BDM International Inc., a McLean technical services firm, reported first-quarter profits of $2.9 million (28 cents a share), a 34 percent increase from the $2.1 million (21 cents) the company earned in the first quarter of 1985.

The company said revenue increased 39 percent, to $70.7 million from $50.8 million.

Earle C. Williams, president of BDM, told securities analysts yesterday that new contract awards were $64 million -- substantially below the new government orders during the first quarter of last year. But Williams said the level of the 1985 new contracts was elevated because BDM received its biggest award ever in that quarter -- a 10-year contract to develop a data base for the Air Force.

*USF&G Corp., an insurance company based in Baltimore, reported first-quarter profits of $143.6 million ($2.23) compared with a loss of $29.1 million during the first three months of 1985. The profits included a $50.2 million gain on investments and a $42.8 million tax credit.

Operating earnings were $50.5 million compared with an operating loss of $52.3 million a year ago. That loss was moderated by a $28.2 million gain on investments.

*Genex Corp. of Gaithersburg reported that selling some land at its headquarters enabled it to cut its first-quarter loss to $194,000 (2 cents a share) from $2.5 million (19 cents) the year before. Revenue decreased to $930,000 from $4.8 million.

The biotechnology company said the smaller net loss partly reflected the sale in March of surplus land adjacent to the company's facility.

The dramatic drop in sales reflects the decision of G. D. Searle & Co. to stop buying Genex's L-phenylalanine, an amino-acid ingredient in aspartame. Searle's $4.2 million in purchases was 88 percent of 1985 first-quarter revenue.

Since then, Genex has worked to increase its revenue from biotech research contracts and sales of its enzyme-based drain cleaner.