Celebrity parents-to-be Ashlee Simpson and Pete Wentz have prompted speculation they are expecting a son, after embarking on a shopping spree for baby clothes.

The couple announced Simpson's pregnancy last month, just weeks after their wedding ceremony in California.

They have refused to reveal the unborn baby's gender - but staff at Los Angeles boutique Petit Tresor claim they dropped big hints it will be a boy.

A source tells Ok! magazine, "Almost everything (they picked out) is blue."

The couple's shopping list reportedly included a bib with "hunk" written on it, and a number of other clothes.

The source adds, "They made it very clear that it was a boy."