Facebook on Wednesday said that its revenue grew 49 percent in the fourth quarter, helped by the company's strong mobile advertising platform. The company said it ended 2014 with 1.39 billion monthly users, with 86 percent of them accessing its service on smartphones and other mobile devices.

Mobile ads accounted for 69 percent of advertising revenue in the fourth quarter, or $2.48 billion.

Facebook's fourth-quarter overall revenue grew at a slow rate, to $3.85 billion.

Revenue for the full year 2014 was $12.47 billion, an increase of 58% year-over-year.