The morning-after pill works primarily by delaying or disrupting ovulation, which prevents fertilization. It does not terminate an existing pregnancy or interfere with implantation once it has occurred. The two main types of emergency contraception—levonorgestrel and ulipristal acetate—function by altering hormonal signals that trigger the release of an egg from the ovary. By postponing ovulation, they reduce the chance of sperm meeting an egg. These methods are most effective when taken as soon as possible after unprotected sex.
Despite widespread use, many people misunderstand how emergency contraceptives function. A 2021 study found that over half of participants gave incorrect explanations, highlighting a gap in public knowledge. The term “morning-after pill” is misleading, as it can be taken up to several days after intercourse and is not limited to the morning. Understanding the actual mechanism helps clarify that these pills are preventive, not abortive, and work before pregnancy begins.