And two days after sharing the news the pregnant singer and her actor-musician spouse were spotted looking blissfully happy while out to breakfast in Beverly Hills, California.
After their meal, the couple left to do some last-minute Christmas shopping with Ashlee, 30, dressing her pregnant figure in an all-black chic ensemble.
The Pieces Of Me singer wore black skinny jeans with a long striped top and a black fur coat over top.
She accessorised with black buckled ankle booties, a large leather handbag with Mickey Mouse-like white shapes on the front, and dark exaggerated sunglasses.
Evan, 26, opted for a more casual style in baggy distressed jeans and an oversized gray jumper, which included embroidered wolf-theme designs.
He wore his recently bleached hair shaved close to his head, matching his wife's new shorter blonder 'do.
Last month Evan revealed to UsWeekly that he was hoping to have children with Ashlee, who has a six-year-old son, Bronx Mowgli, with her ex Fall Out Boy vocalist Pete Wentz.
'I would love to,' the actor revealed when asked if he plans on starting a family, adding that he wants 'as many as possible.'
Ross - born Næss - can currently be seen alongside Jennifer Lawrence and Liam Hemsworth in The Hunger Games: Mockingjay – Part 1.
The CrazySexyCool actor will reprise his character Messalla in Part 2, the thrilling conclusion to the franchise next November 2015.
Last week, Evan released his other baby - his new single How to Live Alone.
Meanwhile, sometime-singer Simpson - who infamously lip-synced on SNL in 2004 - hasn't released a record since her third studio album Bittersweet World back in 2008.
