Joining Andy Cohen on Watch What Happens Live, Kim confirmed the news.
"Are you working on another child?" Cohen asked.
"We are," she said.
“It’s a boy, I think it’s been out there,” the mother of three 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.”
Kourtney squealed, "Obviously I knew that, I didn't think you were telling everyone."
The baby will join big siblings Chicago, 1 this month, Saint, 3, and North, 5½.
"They love having their kids run around and be able to grow up and enjoy each other as siblings," a source told E! News, saying Kim and Kanye are "over the moon excited to have another child."
Kim, who was advised it was too dangerous for her to carry another child, turned to surrogacy to have her second daughter, Chicago. Though the Keeping up with the Kardashians star admitted she found it hard not being in control.
"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 ever 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."
Though it hasn't been confirmed whether Kim and Kanye are using the same surrogate they used for Chicago, sources say the pair would definitely have been comfortable doing that. “Kim and Kanye were already talking about baby No. 4 when Chicago was just a couple of days old. And they absolutely would use the surrogate again. They love her,” an insider told PEOPLE.
Congrats to the happy family!