Katherine Heigl has shared a series of images showing her transformation as she shed her baby weight.

The former Grey’s Anatomy actress, 39, welcomed son Joshua Jr in December 2016.

She posted three images of herself in underwear and swimsuits on Instagram, telling her followers it took her 14 months to “find those ab muscles and get my butt back up where it belongs”.

It’s been almost 14 months since Joshua Jr was born and it has taken me about that long to really get back in shape. The first pic was taken one month after he was born. The second pic was taken almost a full year later and the last pic was taken this weekend. I wish I had a few from in between the first and second so you could really see how slow my progress was but alas…I was busy covering it all up those months, not posing in my unders! Anyway, I have a beach vacation coming up, a new job I start filming in April and my deep desire to feel fit, strong and sexy propelling me forward the last two months to finally loose the last of my baby weight and do a deep dive search for the ab muscles I knew were buried under that belly somewhere! I was wholly and totally inspired by Miss @rachparcell and the before and after pics she shared after taking the #bbg challenge. I had never heard of it but she looked so damn great (she had her baby just a few months before me) that I had to check it out. I found a fantastic app called #sweat that features several different #bbg programs you can choose from and makes it incredibly easy to do anywhere, which for me means in my bedroom at home! I won’t lie, the workouts are real ass kickers but the progress I’ve made in only 5 short weeks has kept me motivated and inspired to keep going! I am so grateful I’ve had a full year to find those ab muscles and get my butt back up where it belongs and wasn’t forced by work to snap back into shape but it is time to make the strength, fitness and overall health of my body a priority and I am so grateful that @rachparcell shared her story and got this mama motivated!

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Heigl, who has been cast in Meghan Markle’s old show Suits, said: “It’s been almost 14 months since Joshua Jr was born and it has taken me about that long to really get back in shape.

“The first pic was taken one month after he was born.

“The second pic was taken almost a full year later and the last pic was taken this weekend.

“I wish I had a few from in between the first and second so you could really see how slow my progress was but alas…I was busy covering it all up those months, not posing in my unders!

“Anyway, I have a beach vacation coming up, a new job I start filming in April and my deep desire to feel fit, strong and sexy propelling me forward the last two months to finally loose the last of my baby weight and do a deep dive search for the ab muscles I knew were buried under that belly somewhere!”

The actress said she had been “wholly and totally inspired” by blogger Rachel Parcell’s before and after images and used an app featuring workouts to help her get in shape.

“I won’t lie, the workouts are real ass kickers but the progress I’ve made in only 5 short weeks has kept me motivated and inspired to keep going!” she said.

“I am so grateful I’ve had a full year to find those ab muscles and get my butt back up where it belongs and wasn’t forced by work to snap back into shape but it is time to make the strength, fitness and overall health of my body a priority and I am so grateful that @rachparcell shared her story and got this mama motivated!”

Heigl and her husband Josh Kelley also have two adopted daughters, Naleigh and Adalaide.