F. W. Woolworth Co. said yesterday that its first-quarter profits were 117 percent higher than those for the first three months of 1985, because of the weaker dollar and improved margins.

Meanwhile, Gerber Products Co. yesterday blamed reports of glass in its baby food for a decline of nearly 30 percent in net earnings for its fourth quarter. The company said the glass reports have subsided.

Woolworth said it earned $13 million (20 cents a share) for the three months that ended April 30, up from $6 million (9 cents) in the corresponding 1985 period. Revenue rose to $1.4 billion from $1.2 billion.

*Gerber Products Co. reported net earnings of $12.3 million for the quarter that ended March 31, down 29.3 percent from $17.3 million for the final period a year ago. Earnings per share were down to 60 cents from 85 cents last year, Gerber said.

For the fiscal year, Gerber reported net earnings of $45.5 million, down 19.3 percent from $56.4 million for the previous fiscal year. Per-share earnings were $2.23 compared with $2.77 a year ago.

Fourth-quarter net sales and revenue were $242.7 million, off 2.1 percent from $247.9 million last year, Gerber said. For the fiscal year, the company reported record net sales and revenue of $967.9 million, a 4.1 percent increase over $929.4 million in the previous fiscal year.

The Food and Drug Administration, which tested 50,000 unopened jars of Gerber baby food, reported finding only a few specks of glass.