That explains it. Actually, of course, it didn't explain anything, but whenever doctors are confused about something, which is really more frequently than any of us would do well to think about, they always snatch at something in the vicinity of the case and add, That explains it. If Fezzik's mother had come late, they would have said, Well, you came late, that explains it. Or Well, it was raining during delivery, this added weight is simply moisture, that explains it.)
A healthy baby doubles his birth weight in about six months and triples it in a year! He leafed through them, found the one he wanted and replaced the others!