In its first earnings report as a public company, Lyft's(NASDAQ:LYFT) top-line growth continued to surge as it builds its active-rider base. But the ridesharing company's net loss also widened, and its outlook called for sharply slowing growth. 

In its hotly anticipated initial earnings report out Tuesday afternoon, the No. 2 ridesharing service said revenue jumped 95% to $776 million, easily beating estimates of $739.5 million. Active riders jumped 46% on a year-over-year basis to 20.5 million, or 10.2% sequentially from the 18.6 million it had at the end of last year.  

A rider in the back of a Lyft car

Image source: Lyft.

On the bottom line, it reported a GAAP loss of $1.14 billion, but adjusting for $860 million in stock-based compensation and other special charges, the company finished with a loss of $211.5 million, or $9.02 a share. That's a slight improvement from the adjusted net loss of $228.4 million it had in the year-ago quarter. That result was also better than the average analyst expectation of a loss of $274 million.   

Lyft showed progress in other metrics as well. Its contribution margin, or the money it keeps from each ride before indirect expenses (operations, sales and marketing, management, and research and development) rose from 35% to 50%. Contribution profit soared 174% to $384.9 million.

CEO Logan Green called the quarter "a strong start to an important year," adding, "We are still in the very early stages of an enormous secular shift from personal car ownership to Transportation-as-a-Service."

In its second-quarter outlook, Lyft called for revenue of $800 million to $810 million, up 59% to 60% from a year ago, and an adjusted EBITDA loss of $270 million to $280 million. For the full year, it sees $3.275 billion to $3.3 billion in revenue, or an increase of 52% to 53% from last year, and an adjusted EBITDA loss of $1.15 billion to $1.175 billion, which compares to a loss of $943.5 million the year before.

The first-quarter results should please investors, as they show Lyft's momentum continuing and signal market-share gains from rival Uber (NYSE: UBER), which is scheduled to start trading later this week. However, Lyft's guidance calls for a sudden deceleration in revenue growth over the coming quarters.

Management may just be playing it safe, giving conservative guidance in its first public report so it can overdeliver later. But the weak outlook seems to be the reason the stock was trading down 2% in after-hours trading as of 5 p.m. EDT.