It all began when a fan tweeted at her about how excited they were to learn the name of Khloe's baby.
Kim and Kanye West welcomed their third child via a surrogate last Monday. But she was not able to do so this time around due to preeclampsia and placenta accreta, serious pregnancy complications she suffered from in the past.
She wrote: "Having a gestational carrier is definitely different, but anyone who says or thinks it's the easy way out is completely wrong".
She continued of their surrogate, whose identity has not been revealed: "We have a great relationship with her and trusted her completely throughout the entire process". It's not for everyone, but I absolutely love my gestational carrier and this was the best experience I've ever had. "Since we implanted my fertilized egg in our gestational carrier, our baby is biologically mine and Kanye's".
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It features the girls gleefully snuggling up on a blanket and playing games like "Never Have I Ever". Watch a video promo for the Calvin Klein campaign below.
She continued, "Kanye and I are happy to announce the arrival of our healthy, lovely baby girl".
The couple have not yet revealed their daughter's name.
Kim announced the choice of name on her blog on Friday morning, in the form of a birth announcement.
'Kim does not have any connection to the city of Chicago, but Kanye grew up there. The source went on saying, "Kim wanted to recognize Kanye's roots and do something cute, fun and unique".
Kardashian took to Instagram on Sunday to show off some of her daughter's personalized clothing, sharing a photo of a purple clothing item with "Chicago" printed on it in purple script.