We're sure their daughter, two-year-old Luna, is also thrilled to meet her little brother early.
The mum took to Twitter and wrote, "Somebody's here!"
Before adding: "Wanna hold my boy let's do thisssssss'". "I mean I knew I was pregnant at 11 days in".
And Chrissy had previously admitted her second pregnancy has been a lot harder than the first time around.
Last month (Apr18), Chrissy's close friend Kim Kardashian threw her a lavish baby shower in Los Angeles, with guests treated to Shake Shack burgers and milkshakes as well as five huge cakes.
"She's used to being the centre of everything right now so we'll see how she adjusts to sharing the spotlight".
And, of course, congrats to John and Chrissy on their growing family!
Congrats, Chrissy and John!
The 32-year-old - who married the All of Me hitmaker in 2013 - previously defended the couple's decision to have a child via IVF again.