Many of Washington's children in the preteen and early teen-age years have consistently active sex lives and the amount of sexual activity may be increasing, according to city records and health and social services workers.

It is difficult, the experts caution, to detect trends and make comparisons, because statistics are sometimes indirect and occasionally inconclusive. In most respects, the experts say, children's sexual activity in Washington seems to mirror that of children in other parts of the nation.

Still, city records on abortions, births, veneral diseases and the use of contraceptives, as well as interviews with doctors, social service officials, educators and family-planning advocates, indicate frequent sexual activity among the city's youngsters. The records show:

Between 1977 and 1980, nearly 200 14-year-olds in Washington had babies. Fourteen of them were giving birth to their second child.

In 1980, the number of children per 100,000 in the 14-or-younger age bracket who were treated for gonorrhea was six times higher in Washington than in the nation as a whole. The number of adults per 100,000 treated for gonorrhea was also six times higher in Washington than in the nation as a whole.

In 1979, the last year for which statistics are available, 400 abortions were performed on girls 14 or younger.

"I think we have seen recently an increase [in early teen-age sex] and younger ages -- as young as 10," said Alicia Fairley, acting chief of social services in the D.C. Department of Human Services (DHS). "We see that increasing. It's not dramatic, but it's significant enough to cause concerns."

"Twelve used to be a pretty good cut-off age [as the youngest age of sexual activity], she said. "But now we're seeing it drop."

Marie Garner, a social worker in the Pediatrics Department at D.C. General Hospital, said she is not certain whether the phenomenon of sexual activity among younger children is new or just now receiving public attention. She said the youngest sexually active patient she remembered was a 9-year-old girl made pregnant by her 15-year-old boyfriend.

Marilyn Bowie, executive director of the D.C. Interagency Council on Family Planning, said, "We seem to have more young people engaging in sexual activity between girls and boys at an earlier age."

Based on recent studies, she said, "There is no reason whatsoever to think that Washington would be radically different from the nation as a whole."

The D.C. City Council is expected to take final action Tuesday on a comprehensive package of changes in the city's sexual assault laws. Among the provisions initially proposed by council member David A. Clarke (D-Ward 1), was one that would have changed the city's laws on statutory rape.

The bill would have allowed consentual sex for children in the 12-to-16-year age bracket with other persons within four years of their age and for children under 12 with persons within two years of their age. The measure was withdrawn after strong objections by ministers and others.

Clarke said the proposed measure was not intended to condone or encourage sexual activity among teenagers. "We never examined how much children were doing it because we never intended to legislate according to what children were doing," he said last week.

One indicator of sexual activity is the number of births to young mothers. Most of the children born to teenaged mothers are born to persons 15 years or older, both in Washington and throughout the nation. However, an average of 71 girls age 14 or younger have babies in Washington each year. Most of the mothers are city residents.

From 1977 to 1980, there were 61 births to 13-year-olds, two of whom had their second child. During the same three-year period, four 12-year-olds and two girls 11 or younger also had children.

Another indicator is the number of abortions, although these figures are sometimes inconclusive. Reporting is voluntary, and the most recent data, from 1979, is not fully broken down by age and place of residence. However, there are indications that more than half the abortions performed were on nonresidents.

Nevertheless, in 1979, 401 reported abortions in the District were performed on girls 14 and younger. That is more than the 289 abortions reported performed on girls 14 and younger in 1977. But again, there is no indication of how many of those girls were city residents.

The younger the child, the more likely she is to have a delayed abortion, according to a newly published national study of teen-age sexuality and pregnancy done by the Alan Guttmacher Institute, a New York City-based research and analysis organization. Two-thirds of the girls under 15 wait until after the eighth week of pregnancy, and another 14 percent wait until after the 16th week, the study found. Abortions that late are 13 percent more dangerous than those performed earlier.

Jane Quinn, project director at the Center for Population Options, remembers from her seven years as a counselor in DHS that among pregnant youngsters, those in the elementary-school age group were among the most difficult to help.

"Often they would come in wanting an abortion, and they couldn't have one because they were six months pregnant," she said.

She said she saw "probably one a year who were in the fifth or sixth grade. You remember those kids because they have so many problems and their situations are so poignant."

Another index of youthful sexual activity is teen-age use of birth control. Mary Janney, executive director of Planned Parenthood of Metropolitan Washington, reports that more teen-agers seem to be requesting contraceptives from clinics run by her agency, one of many in the District.

Last year Planned Parenthood served 108 adolescents age 14 or younger, and 4,220 older teen-agers.

Still another indicator is veneral disease, and in this area the District is distinctly different from the nation as a whole. Figures from the U.S. Centers for Disease Control in Atlanta show, for example, that in 1980, there were 11,256 reported cases of gonorrhea nationwide among children 14 or younger, or 21.6 per 100,000 population.

The same year, the District had 180 cases for the same age group, or 134.3 per 100,000 population -- more than six times the national rate. The rate for all age groups is also more than six time higher in the District than in the nation as a whole.

Again, District officials urged caution in looking at the statistics. "You can have increases [in the incidence of VD] because of increased activity or because of increased exposure," John Heath of the DHS venereal disease control program said. He noted that the figures also are based on reported cases, a reflection of treatment and the quality of venereal disease-control services.

Sexual activity that does not result in pregnancy, disease or request for contraceptives is more difficult to measure. It is best gauged by the observations and experiences of those who treat or counsel children and young adults.

Dr. Anita Robinson, director of the year-old Adolescent Pediatrics Department at D.C. General Hospital, has found that about a third of the 1,000 outpatients seen in her department this past year were there for sex-related problems, including a few persons as young as 10.

Seventy-five percent indicated on a first-visit questionnaire that they were sexually active, and about 25 percent "have venereal disease, which indicates sex activity," Robinson said.

Dr. Artist Parker, gynecologist at East of the River Health Center, said, "I don't see very many 10-year-olds, but quite a few 12s. It's beginning to drop." She said children as young as 11 and occasionally 10 are referred to her for sex-related problems.

Dr. Thomas J. Silber, head of adolescent pediatrics at Children's Hospital, said the "age at which sex starts is going down more and more." About 10 percent of the patients seen in his department are treated for sex-related problems, he said.

Bowie said her assertion that Washington probably is similar to the rest of the country is based on examination of the study done by the Alan Guttmacher Institute.

Nationally, the study found, 12 million -- about 40 percent -- of the 29 million Americans 13 to 19 years of age have had sexual intercourse. Among 13- and 14-year-olds, 18 percent of the boys have had intercourse and 6 percent of the girls, the study found.

The average age at which women first have sexual intercourse -- 16.4 for whites and 15.5 for blacks -- remained fairly constant during the 1970s, according to the study. But the total number of teen-agers having sexual intercourse nearly doubled -- to 46 percent -- among whites, while the rate among black teen-agers rose only slightly.

Although the District compares poorly with other cities in regard to some problems related to youthful sexuality, it compares well in regard to the response to these problems, many experts said.

A number of organizations, research projects and resource outlets are working on these problems, they said.

"I think we're pretty good compared to other metropolitan areas," Janney said.