Jessica Simpson is proud of her postpartum body.

In an Instagram post Tuesday, the clothing designer announced that she'd lost 100 pounds since giving birth to her daughter, Birdie Mae, this past March.

During her pregnancy, she "tipped the scales at 240," she wrote in the post.

PHOTO: Jessica Simpson is seen in this undated photo she posted to her Instagram account.
Jessica Simpson via Instagram
Jessica Simpson is seen in this undated photo she posted to her Instagram account.

"My first trip away from #BIRDIEMAE and emotional for many reasons, but so proud to feel like myself again," she wrote. "Even when it felt impossible, I chose to work harder."

(MORE: Jessica Simpson shares adorable photo of lookalike daughters)

In addition to baby Birdie, Simpson, 39, and her husband, former NFL player Eric Johnson, 40, are parents to daughter Maxwell Drew, 7, and son Ace Knute, 6. To get back in shape after each pregnancy, Simpson, a former spokeswoman for Weight Watchers, now known as WW, has worked out with celebrity trainer Harley Pasternak, who reposted her photo from Tuesday.

"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," he captioned the post. "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."