The morning-after pill, a type of emergency contraception, is commonly used to prevent pregnancy after unprotected sex. It is generally effective and safe. Possible side effects may include nausea, vomiting, abdominal pain, fatigue, dizziness, changes in menstrual cycle, and headaches.
Conception usually does not occur immediately after intercourse but rather one to several days later. During this time, sperm travel through the fallopian tubes to meet an egg. Therefore, taking the morning-after pill is often not too late.
The active ingredients in the morning-after pill are similar to those in regular contraceptive pills but in higher doses. Some morning-after pills contain only one hormone (levonorgestrel), while others contain two hormones (estrogen and progestin). Estrogen can inhibit ovulation, while progestin works to prevent sperm from meeting the egg or to stop a fertilized egg from implanting in the uterine lining (embryo implantation).
Statistics show that taking the morning-after pill after unprotected sex has an efficacy rate of over 80%.
The morning-after pill is different from what is commonly referred to as the abortion pill (mifepristone). Emergency contraception is intended to prevent pregnancy, whereas abortion pills terminate an established pregnancy by stopping the development of a fertilized egg that has already implanted in the uterine wall.