Lululemon Athletica's shares fell about 18% in early trading on Friday, as the maker of high-end leggings warned that tariff-related costs and uneven demand in key markets of North America and China will dent its profits this year.

A “pivotal question” is whether the slowdown in the athleisure company’s U.S. business is temporary “or a sign of something more fundamental,” UBS says.

Apparel maker’s stock falls 20% after company lowers its earnings forecast, citing trade war and a pullback in consumer spending.