Chicago recalled right-hander James Norwood from Triple-A Iowa in a corresponding move.
Players can remain on the paternity list for as little as one day and as many as three. Because Hamels' next scheduled start doesn't come until Saturday, he isn't expected to miss any action.
Hamels is 7-4 with a 3.73 ERA and 1.33 WHIP in 22 starts.
Norwood joins the Cubs for his third stint with them this season. He threw one scoreless inning for the Cubs on May 24. Norwood has a 4.28 ERA in 43 appearances at Triple-A this season.