Emergency contraception pills work by preventing ovulation, fertilization, or implantation.

It is classified as a contraceptive and acts in most cases by preventing ovulation or fertilization.

But contraception, by definition, is the use of any method to prevent fertilization and pregnancy.

An example of this conflict might be a person using birth control to prevent fertilization and thereby inhibit the replication of his or her genes.

This prevents accidental fertilization of the female plants, either to facilitate sinsemilla flowering or to provide more control over which male is chosen.

They work primarily by preventing ovulation or fertilization.

While they are believed to prevent implantation rather than fertilization, exactly how these effects operate to prevent pregnancy is not understood.