Stock index futures fell on Thursday as traders cited a statement by the president of the European Central Bank expressing caution over more bond purchases to ease the region's debt crisis.

S&P 500 futures fell 10.4 points and were 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 85 points, and Nasdaq 100 futures lost 14.5 points.

(Editing by Jeffrey Benkoe)