Teen apparel retailer Aeropostale forecast a bigger-than-expected loss for this quarter as it struggles to keep pace with changing fashion trends.

Aeropostale shares fell 18 percent in extended trading at $3.70. They traded at above $15 a year earlier.

Teen apparel retailers have been losing out to fast-fashion brands such as H&M, Forever 21 and Zara, which bring in latest styles from the runway to its stores within weeks.

Aeropostale, whose stores are located mostly in shopping malls and have been struggling to attract shoppers in recent quarters, said it expects current-quarter loss of 55-61 cents per share.

Analysts on average were expecting a loss of 50 cents per share, according to Thomson Reuters I/B/E/S.

The company's comparable sales, including online sales, decreased 13 percent in the first quarter ended May 3, compared with a 9.7 percent decline expected by analysts polled by Consensus Metrix.

Aeropostale has reported declining comparable sales for seven straight quarters.

Gap Inc said its comparable-store sales fell 1 percent and profit plunged 22 percent in the first quarter, while Urban Outfitters Inc reported a lower-than-expected quarterly profit.

TJX Cos Inc, the owner of off-price chains TJ Maxx and Marshalls, and American Eagle Outfitters Inc gave disappointing outlooks.

Aeropostale's first-quarter Net loss widened to $76.8 million, or 98 cents per share, from $12.2 million, or 16 cents per share, a year earlier.

Excluding items, the retailer posted a loss of 52 cents per share. Analysts expected a loss of 72 cents per share.

Net sales declined about 12 percent to $395.9 million, below the $410 million that analysts estimated.

The company said it shut down 18 Aeropostale stores during the quarter.