The number of abortions performed in the District of Columbia declined 5.3 percent last year, continuing a seven-year downward trend, the D.C. Department of Human Services reports.

For the first time in that period, however, more than half, 50.8 percent, of all abortions performed in the city were done on District residents. The gradual shift apparently results from the increasing availability of abortions in suburban hospitals and clinics.

According to an annual statistical report, there were 27,183 abortions performed in the District in 1980, 13,809 of them on District residents.. In the prior year, there were 28,694 abortions, 13,611 on District residents.

For several years, the number of abortions performed on city residents has exceeded the number of live births to mothers residing in the District. Last year, for example, there were 9,257 births, compared with 9,403 in 1979.

The report did not show how many of the abortions were paid for by public Medicaid funds. Those statistics are kept on a fiscal rather than calendar year basis.

In 1973, 40,812 abortions were performed in the city, including 10,019, slightly fewer than a quarter of them, on District residents. The total dropped to 33,010 in 1974 and fell below 30,000, to 29,545, by 1977. The proportion performed on District residents has consistently declined although in actual numbers the total has risen slightly year by year.

Other statistics: Of the 1980 abortions, 32 percent were performed on Maryland residents and 13.3 percent on Virginians. There were 386 abortions on girls under 15, or 1.4 percent of the total. Women over 40 accounted for 334, or 1.2 percent. Of those who had the procedure done, 18,049 (66.4 percent) had never married; 5,051 (18.6 percent) were currently married and 2,888 (10.6 percent) were widowed, divorced or separated. The status of the other 1,195 was unreported. Racially, 55.5 percent were black and 34.8 percent were white, with the balance listed as other races or unknown.