"It’s a boy," the reality star and businesswoman added.
"What!" her sister, Kourtney Kardashian, shouted in response to Kim telling the world.
"Well, it's out there," she added about the gender reveal.
"I got drunk at our Christmas Eve party and I told some people. And I can’t remember who I told because I never get drunk," Kardashian West said.
The couple is already parents to daughter North, 5, son Saint, 3, and daughter Chicago, 11 months. A surrogate carried and gave birth to Chicago, as well.
It's been a big year for Kardashian West. In addition to her new baby, she was instrumental in the release of Alice Johnson, a 63-year-old grandmother serving a life sentence on drug charges.
She met with President Donald Trump last year to talk about getting Johnson released and was actually the one who got to tell her that this dream of freedom was a reality.
"I was free," Johnson said Kardashian West told her this past summer. "I was going to rejoin my family."