Contraception, or birth control, helps you prevent pregnancy and plan if and when to have children. There are many options in Australia, and they work in different ways and suit different people. No method is 100% effective, so there is always a small chance of pregnancy even when you use birth control carefully. Some methods also lower the chance of catching a sexually transmitted infection (STI), and some are used for other reasons too, such as heavy or painful periods, acne, endometriosis or PMOS. Dr Mahadik can talk through the options and help you choose what suits you.

You will often see two figures for how well a method works:

• Perfect use — how well it works when used correctly every single time.
• Typical use — how well it works in everyday life, allowing for missed pills, a condom slipping, or an injection running late.

The difference between the two figures matters. Methods you have to remember (like the pill) show a bigger difference, because it is easy to miss a dose. "Set-and-forget" methods (implants and IUDs) work out almost the same either way, because there is little you can get wrong once they are in place. Both figures are given for each method below.

Contraception is often grouped into four kinds:

• Barrier methods — condoms and the diaphragm, used each time you have sex.
• Short-acting hormonal methods — the pill and the vaginal ring, used daily or monthly.
• Long-acting reversible contraception (LARC) — IUDs, the implant and the injection, which last from months to years.
• Emergency contraception — a backup after unprotected sex, not a regular method.

Barrier methods work by stopping sperm from reaching an egg. Condoms have an extra benefit: they are the only contraception that also lowers the chance of passing on an STI. If STIs are a concern, or you have a new partner, it is worth using a condom as well as your main method.

An external condom is a thin sheath, usually latex (latex-free options exist for allergies), worn over the penis during sex. It is used once and thrown away, and can be bought cheaply from supermarkets and pharmacies without a prescription. As well as preventing pregnancy, condoms lower the risk of many STIs.

External condoms are about 98% effective with perfect use, and about 87% with typical use. They are more likely to fail if they are past their expiry date, the wrong size, torn, or stored somewhere hot for a long time.

There are usually no side effects, though some people are sensitive to latex — a latex-free condom can be used instead.

An internal condom is a soft pouch put inside the vagina before sex. It works much like an external condom and also lowers the risk of many STIs. It can be inserted a few hours beforehand. Internal condoms are harder to find in Australian shops and cost more than external condoms.

Internal condoms are about 95% effective with perfect use, and about 79% with typical use. They can fail if torn, out of date, or not inserted correctly.

A diaphragm is a soft, shallow silicone cup that covers the cervix so sperm cannot get into the uterus. In Australia there is one size, sold as Caya, used with a lactic-acid gel (Caya Gel). It can be bought without a prescription from some pharmacies, family planning clinics and online, and reused for up to two years. A diaphragm does not protect against STIs, so use a condom as well if that is a concern.

Put about a teaspoon of gel in the cup, then place the diaphragm inside the vagina so it covers the cervix. It can go in up to two hours before sex and must stay in for at least six hours afterwards, but no longer than 24 hours. Before relying on it, ask a doctor or nurse to check it fits and that you are using it correctly — it does not fit about one in seven people correctly.

The diaphragm is about 86% effective with perfect use, and about 82% with typical use. It is less reliable if it does not fit well, is put in wrongly, is taken out too soon, is torn or out of date, or is used without the gel.

Side effects are uncommon. Some people get more bladder infections when using a diaphragm, and very rarely it has been linked to a serious infection called toxic shock syndrome.

These are short-acting hormonal methods: they work well but rely on you using them regularly. None of them protect against STIs, so use condoms with new partners.

The combined oral contraceptive pill (often just “the pill”) is a daily tablet containing two hormones, oestrogen and progestogen. It needs a prescription. It usually comes in 28-day packs with three weeks of hormone pills and one week of inactive (“sugar”) pills. In that week you have a bleed. You can skip the inactive pills and go straight to the next pack to skip that bleed. The pill is also used to help with heavy, painful or irregular periods — see menstrual disorders.

It mainly stops the ovaries releasing an egg. It also thickens the mucus at the cervix, which makes it harder for sperm to get through.

Brands vary, so side effects differ from person to person. Common ones include nausea, headaches, tender breasts, mood changes, skin changes and some irregular bleeding, and many settle within a few months. Contact your doctor if side effects persist.

The combined pill is not suitable for everyone — for example, some people cannot take oestrogen. Dr Mahadik will go through your health history to check it is a safe choice for you.

The combined pill is over 99% effective with perfect use, and about 93% with typical use. A few things can make it work less well: a missed pill, being sick or having diarrhoea (so your body cannot take it in properly), or some other medicines and supplements such as St John’s Wort. Ask your doctor or pharmacist if anything you take could affect it.

Take it as soon as you remember, even if that means two pills in one day. Depending on how many you have missed and where you are in your cycle, you may need backup contraception and possibly emergency contraception. The leaflet in your pack has specific instructions, and your pharmacist can help.

Your fertility usually returns within one to three months of stopping the pill. If you are planning a pregnancy, see planning your pregnancy.

The mini-pill contains just one hormone, progestogen. It can be used while breastfeeding and by many people who cannot take oestrogen. It needs a prescription and comes in 28-day packs of hormone pills only (no inactive pills). Timing matters more than with the combined pill.

It mainly thickens the mucus at the cervix so sperm cannot get through, and sometimes also stops the ovaries releasing an egg.

Common side effects include irregular bleeding, headaches, tender breasts, mood changes and skin changes, many of which settle with time. It may not suit you if you have severe liver disease or have been treated for breast cancer — Dr Mahadik can talk this through with you.

The mini-pill is over 99% effective with perfect use, and about 93% with typical use. Some older mini-pills must be taken within the same three-hour window each day. A newer type has a wider window. A few things can make it work less well: taking it late, being sick or having diarrhoea, or some other medicines. If you miss one, take it as soon as you remember and use condoms for the next few days. If you have had unprotected sex, consider emergency contraception.

The vaginal ring (sold as NuvaRing in Australia) is a soft plastic ring that you place in the vagina yourself. It releases oestrogen and progestogen, the same hormones as the combined pill. You leave it in for three weeks, then take it out for one week — when you have a bleed — before putting a new one in. It needs a prescription.

Like the combined pill, it stops the ovaries releasing an egg and thickens the mucus at the cervix. Because you replace it monthly rather than daily, there is less to remember.

The vaginal ring is over 99% effective with perfect use, and about 93% with typical use. A few things can make it work less well: putting a new ring in late, using it incorrectly, or some other medicines.

Long-acting reversible contraception (LARC) suits people who would rather not think about contraception every day. These methods last from a few months to several years, work whether or not you remember anything day to day, and can be removed when you want to try for a pregnancy. They are among the most reliable methods because there is little that can go wrong once they are in place.

An IUD is a small T-shaped device placed inside the uterus. There are two kinds in Australia — hormonal and copper. Both have fine threads that sit at the top of the vagina (you cannot see them from outside) so the device can be checked and later removed. You need a prescription, and a trained doctor inserts it. Neither IUD protects against STIs.

The hormonal IUD slowly releases progestogen into the uterus. This thickens the mucus at the cervix, thins the lining of the uterus, and sometimes stops the ovaries releasing an egg. There are two brands: Mirena, which lasts up to 8 years, and Kyleena, which is slightly smaller, has a lower dose and lasts up to 5 years. Many people have much lighter periods or none at all, which is why the hormonal IUD is also used to treat heavy periods and as part of menopause care — see menopause.

The copper IUD releases a small amount of copper, which stops sperm and egg from meeting and changes the lining of the uterus. It contains no hormones and lasts between 5 and 10 years depending on the type. Periods can be heavier or more crampy, especially at first. The copper IUD can also be used as emergency contraception.

An IUD can often be inserted in the rooms without a general anaesthetic. If you have not had children, or have a tight cervix, it may be done under general anaesthetic so it is more comfortable. Removal is usually straightforward and done in the rooms.

Cramping for a few days after insertion is common, and spotting or more frequent bleeding can last for the first few months. With the hormonal IUD, periods usually become lighter over time and some people also get headaches, tender breasts, mood or skin changes early on, which generally settle. With the copper IUD, periods may stay heavier. Very rarely, insertion can cause a small hole in the uterus or an infection. If you fell pregnant with an IUD in place, there is a small chance of an ectopic pregnancy. If you think your IUD has moved, use condoms and have it checked.

Both IUDs are over 99% effective, with almost no difference between perfect and typical use because there is nothing to remember day to day. TThe hormonal IUD starts working straight away if put in during the first 7 days of your cycle. Otherwise it works after 7 days. The copper IUD works immediately. An IUD becomes less reliable if it falls out, sits in the wrong position, or is left in past its replacement date. Fertility returns quickly after removal — you can become pregnant before your next period.

The implant (Implanon NXT in Australia) is a soft plastic rod about 4 cm long, placed just under the skin of the inner upper arm. It releases progestogen, which stops the ovaries releasing an egg and thickens the mucus at the cervix. It needs a prescription and is inserted by a trained doctor using local anaesthetic. It lasts for 3 years and can be removed sooner if you wish.

Bleeding patterns change: periods may become lighter, stop, or be irregular or prolonged; the pattern in the first three months is usually a good guide to what follows. Other possible side effects include headaches, bloating, tender breasts, mood changes and skin changes, which often settle. Medicine can sometimes help with troublesome bleeding.

The implant is over 99% effective, with little difference between perfect and typical use. It takes about 7 days to start working if put in outside the first days of your cycle, so use backup contraception in that time. A trained clinician removes it, and fertility returns quickly afterwards.

Depo-Provera is an injection of progestogen given every 12 to 14 weeks, usually into the upper arm or buttock. You get a prescription, collect it from the pharmacy, and return to have it given. It stops the ovaries releasing an egg and thickens the mucus at the cervix. It does not protect against STIs.

Weight gain is a common side effect. Bleeding patterns change. Many people have no periods after a while. Others have irregular or prolonged bleeding, which usually improves, and medicine can help. Other possible side effects include mood changes, headaches, bloating, tender breasts and skin changes. It can cause a temporary drop in bone strength, which usually returns to normal after you stop the injection. It may not suit you if you have severe liver disease or have been treated for breast cancer, and it is less ideal if you want to conceive in the near future.

The injection is over 99% effective with perfect use, and about 94% with typical use; it is less reliable if given late. After the first injection it takes about 7 days to start working, so use backup contraception in that time. Fertility can take longer to return than with other methods — usually between 3 and 18 months after the last injection — so it is not the best choice if you want to conceive soon.

Emergency contraception is a backup after unprotected sex, a missed pill or a split condom. It is not meant as a regular method. There are two options: the morning-after pill and the copper IUD.

There are two types of morning-after pill in Australia: a levonorgestrel (LNG) pill, taken up to 3 days after unprotected sex, and an ulipristal acetate pill (ellaOne), taken up to 5 days after. Both mainly work by delaying the release of an egg. You do not need a prescription — you can buy them from a pharmacy. Take it as soon as you can, because both work better the sooner they are used.

The morning-after pill is estimated to be around 85% effective when taken promptly. It may not work if you take it too late, vomit soon after taking it, or take some other medicines. It can change the timing or heaviness of your next period; if your period is more than 7 days late, take a pregnancy test. Possible side effects include headaches, nausea, bloating and tender breasts. The morning-after pill is not the same as an abortion, and it will not harm an existing pregnancy.

The copper IUD is the most effective form of emergency contraception (over 99%) and can be fitted within 5 days of unprotected sex. It has the added benefit of then providing ongoing contraception for years. It needs to be inserted by a trained clinician.

There is no single method that suits everyone. The right choice depends on your health, your preferences and your plans, and it can change over time. A consultation is the best way to weigh up the options — the notes below cover a few common situations.

If oestrogen is not suitable for you, there are still several options: barrier methods, the mini-pill, the implant, the injection, and both the hormonal and copper IUD.

Breastfeeding can delay your periods returning, but you can still get pregnant, so contraception is still needed. Oestrogen can reduce your milk supply, so oestrogen-free options are usually preferred: condoms, the diaphragm, the mini-pill, the injection, the implant and IUDs.

Only condoms (external and internal) lower the risk of STIs, and even then not completely. Whatever your main method, using condoms with new partners and having regular sexual health checks is wise — see STI testing and treatment.

Some methods are also used to help with medical conditions — for example, the combined pill or hormonal IUD for heavy or painful periods, endometriosis or PMOS. If a condition is part of the picture, Dr Mahadik can suggest a method that helps on both fronts.

Many contraceptives are subsidised through the Pharmaceutical Benefits Scheme (PBS), and a GP referral lets you claim a Medicare rebate on your specialist consultation. Fees and any gap depend on the visit and your cover — for current fees, please contact the rooms.