Several local hospitals are looking for ways to improve security on their obstetrics wards in the wake of the abduction of Jennifer Renee Smith from Arlington Hospital last week, but most agree it is not easy to guard against such an act.

"This kind of incident makes us recognize how vulnerable we are," said Mary Barden, associate nursing director for the obstetrics and neonatal division at George Washington University Hospital. A baby boy was taken from that hospital in 1979 and returned a few days later.

Barden said the constant dilemma on her ward is how to provide security while allowing parents easy access to their newborns. Each nurse in Barden's ward is responsible for about five mothers and their babies. "We try to be vigilant without being militant," she said.

Beginning with a parents' prenatal class that met last evening, Barden said new parents will be instructed that if they do not recognize a hospital employe, they should ask that person to show a picture ID card.

Six of eight local hospitals contacted yesterday said that they require their staff members to wear identification badges with their photographs on them and that parents are reminded to pay careful attention to them. Fairfax Hospital is considering adding pictures to its ID badges.

Employes at Arlington Hospital are required to wear photo ID badges, but apparently the woman who took the Smith baby was not wearing one, according to hospital spokeswoman Elizabeth A. Flynn.

Flynn said that after the infant's disappearance, the maternity ward posted a guard round the clock. That precaution was discontinued yesterday after the child was found.

At Fairfax Hospital, which delivers more babies than any hospital in the Washington area, spokesman Lon Walls said he could not remember a baby snatching.

Walls said that the obstetrics ward is usually full, with as many as 80 mothers and their babies at a time, but that confusion is minimized because the patients are housed in five separate units and new mothers usually deal with only one nurse on each of three shifts.

At Howard University Hospital in the District, where an infant disappeared for 11 days in 1971, nurses on the obstetrics ward are identified by the colors of their uniforms. And at Prince George's Hospital in Cheverly, maternity ward nurses wear colored uniforms instead of the usual white ones. This was "originally done for esthetics, but it has turned out to be a good security measure," said hospital spokeswoman Meg Mullery.

Few hospitals require visitors to sign in and out, but in most obstetrics wards, visitor access to newborns is limited because infants are restricted to the nursery during visiting hours to reduce their exposure to bacteria.

At Greater Southeast Hospital in D.C., access to the maternity ward is restricted to the main elevator; the stairwell to that floor is locked.

And at Columbia Hospital for Women, spokeswoman Annette Lowery explained that if a nurse does not recognize a mother who is asking for her child, the nurse is supposed to check the patient's hospital ID bracelet.

If another family member whom the nurse does not recognize asks for the child, the nurse is required to escort that person and the baby back to the mother's room, Lowery said.

That procedure is taken one step further at Prince George's Hospital.

According to Ronald Weitz, a vice president with the hospital management company, only fathers who can produce photo ID cards bearing the same last name as the child are allowed to take infants out of the nursery.

If a father has a different last name, a nurse must deliver the baby to the mother, Weitz said.