Here's a video that pretty much sums up the difference between being a new MOM and a new DAD.
Tom Fletcher is a singer and guitarist in the British band McFly, and his wife just had a baby. And while she was pregnant, they made a time-lapse video to show her getting bigger and bigger.
She's on the left getting more and more pregnant as the video goes on. Meanwhile, he's on the right side of the frame singing and playing guitar. And obviously he doesn't gain a POUND.
(Search for "From Bump to Buzz." The baby shows up at 2:48.)