Emergency contraception is a method used to prevent a pregnancy that may have resulted from an act of unprotected intercourse. This can occur through a burst condom or a dislodged diaphragm, or having missed taking the pill or having had sex using no contraception at all. Emergency contraception can also be used to prevent pregnancy after a woman has been forced to have sex against her will.
Emergency contraception can involve either having an intra-uterine device (IUD) inserted or taking emergency hormonal contraception as soon as possible after the event. Emergency hormonal contraception is sometimes referred to as ‘the morning after pill’, although this can cause confusion since it should be taken as soon as possible after unprotected sex, not necessarily in the morning. Most doctors and pharmacists are familiar with prescribing emergency contraception, but if not, your family planning clinic or women’s health centre should be able to help you.
In the normal course of events when a woman becomes pregnant, one of her ovaries releases an egg (ovulation) which is fertilised by sperm swimming up the fallopian tubes. The fertilised egg then passes down the fallopian tube into the uterus, where it embeds itself into the lining of the uterus.
Emergency contraception stops the fertilised egg from implanting in the lining of the uterus (womb). This is true of intrauterine devices and also hormone pills. In addition, when hormone pills are used and they are given in the part of the menstrual cycle before ovulation they may also delay the release of the egg, which will prevent fertilisation of the egg happening in the first place.
Delaying the release of the egg can be crucial if there are sperm present because sperm can still fertilise an egg for many hours and even days after ejaculation. The average survival is 2 to 3 days although some sperm can survive for 5 to 7 days.
Theoretically, it is possible for sex taking place 5 to 7 days before ovulation to result in pregnancy and also sex taking place a day or so after ovulation to result in pregnancy (the egg is only viable for up to 24 hours after its release from the ovary).
Emergency contraception should only be used if a single act of unprotected sex has occurred since your last period. If there has been more than one act the doctor has to rule out the possibility of a pre-existing pregnancy. The use of emergency contraception is ineffective if implantation has already occurred. Also, emergency contraception might do some harm if you are already pregnant.
Some of the advantages of emergency contraception are that:
The main advantage of using hormonal emergency contraception is that it is easy to use. The main advantage of using an IUD is that it offers ongoing contraception.
Some of the disadvantages of emergency contraception are that:
The main disadvantage of using an IUD is that it is not particularly suitable for young women who have not had children.
The way that you use emergency contraception depends upon the method selected.
The hormonal contraceptive pills approved in Australia for emergency contraception contain a progestogen called levonorgestrel. Their brand names are Postinor-1, Postinor-2, NorLevo, NorLevo-1, Levonelle-1 and Levonelle-2. They are available from pharmacists without a prescription. Depending on the particular brand used, you will need to take either one or two tablets as soon as possible after unprotected sex, or one tablet as soon as possible and a second one exactly 12 hours later. Your doctor or pharmacist will explain how you should take the emergency contraceptive pill.
These newer progestogen-only pills are more effective than the older methods of having to take multiple tablets of the progestogen pill or taking combined hormonal emergency contraception. They also cause fewer side effects such as vomiting.
Alternatively, a copper IUD (such as Multiload-cu 375 or TT380) may be inserted by your doctor or at the family planning clinic within 5 days of unprotected intercourse, or in some cases up to 5 days after the earliest estimated day of ovulation if intercourse took place more than 5 days beforehand.
The effeciveness of emergency contraception depends on the method used. It has been estimated that the progestogen-only contraceptive pill will prevent 85% of pregnancies if taken within 72 hours of unprotected sex. The sooner you take the pill, the more likely it is to be effective.
The copper IUD method of emergency contraception is more than 99% effective in preventing pregnancy.
Last Reviewed: 06 January 2010