SAN FRANCISCO (MarketWatch) — Netflix Inc. shares surged 17% in after-hours trading Wednesday after the online video-streaming company reported fourth-quarter results that topped Wall Street analysts’ estimates, led by strong gains in new subscribers in the U.S.

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Netflix NFLX, -0.05% got a lift after the company reported earnings of $48 million, or 79 cents a share, on $1.18 billion in revenue, compared with a profit of $8 million, or 13 cents a share, on sales of $945 million in the fourth quarter of 2012. Analysts surveyed by FactSet had forecast Netflix to earn 65 cents a share on $1.17 billion in revenue.

A major driver of Netflix’s results was the company’s gains in video-streaming subscribers. Netflix said it added 2.33 million new U.S. video streaming members to end the quarter with 33.4 million such subscribers. Total video-streaming subscribers, including international markets, topped more than 44 million members.

Netflix said it expects new-subscriber momentum to continue in the first quarter of the year, and it forecast adding 2.25 million members in the U.S. and another 1.6 million in overseas markets by the end of the quarter.

The company also said that for its first quarter it expects to report earnings of 78 cents a share. Analysts had forecast Netflix to earn 75 cents a share on $1.24 billion in revenue for the quarter.

In a nod to past changes in pricing plans that led to customer defections, Netflix said that if it does make changes for prices for new members, “existing members would get generous grandfathering of their exiting plans and prices.” For video streaming, Netflix allows members to watch videos on two devices simultaneously for $7.99 a month, and on four devices for $11.99 a month. Netflix said it has been testing out plans for streaming one and three devices.