I'm an uncle!

I got the news last night that my sister in law gave birth to a baby boy. I wonder why people always specify that it was a "baby" boy. Is that really a necessary adjective? Are there a lot of people who give birth to full grown boys, such that you'd have to specify to avoid confusion?

"Really? you had a boy? a baby one or full grown? a
teenager? that must've been painful!"

I don't know if it was a "bouncing" baby boy because no one dropped him, but he appears to normal in all other aspects. In fact, better than normal...exceptional! Very handsome. He looks strong too (a future jiu jitsu fighter? one can only hope).