Twitter has reported lower than expected revenue for the first three months of the year, saying that new products sold less well than forecast.
The micro blogging firm warned that it expected the negative impact on its revenue to continue for the rest of the financial year.
"It is still early days for these products," said Twitter chief executive Dick Costolo.
The firm reported revenues of $436m, up 74% year-on-year, but below forecasts.
It also reported a net loss of $162m, an increase from the same period a year ago when it lost $132.4m.
However, monthly users of the service increased 18% year-on-year, totalling 302 million for the first quarter.
Mr Costolo said the firm remained confident in the firm's "long-term opportunity".
"We have a strong pipeline that we believe will drive increased value for direct response advertisers in the future," he added.
Twitter also said it was buying marketing technology firm TellApart, and announced a deal with Google to improve its advertising performance measurement.
The firm said it expected revenue for the full year to be between $2.17bn to $2.27bn, lower than the $2.3bn to 2.35bn range it forecast in December.
Shares fell 18% after the results were released earlier than expected and before US markets closed.