The nation's economy grew at a sluggish 2 percent in the fourth quarter of 1988 stunted by drought losses and red ink on the trade balance sheet, the Commerce Department said Tuesday.

The estimate for the nation's gross national product, the total output of goods and services, was the department's second for the final quarter of 1988 and unchanged from the advance estimate issued last month.GNP grew more slowly in every successive quarter last year, starting 1988 up 3.4 percent in the first quarter, up 3 percent in the second, up 2.5 percent and up 2 percent in the final quarter.

Total GNP, after adjustments for price changes and seasonal variations, totaled $4.03 trillion at an annual rate in the fourth quarter, the bureau said.

The department's Census Bureau said the summer's drought was largely to blame for slowing economic growth, slicing 1.1 percent off GNP in the fourth quarter alone.

The recovery from the drought will show up in statistics for economic growth beginning in the first quarter of this year, and the bureau estimates that will add 2.5 percent to GNP growth when the first 1989 numbers are released in April.

The stubbornly high trade deficit also reduced fourth quarter GNP more than previously estimated, the bureau said.

Real net exports dropped $9.4 billion in the fourth quarter, after a decrease of $1.3 billion in the third, the bureau said. That was the worst de-terioration of the trade account since the third quarter of 1986, when real net exports dropped $11.6 billion, the bureau said.

Inflation as measured by the GNP fixed weight price index grew 4.2 percent in the fourth quarter, less rapidly than the 5.3 percent increase in the third quarter, the bureau said.

However, the bureau's implicit price deflator, another measure of inflation that includes the composition of GNP as well as price changes, was higher in the fourth quarter, 5.3 percent, up from 4.7 percent in the third quarter of 1988.