Will this become pneumonia?" said Laura Garcia-Pulido. "Chicken pox will kill them. They have no defenses."