The Lottery is a lottery system within the Silo which is used to decide who was eligible to get pregnant—it was implemented and controlled by Judicial as a form of population control. Those who 'win the lottery' are given a full calendar year to fall pregnant, before having their implant re-instated.
Allison and Holston Becker were known throughout the Silo as being lucky enough to win the lottery twice. Both times, however, Allison failed to fall pregnant—it was later revealed that this was deliberate and that her implant had not been removed.