* Aetna lifts outlook
* Procter & Gamble tweaks forecast
* First-quarter GDP data on tap
* Futures down: Dow 11 pts, S&P 1.2 pts Nasdaq 3.75 pts
By Edward Krudy
NEW YORK, April 28 (Reuters) - U.S. stock index futures edged lower on Thursday, a day after the Nasdaq rose to a 10-year high and investors looked ahead to first-quarter growth data amid concerns the U.S. economy may be starting to slow.
* Economists in a Reuters survey forecast a 2.0 percent annualized pace of growth, compared with 3.1 percent in the fourth quarter, but rising commodity prices have left some worrying about a deeper slowdown.
* The prospect of continued low interest rates after Fed Reserve Chairman Ben Bernanke's first-ever press conference drove stocks Wednesday and helped to cement a bullish stocks outlook, even as the seasonally weak month of May approaches.
* "The 'sell in May and go away' is not likely to happen this year," said Peter Cardillo, chief market economist at Avalon Partners, referring to an old stock market adage.
But he added, "obviously the market is at high levels here and any negative news could take some of the starch out of the market," noting that a GDP reading under 1.5 percent would be a blow for investors.
* A number of companies reported earnings, but the market impact was slight ahead of the GDP data. Aetna Inc raised its full-year profit forecast, continuing a string of strong results for the health insurance industry. The shares rose 5.5 percent to $42 in premarket trading.
* Procter & Gamble Co lowered the high end of its profit forecast as it tries to trim expenses and increase prices to offset rising costs for materials.
* S&P 500 futures fell 1.2 points and were just below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures dropped 11 points, and Nasdaq 100 futures lost 3.75 points.
* U.S. crude futures rose to their highest in 2-1/2 years and metal prices rallied as the Fed appeared in no rush to tighten monetary policy.
* The dollar sank to a three-year low against a basket of currencies and was at risk of a drop to $1.50 versus the euro, with momentum-driven investors anticipating that U.S. interest rates will be low for a long time.
* Japan's Nikkei closed up 1.6 percent while European stocks edged 0.1 percent higher in morning trade, gaining ground for the sixth straight session after strong earnings from Deutsche Bank and Royal Dutch Shell.
* Starbucks Corp warned Wednesday that rising costs will take a bigger chunk out of earnings than previously anticipated, and its full-year forecast disappointed Wall Street.