American Security Corp., the parent of American Security Bank, reported its first-quarter net income rose 17.8 percent, from $5.8 million (50 cents a share) in the 1985 first quarter to $6.8 million (57 cents).

Meanwhile, First American Bank of Maryland and Federal National Mortgage Association reported higher quarterly earnings.

American Security Corp. said the company's earnings performance reflected strong core deposit growth, loan growth, increases in net interest revenue and strong growth in noninterest income.

Loans averaged $130 million more in the first quarter of 1985, with the growth concentrated in domestic construction and commercial loans, the company said. At the end of the first quarter on March 31, loans stood at $2.19 billion, compared with $2.06 billion at the same point a year ago.

Nonperforming loans decreased about 50 percent during the quarter, from $126 million in last year's first quarter to $66 million this year, the bank holding company said.

As of March 31, the company's assets totaled $4.16 billion, compared with $3.63 billion a year ago.

*First American Bank of Maryland announced that net income grew 20.4 percent during the first quarter of 1986, from $1.07 million ($1.08 a share) in the first quarter of 1985 to $1.29 million ($1.04) this year. The bank attributed the improved earnings to an overall 30.7 percent increase in average earning assets.

As of March 31, total assets were $695.1 million, up 27.5 percent from the $545.2 million reported at the end of the first quarter of 1985. Loans totaled $462.2 million, a 30 percent increase over $355.5 million the year before.

*The Federal National Mortgage Association moved into the black in the 1986 first quarter, showing profits of $34.7 million (47 cents a share), compared with a loss of $17.4 million (26 cents) in the same period a year ago.

David O. Maxwell, Fannie Mae's chairman and chief executive officer, said the improved earnings reflected a restructuring program designed to make the company less sensitive to fluctuations in interest rates.

During the first quarter that ended March 1986, Fannie Mae charged off $41.8 million in for losses on conventional single-family loans, down from $51.4 million in the 1985 fourth quarter.