“He’s here and he’s perfect!”, she wrote to Twitter.
Kim first announced the news on January 15, while making an appearance on Watch What Happens Live with Andy Cohen.
"Are you working on another child?" Cohen asked, to which Kim replied, "We are".
“It’s a boy, I think it’s been out there,” she added. “I got drunk at our Christmas Eve party and told some people. I can’t remember who I told because I never get drunk.”
Kim and Kanye's new baby will join siblings North, 5½, Saint, 3, and Chicago, 1.
Following the announcement, a source told E! News, "They love having their kids run around and be able to grow up and enjoy each other as siblings."
The couple once again turned to surrogacy, having welcomed Chicago via surrogate in January 2017.
Kim was advised it was too dangerous for her to carry another child, something she found "difficult" to come to terms with.
"It is frustrating, like, to not be able to do it on your own," Kim revealed on KUWTK in 2017. "It is a weird dynamic. Like I go to all the doctor's appointments and I try to be really present, but when you're not carrying it yourself it is such a fine balance of how much you're going to be in their lives. Of course, I want to know every last detail that's going on with my baby and that's super frustrating, but I really trust my surrogate and I don't want to be that person that's trying to control her every move."
Kim and Kanye's new bub joins a long list of Kar-Jenner cousins, including Kourtney Kardashian and Scott Disick's three children, Mason, 9, Penelope, 6, and Reign, 3, Rob Kardashian and Blac Chyna's daughter Dream, 2, Kylie Jenner and Travis Scott's daughter Stormi, 1, and Khloe Kardashian and Tristan Thompson's daughter, True, 9-months.
Congrats to Kimye!