A player can be placed on the Paternity List when he leaves his club to attend the birth of his child.
A player must remain on the Paternity List for at least 24 hours, but no more than 72 hours.
The Paternity List functions like a Disabled List or Bereavement List, in that a player on Paternity Leave does not count against his club's Active List, so he can be replaced by another player while on the Paternity List. He does count against his club's Reserve List (40-man roster), however.
An MLB player continues to accrue MLB service time while on the list.