Oh, baby!

Kim Kardashian West and her rapper husband, Kanye West, have welcomed baby number four, born Thursday via a surrogate.

The beauty guru and "Keeping Up With the Kardashians" star announced the news Friday afternoon, tweeting to her more than 60 million followers: "He's here and he's perfect!"

A rep for the reality star said he weighed 6 pounds, 9 ounces.

Kardashian, 38, did not offer any additional details on the birth but said he's "Chicago's twin," referring to her youngest child who was born last year, also via a surrogate.

Kardashian has not yet shared a picture of her baby boy and did not say what they will name him. West has not publicly commented on the birth.

According to TMZ, the couple's surrogate went into labor on Thursday. Kardashian was supposed to be at a taping of "The Ellen DeGeneres Show" that day but could not make it because she was at the hospital, sister Kourtney Kardashian revealed in a video clip DeGeneres shared on her Twitter account.

Kardashian and West, who married in May 2014, are already parents to North, 5; Saint, 3; and Chicago, 1. The couple chose to use surrogates for the births of their last two children after Kardashian experienced complications during her pregnancies with North and Saint.