Facebook Inc's first-quarter revenue climbed 45 percent to just over $1 billion (619 million pounds) as daily active users leapt 41 percent, the world's largest social network disclosed ahead of its landmark initial public offering.

Facebook added more than 1,000 employees in the year ended in March, taking its headcount to 3,539, it said in an updated filing with the U.S. Securities and Exchange Commission.

Revenue grew to $1.058 billion from $731 million in the year-ago quarter. Average monthly active users increased to 901 million as of March 31, 2012, from 680 million a year ago.

Net income fell to $205 million from $233 million over the same period, according to the filing.

Facebook is preparing for an IPO that could value it at up to $100 billion and could come as early as May.

(Reporting By Alistair Barr and Alexei Oreskovic; Editing by Gary Hill and Richard Chang)