Abstinence

This is the only 100% sure way of preventing pregnancy and STIs. It is an option for couples who do not want to have sex because they don't feel ready, for religious reasons, because they do not want to use other forms of contraception, or any other personal reason.

• Chance of getting pregnant: 0.

Natural contraception

This means working out 'safer' times to have sex. If a woman has a very regular cycle, eggs will be released (ovulation) approximately 14 days before the next period and can be fertilised for up to two days afterwards. A sperm can fertilise an egg four or five days after you have sex. So if the woman has a 28-day cycle, she can get pregnant from day 10 to day 17. If her cycle is shorter or longer, count back 14 days from the period. A woman can also tell when she is ovulating by taking her temperature every day with a special ovulation thermometer that shows fractions of degrees or by looking at how much and how thick the discharge from her vagina is at different times of the month. You need detailed advice on this method: it takes commitment and great care. The Natural Family Planning Association can provide skilled help and support (see contact details below).

• Chance of getting pregnant: 2-24%.

Withdrawal

This is sometimes called coitus interruptus and means the man pulls his penis out of the vagina before he ejaculates. It takes a lot of self control and can fail if the man does not withdraw fast enough or some sperm leak out before he ejaculates.

• Chance of getting pregnant: 25%.

Barrier methods

These stop the sperm from reaching the woman's tubes. They also give some protection against STIs. However, they can interrupt sex and be fiddly to put on until you get used to them. You must remember to have them with you and to use them every time.

Spermicidals

This includes creams, foams, gels or tablets inserted in the vagina (pessaries) that kill sperm. They should be used with other barrier methods. They protect against some STIs.

• Chance of getting pregnant: 10-18%; 2% with condoms or diaphragms.

Condoms or sheaths

They are made of rubber, often with spermicide on the outside. They are put on over a man's erect penis before intercourse to stop the sperm going into the woman's vagina. They can also help prevent STIs and may be used for this reason alone, along with other methods of contraception. They should always be used with lubricants to make them less likely to break. Use only water-based lubricants - others can damage the condoms. Condoms are cheap and easy to buy, but they can burst or slip off. The man also has to withdraw soon after climaxing and hold the condom on his penis while withdrawing, to prevent any leakage of sperm.

• Chance of getting pregnant: 2-10%, depending on proper use and using spermicides.

Diaphragms or caps

Diaphragms or caps are rubber domes that a women inserts high into her vagina, covering the opening of the womb (cervix). They should be used with spermicide cream or jelly and left in the vagina for at least six hours after intercourse. They must be fitted by your doctor or family planning clinic, stored carefully and renewed every year. They give some protection against STIs. To use them, you need to feel OK about inserting your finger into your vagina and touching your genitals. Some people find them messy and fiddly. They can cause bladder infections.

• Chance of getting pregnant: 2-17%, depending on proper use and using spermicides.

Intrauterine methods

These stop the sperm from reaching the egg and make it hard for the egg to bury itself in the lining of the womb. They do not interfere with sex (although the man may be able to feel the string), are very effective and can stay in place for up to five years. They must be fitted by a doctor or at a family planning clinic. They are most suitable for women who have had a baby and who only have one sex partner. There are two main types:

Intrauterine contraceptive devices (IUDs, IUCDs, coils, loops)

Intrauterine contraceptive devices are small, plastic and copper devices put into the womb. They have a small nylon 'tail' that comes out through the opening of womb and is used to remove the device. They are usually changed every three to five years. They may make your periods longer and heavier. There is a small (1%) risk of pelvic infection when the IUD is inserted but careful insertion by a doctor can minimise this risk.There is also a greater risk of pelvic infection due to an STI if an IUD is present, so this method of contraception is better for those in staple, single-partner relationships. If you become pregnant with an IUD in, see your doctor immediately.

• Chance of getting pregnant: 1%

Intrauterine systems (IUSs)

Intrauterine systems are small plastic systems which are inserted in the uterus and release progesterone. They are suitable for women with heavy periods, because they usually make the periods lighter, or may result in you having no periods. They may cause irregular bleeding at first.

• Chance of getting pregnant:  less than 1%.

The Pill

The combined contraceptive pill contains the female hormones oestrogen and progesterone and stops the ovaries from releasing an egg each month. It is usually taken for 21 to 22 days a month (active pills). Some packets contain seven inactive pills to make up the 28-day cycle, making pill-taking easier to remember.

The Pill is simple to use, does not interfere with sex, makes periods more regular and you have less chance of getting cancer of the womb or ovaries. However, you may have very slightly more chance of getting breast cancer and the combined pill can cause blood clots in some women. Those who are over 35, have a family history of such problems, who smoke and/or are overweight are most at risk. It is really important that you know your own medical history and that of your family and that you discuss all the risks and benefits of the Pill with whoever is prescribing it to you.

Other side effects include headaches, putting on weight, sore breasts, bloating, loss of sexual interest, irregular bleeding and thrush infections.

If you are more than 12 hours late taking a pill, you will need additional contraception according to the seven-day rule which is: take additional contraception (such as using condoms, diaphragm or abstinence) for seven days WHILE CONTINUING TO TAKE THE PILL, making sure the tablets you take are active ones. If there are not seven active pills left in the packet use ones out of the next packet. This rule also applies if you have diarrhoea or vomiting.
Chance of getting pregnant: 1-5%.

The progesterone-only pill works by making the mucous in the opening of the womb thicker and changing the lining of the womb, making it less likely that a sperm fertilises an egg or that the embryo buries itself in the womb lining. It usually has fewer side effects than the combined pill and no risk of blood clots. It may cause irregular bleeding and is not quite as effective as the combined pill. It can be used while you are breast-feeding.

• Chance of getting pregnant: 2-4%.

Depo Provera

This is progesterone given as a three-monthly injection. It may be used by women who think they may forget to take pills, or prefer not to have to think about it or who can't take oestrogen. You will have no periods while using this method. You may have a slightly increased risk of getting breast cancer and osteoporosis.

• Chance of getting pregnant: less than 1%.

Emergency contraception

This either delays the release of an egg or makes it less likely that it buries itself in the lining of the womb and can be used after you have had unprotected sex or your usual type of contraception has failed (burst condom, missed pill). High doses of hormones (two doses, 12 hours apart) can be taken up to 72 hours after unprotective sex or contraceptive failure (but the sooner the better). The pills may make you feel sick or vomit.

Another method is inserting a copper IUD within five days of expected time of fertilisation. There may be a risk of infection from an IUD and the procedure may be painful. It should not be used as regular form of contraception.

• Chance of getting pregnant: pills, 1-4%; IUD, less than 1%.

Sterilisation

This is a permanent method of contraception which stops a sperm and egg from coming together. In women it is called tubal ligation or sterilisation. Clips are put on the (Fallopian) tubes to stop the egg getting to the womb. In men, it is called vasectomy. The tubes (vas deferens) which carry sperm to the penis are cut so there is no sperm in the man's ejaculatory fluid (ejaculate).

• Chance of getting pregnant: less than 1%.

See also: Contraception

Original material provided by Auckland Sexual Health Service. Edited by everybody.