January produced mixed results for retailers based in the Philadelphia area, with two apparel specialty chains reporting lower sales and the Bon-Ton department stores reporting an increase at locations open at least a year.

Sales at stores open at least a year, or same-store sales, are the main industry yardstick because they exclude the effect of store openings and closings.

Mothers Work Inc., the Philadelphia designer and retailer of maternity wear, said today that its same-store sales were down 6 percent for the month, in line with an earlier company forecast.

President Rebecca Matthias blamed the decline on colder weather last month than in January 2006, which increased sales of spring clothing, and one less Saturday, the biggest shopping day of the week, this January.

Deb Shops Inc., the Philadelphia specialist in junior apparel, said January same-store sales were $21.4 million, 0.2 percent less than a year earlier. Comparable-store sales for the fiscal fourth quarter ended Jan. 31 were down 3.7 percent, the company said.

But The Bon-Ton Stores Inc., based in York, said its sales increased 6.4 percent in the four weeks ended Jan. 27. For the 13 weeks ended Jan. 27, same-store sales were down 5.6 percent, the company said.

Across the country, retailers reported better results for the month than in January 2006, with same-store sales increasing 3.9 percent, according to the Retail Metrics data-collection service. The firm said it was the best month in sales gains since September, with drugstores and department stores leading the way.

Contact staff writer Tom Belden at 215-854-2454 or tbelden@phillynews.com.