Wall Street's main indexes opened lower on Wednesday as investors took a breather from a rally that was sparked by the Federal Reserve's likely pivot to a dovish policy, while FedEx tumbled after issuing a grim outlook.

The Dow Jones Industrial Average fell 37.79 points, or 0.10 percent, at the open to 37,520.13.

The S&P 500 opened lower by 3.64 points, or 0.08 percent, at 4,764.73, while the Nasdaq Composite dropped 29.86 points, or 0.20 percent, to 14,973.36 at the opening bell.