The morning after pill is definitely not 100% effective but works in about 90% 
of the cases. The morning after pill can be taken within 72 hours of sex. The earlier you take the better it is, because it works best within 12 hours of unprotected sex.
All emergency contraceptive pills prevent the attachment of a fertilized egg to a woman’s uterine wall. Four different types of morning after or emergency contraceptive pills are available:
- The first type of morning after pill contains a female hormone known as progestin. These pills can reduce your pregnancy risk by 87%. These progestin only pills have significantly lesser side effects than ‘combination pills’. However, they can cause some irregular bleeding and mood swings.
In the event that the eggs become fertilized within 72 hours of unprotected sex, these pills can still halt the fertilized egg from attaching to the walls of the uterus.
These types of morning after pills interfere in your menstrual cycle by affecting the hormone level. These pills can be taken as late as 5 days after unprotected sex. However, they are most effective when taken within the first 24 hours. These pills contain 0.75 mg of levonorgestrel.
- The second type is a combination emergency contraceptive pill that contains both the hormones: progestin and estrogen. These pills reduce the risk of your pregnancy by 75%. They can cause side effects such as nausea, vomiting. If you vomit within an hour of taking the medicine, you will have to take the pill again. You can take an anti- nausea drug one hour before taking the morning after pill to counter the feeling of nausea.
- These pills usually contain 0.25 mg of levonorgestrel and 0.05 mg of estrogen and they are taken in two doses. Estrogen works by trying to prevent ovulation.
The third type of morning after pill contains ulipristal acetate. It is found to be highly effective and is tolerated well by the body. These pills are available only in Europe.
The fourth type of morning after pill has low amounts of mifepristone. These pills are very effective contraceptives and are found to have fewer side effects. Mifepristone is a steroid. The pill can be taken during the first 2 months of pregnancy for the purpose of abortion. This form of pregnancy prevention should be taken as a last resort when it is too late to have morning after pill.
You should remember that morning after pills are to be used for contraception in emergencies only and not regularly.
