'What's up with Kim's face?' Kourtney Kardashian shares first snap of sister since Saint's birth... but fans hardly recognise her

She's stayed out of view for weeks since giving birth to son Saint early last month.

But Kim Kardashian made a return to the spotlight in an unexpectedly low key fashion with an appearance on sister Kourtney's Instagram feed on Sunday.

The image sparked a huge response from fans - but it wasn't her svelte post-baby body that they were surprised by.

'Studio hoes. #SWISH!' Kourtney Kardashian shared a picture of herself and sister Kim on Sunday morning; it was the first image of the new mother since she welcomed son Saint in early December

'What's up with Kim's face?' Many fans speculated Kim had used her time out of the spotlight to have some work done on her appearance

Instead fans speculated about the reality star's face, with many suggesting that she had used her time out of the spotlight to have some work done.

'What's up with Kim's face?' wrote one commentator, while others remarked that she looked almost unrecognisable.

'Post Botox Kimmyyyy?????' added another, while many speculated that fillers or Botox had changed the mother-of-two's appearance. 

See more of the latest on Kim Kardashian as she resurfaces looking unrecognisable 

And another one: Later on Sunday Kourtney posted a picture of all three sisters, taken by Kim

Snap happy:  A second image showed Kourtney with Kylie, and was captioned simply 'SWISH'

And while Kourtney had tagged the post with her sister's name, some fans even argued that it wasn't the 35-year-old in the picture, so different did she look.

The image, which Kourtney posted with the caption 'Studio hoes. #SWISH', showed the sisters dressed head to toe in black.

Kourtney stood at the front of the image, phone in hand, hair down over her shoulders.

Changing faces? Kim is pictured while pregnant with Saint, left, then back in 2007

'What's up with Kim's face?' One commentator wrote on Instagram, while others remarked that she looked almost unrecognisable

'Post Botox Kimmyyyy?????' Another Instagram follower wrote, while many speculated that fillers or Botox had changed the mother-of-two's appearance

Kim, hair in a messy chignon, stood partially obscured by her 36-year-old sister, snapping a photo on her own phone.

A second image showed Kylie Jenner and Kourtney in a similar pose. 

While Kim has not posted any new snaps of  herself since welcoming Saint on December 5, she has been busy updating her paid for website, using plenty of flashback snaps.

And it seems her fans may have a point, with old snaps of the star showing her face looking remarkably different to Kourtney's Instagram.

Who nose what's changed? There is no denying that her looks have evolved, as she is pictured here with Paris Hilton in Los Angeles back in 2006

Previously, Kim was angered by speculation she used fillers while pregnant.

Last summer she wrote on Instagram: 'No I don't do fillers or Botox when pregnant like some tabloids are reporting, you would have to be really sick to endanger your child like that!

'Anyone who has been pregnant or gained weight knows your face totally changes! My nose gets bigger, cheeks fuller & my lips swell up.'

She was responding to InTouch magazine's claims she had Botox fillers 'every three months' to maintain her 'signature look'.

KimYe! The pair are seen last October; Kim denied she had any fillers done while pregnant

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However Kim has copped to using Botox before and has even had a bad reaction from it as seen on season five of her hit reality show.

In the episode aired in September 2010, the stunner felt uncomfortable after visiting a Beverly Hills clinic for the procedure as she was accompanied by younger sister Khloe.

After the injections, Kim began complaining about irritation on her face including itching and her eyes constantly watering.

Kim then said during a confessional session: 'The doctor did warn me about side effects from the botox, but I am feeling like my eyes are on fire.'

Unrecognisable: While Kourtney had tagged the post with her sister's name, some fans even argued that it wasn't the 35-year-old in the picture, so different did she look