Netflix Inc, the top video rental company, reported second-quarter revenue that fell short of expectations and cautioned that subscriber growth would slow in the third quarter, sending shares down about 9 percent.

The company said quarterly earnings rose to $68 million, or $1.26 a share, from $38 million, or 70 cents a share, in the period a year ago.

Revenue rose 52 percent to $788.6 million, but fell short of the average analyst estimate of $791.5 million, according to Thomson Reuters I/B/E/S.

It also cautioned that it would add fewer U.S. subscribers in the third quarter than it did in the period in 2010, worrying investors about slowing growth and weighing on its share price in late trade.