Kylie Jenner shot the new Calvin Klein campaign just three weeks after she gave birth.

The Kardashians-Jenners in the new Calvin Klein campaign (c) Instagram

The Kardashians-Jenners in the new Calvin Klein campaign (c) Instagram

The 20-year-old reality TV star stripped down to her underwear - flaunting her post-baby body - in the shoot alongside her sisters Kim Kardashian West, Kourtney Kardashian, Khloe Kardashian and Kendall Jenner after she was asked to star in the campaign shortly after giving birth to her baby daughter Stormi, now six months.

Taking to her Instagram account, Kylie said: "Shot this beautiful campaign for @calvinklein by @willyvanderperre just 3 weeks after i gave birth! #ad I also love that baby true joined us for the shoot. Such special pics (sic)."

But the fivesome weren't alone in the campaign as Khloe - who has since given birth to her daughter True - was heavily pregnant when she slipped into the new CK lingerie.

Khloe, 34, posted an Instagram video showing the her rocking on a swing and rubbing her baby bump while a rendition of 'You are my sunshine' was played over the top.

She wrote: "Being in a @calvinklein campaign has always been a dream but shooting one with my sisters and being almost nine months pregnant is so special to me!

"I have this magical moment in time documented forever. Thank you Hrush for capturing these moments!!! I miss my tummy now (sic)."

Kim, 37, shared a black and white shot of all the sisters on her social networking site but opted for a different photo as she and Khloe emphasized the autumn sports bra and knickers, while Kendall, Kourtney and Kylie modelled the new jean collection.

Calvin also jumped on the social media bandwagon as he shared a vintage style video, shot in a forest, featuring both Kourtney, 39, and Khloe swinging on a wooden swing, 22-year-old Kendall laying on a tree, while Kylie and Kim sat on a picnic blanket.

He wrote: "Daughters. Sisters. Mothers. Friends. Shot in March "2018, @kimkardashian, @kendalljenner, @kourtneykardash coordinate with new "mom @kyliejenner and mother-to-"be @khloekardashian in #Fall2018#CALVINKLEINJEANS and the new Monogram essentials "from #CALVINKLEINUNDERWEAR. (sic)"