(REUTERS) -- Stock index futures added to gains on Wednesday after data showed the U.S. economy grew slightly faster than initially thought in the fourth quarter.

S&P 500 futures rose 2.9 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration of the contract. Dow Jones industrial average futures added 11 points and Nasdaq 100 futures advanced 4 points.

(Reporting By Chuck Mikolajczak; editing by Jeffrey Benkoe)