A situation where the size of the population does not change (remains unchanged) is called Population Stabilization. It may also be known as Zero Population Growth. The population stabilization arises when number of births plus in- migration is equal to number of deaths plus out-migration.

Birth control/ contraception/ fertility control is a method to prevent unwanted pregnancies and in turn control the population. The world's population is rapidly increasing, so it becomes necessary to control the population. There are many methods of birth control that may or may not have any effect on human body.