Singer and fashion designer Jessica Simpson is proudly flaunting her stunning post-baby physique.

The star, 39, took to instagram to share a gorgeous photo of herself to celebrate dropping 100 pounds since welcoming third child Birdie Mae in March. Simpson can be seen in a black dress with a cinched waist and she captioned the post: "6 months. 100 pounds down. (Yes, I tipped the scales at 240)."

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Simpson also added that the first trip away from her baby daughter was very emotional for many reasons, but she was so proud to feel like herself again. She also included an adorable picture of her holding little Birdie.

Simpson's trainer, Harley Pasternak, shared Simpson's photo to congratulate her and say how proud he was of her.

"Beyond proud of this incredible woman. Been working together for over 12 years and she’s always the most warm, sweet, polite, and respectful person in the world. And on top of it all, after being nonstop pregnant for as long as I can remember, she’s down 100 pounds and looks younger today than she was when we met," Pasternak wrote.

Simpson has not revealed exactly how much she gained during her third pregnancy. The American Pregnancy Association says that weight gain during pregnancy varies based on pre-pregnancy weight. For women with a BMI of 18.5 to 24.9 (“average weight”), their guideline is 25 to 35 lbs, PEOPLE reports.

"It's not easy at all, but I am determined to feel good," she told People. The star, who's also mom to daughter Maxwell, 7, and son Ace, 6, (with hubby Eric Johnson), said she was shedding pounds thanks to exercise and healthy eating.

"I have been doing a lot of walking — getting my steps in not only burns calories but it also helps me clear my head and get focused," she said.

Along with her daily steps (Simpson previously told PEOPLE that she tries to walk three miles a day with her husband and their kids), she was also making improvements to her diet. The Texas-born singer was surprised to discover at least one healthy new favourite. She found that she absolutely loves cauliflower and it sure helps that it can be used as a substitute for almost anything.

Simpson has often struggled with her weight in the past and even once had a deal as a celebrity spokeswoman for Weight Watchers, now known as WW, or Weight Watchers Reimagined.

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Tags: Weight, Instagram