Last night I put Luke in his little froggy sleeper and then was looking through pictures and saw one of him wearing it on his belly on Tommy's arm. So, I made them recreate the picture for a comparison.
Here he is at one week old. His feet are nowhere near the bottom and his hands are about halfway up the sleeves! It's baggy on him all over.
Now, at 5 1/2 weeks his feet are all the way at the bottom, hands are out of the sleeves, and he fills it out everywhere :)