Ashlee Simpson's representative has failed to rule out rumours the pop star is pregnant, after the singer fuelled speculation she was expecting when she stepped out recently with noticeably larger breasts.

Rumours of a rushed wedding immediately surged speculation Simpson and rocker beau Pete Wentz were expecting their first child, following the Fall Out Boy's proposal to the 23-year-old pop star last month.

Simpson and Wentz have repeatedly dodged questions surrounding the alleged pregnancy and have so far refused to confirm or deny reports they plan to exchange nuptials next week in Santa Barbara, California.

But, while refusing to comment directly on the baby reports, Simpson's spokesperson tells the New York Daily News of her noticeably bigger assets, "It's probably just a great bra, like any girl's secret."