* Oil prices pare gains
* Tempur Sealy drops on disappointing forecast
* Indexes down: Dow 0.12 pct, S&P 0.23 pct, Nasdaq 0.24 pct (Adds details, comments, updates prices)
By Yashaswini Swamynathan
Sept 28 (Reuters) - U.S. stocks reversed course to trade lower in a choppy market on Wednesday, dragged down by healthcare stocks and as oil prices pared gains.
Bristol-Myers and Amgen weighed the most on the S&P 500 healthcare sector, which fell 0.45 percent. The index had risen 0.7 percent on Tuesday.
Oil prices, which rallied as much as 3 percent earlier in the day, gave up much of those gain as data showed a large build in U.S. gasoline inventories.
Adding to the downbeat market sentiment was the lowering of the 2016 U.S. growth forecast by the International Monetary Fund.
In a testimony before a Congressional committee, Federal Reserve Chair Janet Yellen said the central bank was considering changes to the annual stress tests given to U.S. banks.
Yellen also said the economy was not seeing any meaningful upward pressure on inflation.
"Yellen's remarks are generally in line with expectations. I think what we are seeing today is really a lot of noise," said Terry Sandven, chief equity strategist at U.S. Bank Wealth Management in Minneapolis.
At 11:00 a.m. EDT the Dow Jones industrial average was down 22.77 points, or 0.12 percent, at 18,205.53.
The S&P 500 index was down 5.01 points, or 0.23 percent, at 2,154.92.
The Nasdaq Composite was down 12.81 points, or 0.24 percent, at 5,292.90.
All of the 11 major S&P 500 indexes were trading lower, with telecom services falling the most by 1.28 percent. AT&T was the biggest drag on the index after UBS downgraded the stock to "neutral".
Mattress maker Tempur Sealy's shares plunged 23.2 percent after the company forecast disappointing full-year sales.
Nike dropped nearly 2 percent after the shoemaker's future orders missed analysts' estimates for the third time in a row, attracting a slew of price targets by brokerages.
Advancing issues outnumbered decliners on the NYSE by 1,477 to 1,335. On the Nasdaq, 1,414 issues fell and 1,149 advanced.
The S&P 500 index showed 12 new 52-week highs and two new lows, while the Nasdaq recorded 63 new highs and 22 new lows. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)