The District of Columbia's infant mortality rate fell in 1982 to its lowest level on record, mainly because of a stunning drop in infant deaths among families living east of the Anacostia River in the poorest part of the city. But the D.C. rate remains among the highest in the country.

The city's rate of deaths of babies less than a year old was 20.3 per thousand live births in 1982, down from 22.6 in 1981, Mayor Marion Barry announced yesterday.

This figure compares with a national average of 11.2 per thousand, according to the National Center for Health Statistics.

The most dramatic change took place in Ward 8, which lies east of the Anacostia River and is the city's poorest ward. There, the rate plunged from 22.5 per thousand in 1981 to 13.7 per thousand in 1982, giving it the second-lowest rate among the District's eight wards, according to statistics from the D.C. Department of Human Services.

City officials could not immediately explain the sharp improvement, but some familiar with the field said one possibility was increased efforts for maternity and child care in that area by Hadley Memorial Hospital.

Others attributed the overall decline to increased public awareness of the problem, better nutrition programs, counseling and education.

"It is even more dramatic at a time when other major urban centers are having an increase, that we are having a decrease," said Dr. Frederick Green of Children's Hospital.

Detroit, Baltimore, Newark and other large cities recently have experienced increases in their infant mortality rates because of economic problems there, he said.

Washington experienced increases in the infant death rate in Ward 6, from 22.1 to 25.3 per thousand, and in Ward 5, from 28.7 to 32.3 per thousand, highest of any city ward. Ward 3, encompassing an affluent area of Northwest, had the lowest rate by far at 2.8 per thousand.

When Barry entered office in 1979, the city's infant death rate was running at 25.8 per thousand and the new mayor declared this the city's "number one health problem." He told the health department to come up quickly with a plan to attack the problem and later appointed a blue-ribbon panel of experts to develop ways of reducing infant deaths.

The panel, headed by Dr. Green of Children's Hospital, came up with a 49-point plan, including improvements at city hospitals, better transportation of mothers and sick infants, and training in infant resuscitation by nursury personnel.

More than half of the suggestions have been implemented in some form, though others were too expensive, given the city's financial problems, he said. One of the most significant achievements occurred only a few months ago with an agreement by city hospitals, after years of resistance, to let outside experts evaluate their nurseries and the kind and quality of care they provide, Green said.

The infant mortality rate went down in 1979, the first year of Barry's first term as mayor. It went up in 1980, but declined again in 1981.

Barry yesterday announced two new programs aimed at preventive care and counseling of expectant mothers to be started soon in the city. Infant deaths are closely related to low-weight births, and many experts believe better nutrition and health care for the mother will reduce the number of infant deaths.

One program, to be run by the Greater Washington Research Center with private grants, will focus on one geographical area with many high-risk mothers and will provide them with prenatal medical care, nutrition supplements and counseling on care for themselves and their infants.

The three-year pilot project, to be funded in initial stages by the Ford Foundation, will be monitored by the National Institute of Child Health and Human Development and may become a model for the rest of the country.

Barry also announced that he has asked school officials to develop plans for more family-planning training and education for junior high school students. "We need to get them thinking about their own sexual habits," he said.

Nationwide, infant mortality rates have declined from 20 per thousand in 1970 to 11.2 last year, but the rate for blacks is much higher than for whites.

In the District, there were 7,710 live births among blacks in 1982 and 180 infant deaths for a mortality rate of 23.3 per thousand. For whites, the number of births was 1,668, with 10 deaths, for a rate of 6.0 per thousand.