Law enforcement officials still have no leads in the recent abductions of two infants from Maryland hospitals, the third and fourth such incidents involving residents of the Washington-Baltimore area since last year.

The abductions have highlighted security measures in many local hospitals. Measures range from no security provisions at all to 38 closed-circuit video cameras and security guards at Johns Hopkins Hospital, from which 2-day-old Kendall B. Kernes was taken on Thursday.

Jeremiah Thate, now 4 weeks old, was abducted from Prince George's Hospital Center last week. Law enforcement officials said the two cases appear to be unrelated.

"Two in one week nationally is rare," said Andy Manning, a spokesman for the FBI in Maryland. "The cases are very tough. We have not come up with anything."

"Unfortunately, we have seen a tremendous increase in these incidents," said James Scutt, a former police officer and currently a technical adviser to the National Center for Missing and Exploited Children in Washington. "And we don't know how many have gone unreported."

While baby snatchings have prompted extra security measures on many obstetrics units, most area hospitals have not instituted new building-wide changes because such incidents are rare.

At Children's Hospital in Washington a guard stationed at a desk by the elevators leading to patients' rooms, usually stops only individuals who look suspicious or are in the building after visiting hours, a hospital official said.

Access to nonmaternity wards may be easier. Jeremiah Thate, for example, was not in a supervised nursery. He was alone in a room in the pediatric unit when he was abducted, officials said.

Last July, a Bradbury Heights woman posing as a nurse abducted a 3-day-old boy from Arlington Hospital. Valerie Holbert, 22, was tried and found not guilty by reason of insanity and was ordered to undergo psychiatric therapy.

In November, Phillip Worthington was taken from his mother's arms in a Sellersville, Pa., hospital by an Ellicott City woman posing as a nurse. Ramona Jean Thompson, 44, pleaded guilty in February to kidnaping charges and was sentenced to 18 years in prison and ordered to undergo psychiatric evaluation.

Although some local hospitals said they increased security in the wake of the widely publicized Arlington Hospital kidnaping last year, many others still do not monitor visitors leaving the premises or require name tags on infants.

An informal telephone survey of eight local hospitals yesterday found that while several ask visitors to sign in when they enter the hospital, none strictly monitors people leaving the building. However, most facilities do expect nurses and security employes to be particularly vigilant on the obstetrics units.

At Columbia Hospital for Women in the District, mothers are urged not to keep their babies in their rooms with them around the clock, but rather to place them in the nursery before the mothers shower or nap.

At Fairfax Hospital, where more than 7,000 babies are delivered each year, "security is being stepped up" this week, according to spokesman Lon Walls. He would not give details, but pointed out that all hospital employes are required to wear photo identification badges at all times.

Law enforcement officials, psychologists and psychiatrists can explain why abductions occur, based on the histories of people who have been arrested and charged in such cases. But they are at a loss to explain the rash of recent incidents.

"Crimes occur in spurts," said the FBI's Manning. "Two years ago we charged more spies than we had in the previous 15 years. It can very well be that {the infant abductions} are copycat crimes. These are very high-profile crimes that get a lot of media attention."

"Historically," said Scutt of the National Center for Missing and Exploited Children, "within six months before the incident, the abductor has lost a child or has been told that she cannot have children."

In 1986, the FBI investigated 29 kidnapings in which the victim was taken across state lines. The victims in all 29 cases were 6 years old or younger. The National Center for Missing and Exploited Children has recorded 10 abductions from hospitals in the past 2 1/2 years.

Dr. David Goldstein, an associate professor of clinical psychiatry at Georgetown University Medical School, said that the people who take children from hospitals generally "can't stand the sense of loss."

"That frequently has to do with whether the person has had a sense of loss in childhood, such as the death of a mother. With an incident such as that, they become more susceptible to loss as an adult. To such a person, I would think that the loss of the capacity to have children or the loss of a child would be so devastating that they are driven to make up for the loss."

Health professionals and law enforcement officals are not sure why abductions are occurring more frequently. They said one possibility is that the system for recording such incidents is better now than in the past. They also cite the scarcity of infants available for adoption.

"That's a question that no one can pin down," said Scutt.

Staff writer Chris Georges contributed to this report.