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Jessica Simpson shows off her post-baby body (and a big smile) in a new picture she shared while working on her latest Weight Watchers ad.

Couldn’t stop smiling on set for my new @weightwatchers campaign today! #happy,” wrote the fashion entrepreneur.

Simpson gave birth to son Ace four months ago, and has an 18-month-old daughter named Maxwell.

Last week, she shared some life lessons she hoped to impart to her children.

Simpson wore a head-turning black dress on a triple date with sister Ashlee and friend CaCee Cobb earlier this week.