Peggy Humphreys sat in an armchair holding Casey Elizabeth, her day-old daughter, surrounded by her husband David, her mother-in-law Josephine, and sons Douglas, 6, Justin 3, and Brian, 14 months.

"When Brian was born, Justin was very, very jealous," she said. "Right now, Brian doesn't even know what's happening. Brian, look at the baby," she commanded for the benefit of a photographer. "Look at the baby, Brian! Brian! She's your new sister. You're supposed to be checking her out."

The family tableau was not arranged in the Humphreys' living room, despite the presence of children younger than 12 years of age. Rather, part of the Humphrey clan was gathered in a newly decorated family room in the Georgetown University Medical Center's obstetrical unit.

For Georgetown, like more than half a dozen other hospitals in the Washington area and a growing number around the country, has begun allowing visits to the OB unit for young children who in times past were left home to wonder where Mommy was and what she was doing during the days before she returned home with a new brother or sister.

The program at Georgetown is unusual because it is the only such program in the area allowing the newborn and brothers and sisters in the same room.Other hospitals allow the brothers and sisters to view the new member of the family through the nursery windown and tend to have mother and older children visit at the window or in a day room of some sort.

Among the other area hospitals that have such visitation programs or are planning them are the Washington Hospital Center, Arlington Hospital, Columbia Hospital for Women, Fairfax Hospital and Sibley Hospital.

The reasons most often given for instituting the window-shopping form of sibling visitation are the fear that the older children will carry infections to the newborn and the thought that allowing children in the mother's room will prove an inconvenience to other patients on the floor.

Georgetown has eliminated the latter problem by turning the first room of the unit into a visiting room. Mother and new baby are brought to the room which is the first a person comes to when he enters the obstetrics unit, where the family can meet in something approaching home-like comfort.

The problem of potential infection has been handled by having the parents produce proof that the older children have been immunized against the usual list of childhood diseases. The parents are also asked if the child currently has a fever, cough, runny nose or congestion, rash, diarrhea, vomiting or any other health problem.

"We're hoping this will influence how children view the hospital," said Kathy Beard, a nurse-coordinator who was involved in the establishment of the program. "If they come on a happy occasion, then they'll feel better about" hospitals in general.

Dr. Bennett Olshaker, a Washington psychiatrist who for many years specialized in child psychiatry and who is the author of two books on child rearing, sees sibling visitation as beneficial to the children at home.

"It's a good idea for several reason: One, young children sometimes don't understand where their mother went and what happened, so it would be beneficial for them to see. . .

"The other thing," said Olshaker, "is some times can be much more devastating for a young child than people think."

Children may seem resentful . . . may seem upset, but on balance it's better that they see the mother and try to understand what's happened," Olshaker said.

"I think this is a big help in letting the other children adjust," said Peggy Humphreys. "They've been looking forward to it."

"Justin was very surprised to find out she (the baby) didn't have any teeth," said David Humphrey's a medical malpractice attorney.

Humphreys remembered that when Brian was born the other children had waited outside the hospital, playing on a patio, while he visited his wife. "I went to the window and waved," he said.

"I think this (the visitation) would have been a big help if Justin could have come in when I'd had Brian," said Peggy Humphreys. "You leave them in the middle of the night . . ."

Douglas woke up in the middle of the night and wanted his mom," interjected Humphreys.

"I did?" the 6-year-old asked quizically.

When the children first arrived at the hospital, said Peggy Humphreys. Justin "asked why I had my 'jamas' on. He told me to get dressed and come home."