It’s ugly out there, and it could get worse.

Dismal US corporate outlooks and worries about slower worldwide growth have pushed third-quarter earnings estimates into negative territory, which, if it came to pass, would be the first drop in three years.

Third-quarter earnings of Standard & Poor’s 500 companies are now expected to fall 0.1 percent from a year ago, a sharp revision from the July 1 forecast of 3.1 percent growth, Thomson Reuters data showed yesterday.

That would be the first decline in earnings since the third quarter of 2009, the data showed.

The more pessimistic view followed a string of disappointing results and cautious forecasts this week, most notably Apple, the world’s biggest company by market value. United Technologies yesterday cut its full-year profit view to essentially unchanged from 2011’s profit.

That said, the stock market has managed to hold together. The S&P 500 is still up about 8 percent for the year.

Some investors believe the slowing has been factored into stock prices, but the market has also been helped by a steady diet of monetary stimulus from the world’s largest central banks.