Facebook (FB - Get Report) stock was marked lower in pre-market trading Thursday despite the social media icon's topping of Wall Street estimates for its first quarter earnings.

Facebook shares were indicated 1.35% lower at $149.75 each in pre-market trading in New York after falling 2.5 in after-hours trading from a Wednesday closing price of $151.8.

Facebook reported earnings of $1.04 per share, topping estimates of $0.87. Revenue of $8.03 billion - a rise of 49% year-over-year - eclipsed estimates of $7.8 billion. Monthly active users stood at 1.94 billion, also exceeding Wall Street's estimates.

The world's largest social network, however, warned that that expected revenue growth to come down "meaningfully" in the second half, due to a self-imposed limit on the number of ads shown on its newsfeed.

However, the earnings report also came amid a global outage for its WhatsApp messaging system, which is used by more than 1.2 billion people and is a key tool for communications and commerce in many countries.

Facebook said the service, which it acquired in 2014 for $19 billion, was down for "a few hours" before technicians restored it at around midnight London time. 

Earlier on Wednesday, Facebook CEO Mark Zuckerberg said the social network would hire 3,000 more moderators tasked with taking down inappropriate content.

The move comes in response to two incidents in the past month, which saw videos featuring murders in Thailand and Cleveland, Ohio stay on feeds for hours before being removed.

Facebook said it would stop reporting its non-GAAP expenses, income, tax rate or earnings per share, as it moves to include stock given to employees in its public figures.