Critics of the Bible often point out that Jesus's trip to Egypt, along with the wise men's visit, are not mentioned in Luke's account of Christ's birth.
This is a general rule for almost every single "contradiction" raised in the Gospels - one will often give details that the other doesn't.
For some reason, critics of the Bible cannot understand that omitting something from an account is not the same thing as stating it didn't happen. This should be common sense, but then again, we are dealing with people who believe that the human body could arise via natural processes, so we can't assume common sense.
I've arranged the events in the order that they happened chronologically taken from the accounts in Matthew and Luke chapter 2:
We use the common event of the family's return to Nazareth to sync the two accounts. Nothing contradicts, they simply both give details that the other doesn't. That's why we have 4 Gospels.