The baby girl was born January 15th at 12:47 a.m. PT and weighed 3.3kg, Kim added.
The couple, who are known affectionately to fans as Kimye, already share four-year-old daughter North and two-year-old son Saint.
The couple was forced to resort to surrogacy after doctors told Kardashian-West that "it wouldn't be safe" to risk natural conception again. During her first pregnancy, she discovered that she suffers from placenta accreta, a health condition that makes labor and delivery hard.
KUWTK viewers have seen Kim's struggle to get pregnant over the years, and doctors had advised against her carrying a third baby.
"Taking to the photo-sharing platform, The Keeping up with the Kardashians star teased her followers with a topless photo while wishing 'good night".
As you may remember, the first two pregnancies were especially hard on Kim and the doctors advised her against carrying another baby. "I think it is so much harder to go through it this way, because you are not really in control". The KKW Beauty owner shared on social media in late September 2016 a pic of her wearing the piece of jewelry, which looked very similar to the one she rocked this weekend. "[North] said, 'Mom, since baby sister's not here, I think I need all of the toys in my room and I'll play with them and just make sure they're all okay for baby sister'".
And Kim Kardashian has certainly not held back on decorating the nursery for her new addition - having reportedly splurged a whopping $550,000 on baby goodies.
INSIDER has contacted representatives for Kim Kardashian West and Kanye West for comment.