The women's nine-year-old son was the first to notice the curious hospital ID bracelet on his brand-new baby sister's left wrist.

"Why is the baby wearing this?" the boy asked his father as they peered down into the crib to examine it.

On the bracelet was the name of another child.

At that moment, his mother was in bed upstairs, exhausted, yet relieved to be back home in their brick split-level in Silver Spring. She had an easy pregnancy, working right up to the end in her job as a government program analyst. It would be her fourth child, her last; she was reflecting "how neat" it would be to have another baby around the house.

But an apparent administrative foul-up at George Washington University Hospital was about to turn the joy of childbirth into a nightmare. And she would come face-to-face with the secret fear of many new mothers: that somehow she might go home with the wrong child.

"Did I doubt this was my baby? Yes," said the mother. "I kept generating worst-case scenarios. I kept asking myself, 'Is this the right kid?'"

"The dimension of the problem suddenly dawned on me -- I was horrified," said the father, a Washington political consultant.

The parents, who agreed to be interviewed if the names were not used, phoned Andrew Duncan assistant administrator of GW Hospital, with the news. It was April 1. He later said he thought "someone was pulling an April Fool's joke." Then he sensed the anxiety in the voices; the parents were insistent that something be done right away. He told them to bring the baby back that night for an identification check -- and called the FBI for help.

It was about 10 p.m. when the parents, clutching a birth certificate with the child's vital statistics -- blood type, footprints, name -- and their seven-pound, brown-haired baby girl, huddled with two FBI fingerprint examiners, Duncan and other hospital officials inside a GW conference room downtown. To compound the confusion, the baby was wearing two additional ID bracelets with the correct, name, one on the right wrist, the other on the ankle.

The examiners pored over the birth certificate and tried to compare the tiny swirls and ridges peculair to each newborn with the hospital's footprint records; but GW's copy was "too smudged," said one FBI official. The examiners took new footprints on the spot, which they said they would magnify later at headquarters.

"Are you sure you'll be able to tell?" asked the anxious father.

The technician reassured him. "I was involved in the Guyana ID Project," he said, referring to the Jonestown mass suicide. "I've had a lot of experience identifying babies' prints."

On the table were two sets of birth records: the baby's and the other child's. Their baby screamed as the nurse drew a blood sample and the anxious parents fretted as they waited for the results to come down from the lab.

It was A-positive, they were told, the same blood type on the child's birth certificate. The other baby had O-positive blood. The father said he was told then that it would be impossible for him to conceive an O-positive baby and that meant they had the right child.

"But I still had doubts," he said. "From high school biology, I remembered a blood test can't prove you're the father, only that you are NOT the father."

The next day, the FBI phoned them at home with good news: the footprints matched the prints on the birth certificate. The baby was their baby.

But the episode still haunts them.

The parents still don't know how the wrong bracelet wound up on their child's wrist. Nor does the hospital.

"It looks like we made the mistake of not properly checking the [identification] bands before the discharge," says Duncan, who dismisses the incident as so "minor, it's hardly worth mention in a cocktail party conversation. After we looked at the charts, there was no doubt in our minds they had the right baby."

Otherwise, the incident would have been nearly identical to an actual baby swap that took place at GW five years ago when Stanley Porter nearly lived out the rest of his life as Lonnie W. Sharpe III -- and vice versa. In that case, a maternity ward nurse apparently failed to check the name bracelets and handed over two infants to the wrong mothers. An observant grandmother caught the mistake the same day.

"The feelings are still raw," said the mother, who blames her problems producing breast milk for the baby on the stress from the incident.

But GW discounts her theory. "Stress or worry can't dry up a woman's milk supply if everything is cleared up within a reasonable time," said Dr. Benny Waxman, a GW Hospital obstetrician. "It's not like a kidnaping where there is a total separation of the mother from the baby."

Dr. Mary Ann Fletcher, associate direction of GW's newborn nursery and pediatrician of the other baby, scoffs at the notion that the mother couldn't identify her child. "Once a family has seen their child, they can never mistake it for another," she said. "If I were the mother, I'd be embarrased to admit" that possibility.

When a baby is born at GW, a band with the mother's name and the baby's blood type is immediately placed on the right wrist and an ankle. Before the baby leaves the hospital, the bracelet, must be compared to the mother's bracelet and surrendered, as at a hat check stand. In this case, one baby sent home with three bands, the other with none.

Even seven weeks later, the parents remain bitter. "I feel as if a joyous experience was taken from me," said the mother. "I feel cheated."

The hospital never told the other famly what happened. "Why upset another set of parents unnecessarily?" asked Waxman, chief of obstetrics at GW.

But the family found out anyway. In a final ironic twist, the mother bumped into the "other mother" while returning a baby gift at Lord & Taylor's last week. She heard the mother say the baby was six weeks old and that the baby had been born at GW the day before her child.

"Did your baby go home with an ID bracelet?" she interrupted.

"No, but how did you know that?"

Well, it's a long story . . .