A 17-year-old Long Island girl, Shanta Clark, delivered her baby in her bedroom and stashed him in a closet for three weeks, feeding him before and after school.

The details of Shanta's pregnancy and the aftermath stunned New Yorkers: How did she manage to carry, deliver and care for the baby without raising eyebrows?

Even more perplexing: Why?

"There's one word for this - fear," said Dr. Michael Silverstein, an obstetrician at NYU Medical Center. "These kids are petrified, and they're not thinking."

Linda Smart-Smith, director of Planned Parenthood of New York's Brooklyn clinic, said it's not unusual for teen-agers to wait until just two weeks before they deliver to admit they're pregnant.

"I had a 14-year-old whose mother brought her to a city hospital, which sent her to us," Smart-Smith said.

"She was 39 weeks pregnant, but she kept denying it. She said, "No, no, no. I'm not.' She was terribly, terribly afraid."

That scenario sounds awfully familiar to Alan Hilfer, a psychologist at Maimonides Medical Center in Brooklyn who is treating another 14-year-old in denial.

"No one was aware this girl was carrying a baby until her eighth month," Hilfer said. "She had no plan, no idea what she would do. She essentially was thinking something miraculous would occur.

"Of course, she had the baby. But even today, in a discussion of birth control, she denied she could possibly become pregnant again. She said, "It'll never happen. It was just that one time.'"

Fortunately, Smart-Smith's and Hilfer's young patients got help before they gave birth - ensuring a safe delivery and medical attention for the newborn.

But others have kept the fantasy going until they were in labor:

Eighteen-year-old Melissa Drexler of New Jersey allegedly strangled and suffocated her infant son and dumped him in the trash last June after secretly giving birth in the bathroom at her high-school prom.

College freshman Amy Grossberg hid her pregnancy until she went into labor, giving birth in a Delaware hotel room. The New Jersey teen and her sweetheart are charged with killing their newborn son and tossing him in a Dumpster.

Brooklyn College student Karlie DiTrapani is charged with giving birth in her bedroom in June, then wrapping her tiny son in plastic and stuffing him in a dresser drawer.

A 15-year-old East Flatbush girl delivered her daughter in the bathroom in June and then hurled her out a fourth-floor window, police said.

A 20-year-old Bronx woman, Bibi Khan, was accused of stuffing her newborn son into a plastic bag and leaving him behind her toilet to die in June.

Forensic psychologist N.G. Berrill of John Jay College of Criminal Justice said concealed pregnancy is the fruit of ambivalence.

"Many of these girls feel neglected, and carrying a baby to term and having something to call their own is wish fulfillment

"But there's also utter fear of what their friends and parents will say," he said.

"They're frozen, and in the meantime, a child develops inside them."

Smart-Smith said many girls don't see abortion as an option.

"Some of them don't really understand what it is, so they're scared of it. Some of them come from religious homes.

"Some are afraid their boyfriends will leave them if they have an abortion. Some of them believe the myths - that they'll never be able to have a baby again," she said.

The result, in some cases, is that the mom-to-be decides to wait until it's too late to have an abortion. But then she gets scared her parents will be mad she waited so long, so she continues the charade.

Some parents, in an effort to keep their daughters out of trouble, deliver ominous warnings, threatening to evict them if they become pregnant.

When the unthinkable happens, the teen hears the echo of those words and tries to postpone the inevitable.

"For adolescents, there's yesterday and today. Tomorrow is not a big concept," said Silverstein. "Their thought is, "If I can get away with this pregnancy for another day, that's one more day I don't have a confrontation.'"

What they don't think about is how the reaction to the pregnancy would very likely be less severe than the reaction to discovering a baby in the closet while rummaging for clothes, as in the Long Island case.

"There's no logic to this," Berrill said. "Just fright and confusion."

But these scared teens are savvy enough to figure out ways to keep their condition under wraps - although it's easier than one might think.

Many teens carry small to start with; today's baggy, multi-layered fashions artfully hide their swollen abdomen, and a low profile keeps them away from scrutiny.

Many of these girls come from families already distracted by other crises. And most parents don't find it unusual for teens to spend a lot of time locked in their rooms or out of the house.

"The average parent sees their adolescent child about as often as a four-leaf clover," Silverstein said.

In 90 percent of pregnancies, a baby will develop with no complications even if the mother doesn't see a doctor.

What's the truly amazing thing is that these young people "have the sense of mind and pain control to perform their own delivery, cut the umbilical cord and deliver the afterbirth," he said.

Once the baby is born, the fantasy of the previous nine months collides with the harsh reality of a crying infant.

"In those moments, there are two choices," Berrill said. "And in a moment of hysteria, dissociation and panic, they can kill the child to continue the denial."

The experts stress that these tragedies stem from a lack of trust and communication.

"My first message is, "Talk to your parents,'" Hilfer said.

"The kids are absolutely convinced their parents are going to kill them. But the parent almost always comes to support and aid the child in her decision-making.

"In the case of the 14-year-old who kept it a secret until her eighth month, she made a terrible decision at a time when she was incapable of handling such a decision. That could have been avoided."

Smart-Smith agrees.

"The bottom line coming from parents has to be, "I love you no matter what.' If your kids believe that, they somehow will come to you, even if they know they'll disappoint you."