Women's National Bank of Washington reported yesterday a small operating profit for the month of December and a loss of $76,000 for its initial seven and one-half months as the nation's first federally chartered women's bank.

Many new banks take up to 24 months in business before showing profitability on a month-to-month basis and Women's National President Emily Womach forecast that 1979 will produce enough earnings to overcome the initial operating losses.

Metropolitan Federal Savings and Loan Association, of Bethesda, mean-while reported record profits for its business in 1978. The S&L, with yearend assets of $244 million, is one of the nation's largest financial institutions headed by a woman -- President Jessie Hilderbrand.

At Women's National, which opened at 1624 K St. NW last May 15, December business produced profits of $2,472. "Our growth has been more than we ever expected," said Womach, detailing the 1978 results: Deposits doubled in the six months to $4.66 million on Dec. 31, assets jumped 73 percent to $7 million and the bank opened more than 2,600 accounts -- surpassing projections for the end of this year.

Scientific Time Sharing Corp., a Bethesda computer services firm, reported higher revenues but lower profits in the quarter and six months ended Nov. 30. Chairman Daniel Dyer said the lower earnings reflect exhaustion of investment tax credits which resulted in higher income taxes.

For the six months, earnings dipped to $425,000 (28 cents a share) from $519,000 (35 cents) in the 1977 period as revenues jumped 24 percent to $7.7 million. Operating profits before taxes were up 16 percent, Dyer noted.

In this recent quarter, the company earned $212,000 (14 cents) vs. $274,000 (19 cents) and sales rose 23 percent to $4 million.