The couple already have a baby daughter, Luna Simone who was born in 2016, and Chrissy has shared her second pregnancy with her followers on social media.
Teigen tweeted the news late Wednesday night, writing, "Somebody's herrrrrrre!" followed by a series of baby bottle emojis.
The "Sports Illustrated" model took to Twitter to announce her and husband John Legend's second child had arrived in the world.
Before adding: "Wanna hold my boy let's do thisssssss'".
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Their newborn son joins the couple's 2-year-old daughter, Luna. "I mean I knew I was pregnant at 11 days in".
Venting her frustration on Twitter, she wrote: 'Happy pregnant Chrissy is gone. meet OVER IT Chrissy. She previously posted on Instagram that they were expecting a boy.
Explaining why she had reached her final tether, Chrissy said that things were more frustrating because she had known about her pregnancy for so long. She captioned the announcement video: 'It's John's!' I think she'll probably have some growing pains because she's currently running the house right now.
The couple married in 2013.