With the simple caption "Psalm Ye" - father Kanye West is often referred to as "Ye", an abbreviation of his first name - the photo shows the one-month-old baby sleeping.
After the child's birth was announced in May, Kardashian West shared a screenshot of a text message conversation with her husband which included a picture of their baby in a crib and the words: "Beautiful Mother's Day with the arrival of our fourth child".
In May, the Keeping Up With The Kardashians star tweeted the new baby looked just like her daughter, Chicago. "We have everything we need", Kardashian tweeted, along with the snap.
Kim, 38, suffered through hard pregnancies with North and Saint, so turned to surrogacy for her third and fourth children.More news: Kevin Durant Planning to Play in Game 5 of NBA Finals
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Daughters Chicago, 16 months, and North, 6, and son Saint, 3, all do not have middle names.
It seems that the two of them turned up at the Bootsy Bellows club in West Hollywood in order to celebrate their mutual friend Stassie Karanikolaou's birthday.
Although one-year-old Chicago was too young to understand that a new baby was coming, the E! reality star said in January that North and Saint were looking forward to the addition. Kardashian wrote on Twitter at the time.