VANCOUVER, Canada — Lululemon Athletica Inc. fell after it said a shortage of a women's pants line will have a "significant" effect on financial results and will mean its first-quarter revenue will be lower than forecast.

Lululemon fell as much as 12 percent to $58.03 in extended trading yesterday, after sliding 3.8 percent to $65.90 at the close in New York. The Vancouver-based company has dropped 14 percent this year, while the Standard & Poor’s 500 Index has gained 8.8 percent.

First-quarter revenue will be as much as $343 million, down from a previous estimate of as much as $355 million, Lululemon said in a statement yesterday. Comparable-store sales will increase as much as 8 percent, compared with a previous forecast of 11 percent.

“We expect this issue will have a significant impact on our financial results,” the company said in the statement. It will report fourth-quarter earnings on March 21.

The Canadian yoga-wear retailer, which has more than 200 locations, in January forecast sales for the final quarter of its year that trailed analysts’ estimates, signaling a possible slowdown. Lululemon has reported sales growth of at least 30 percent for the past 13 quarters, according to data compiled by Bloomberg.

Certain shipments of Lululemon’s black Luon pants are too sheer and don’t meet the company’s standards, it said in the statement. The affected items are about 17 percent of all women’s pants in its stores, the company said.

--By: Leslie Patton; Editors: Ben Livesey, Stephen West