U.S. stock index futures added to losses on Thursday after U.S. jobless claims jumped unexpectedly last week to their highest level since October, indicating continued weakness in the labor market.

S&P 500 futures lost 1.7 points and were slightly 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 shed 8 points, and Nasdaq 100 futures fell 2.75 points.

(Reporting by Chuck Mikolajczak)