A sudden increase in the number of children who have been repeatedly abused and neglected has been recorded at Children's Hospital, according to a new study by the hospital's division of child protection.

The study identified 36 instances in which abused children who had been treated at the hospital were reinjured, or their siblings abused, between January 1981 and June 1982. Two of the children died.

Despite the increase from 2 percent to 5 percent in the number of repeatedly abused children, the recidivism rate for child-abuse cases treated at Children's Hospital is substantially lower than the national average, statistics show.

According to a 1979 study done for the National Center on Child Abuse and Neglect, 13 percent of abused children suffered subsequent abuse that was reported to authorities within the same year.

Fewer than one-third of the families in which repeat abuse occurred received follow-up counseling services from the hospital, according to the study. "Children's Hospital is a voluntary agency and families can choose whether to deal with it or not," said Mary L. Holman, the study's author.

Holman, who retired last week as clinical coordinator of the child protection division, said that before 1980 the problem of recidivism was so rare at Children's Hospital that it was not tabulated. In 1981, however, there was a sudden increase.

She speculated that the increase was caused by a change in the District's child welfare policy, which now discourages the city from removing children from their homes. Formerly, abused youngsters were often sent to a series of foster homes throughout their childhood.

Although the practice "spared children from further abuse and neglect," Holman's study noted, "many sustain emotional damage from lack of family stability."

But according to Regina Bernard, director of the District's Child and Family Services Division, other factors, such as the recent poor economic situation, play a larger role in repeated abuse than any change in the division's policies.

Bernard said a 1981 report by the D.C. auditor that was critical of foster care did result in the city providing more services to abused children in their homes.

But she noted, "Providing permanency for our children does not mean we're leaving children in their home to be abused or neglected."

The families responsible for the repeat abuse and neglect included one psychotic parent, two alcohol abusers, two drug abusers, one 14-year-old mother and one adult who had been previously convicted of homicide, the hospital study said.

The ways in which the children had been abused ranged from poisoning and malnutrition to burns and beatings.

The study also found that:

* Most of the repeated abuse or neglect occurs within six months of the initial incident.

* In repeat cases, face injuries and bone fractures were the most frequent injuries and in one-third of the cases, the severity of the injury increased after the first incident.

* Almost twice as many mothers as fathers were identified as responsible for the abuse.

* Most of the children were under 3 years of age.

Holman conducted the study in part to fulfill the requirements of a federal grant Children's Hospital received from the National Center on Child Abuse and Neglect. "By showing a pattern of recidivism, perhaps state laws will begin to allow judges to remove children permanently in repeat cases," she said. "I feel one relapse is enough."