A to Z of Contraception

Condoms, coils and depo injections. There’s a whole range of options for birth control. Dr Rebecca Daly breaks down all the contraception methods available, how they work, their effectiveness and any possible side effects.


Easily available and hormone free, condoms are an option at all stages of life.  The added benefit being they protect against sexually transmitted infections. However, they can split or come off.  Plus, they are the least reliable of all methods, being only 85% effective at preventing pregnancy.

The “pill”

Still the most popular method, a combined oestrogen and progestogen pill  taken once a day for 3 weeks followed by a week of no pills (or sugar pills). Many women like feeling in control of their contraception with the pill and are reassured by the monthly bleed it brings.

Taken correctly, the pill is a reliable method (91% efficacy) and can make periods lighter and less painful. It also reduces the risk of cancer of the womb, ovary and colon.

It is not suitable if you are over weight, smoke over the age of 35 or suffer from certain types of migraine. There is a small increased risk of thrombosis and breast cancer. More commonly it can cause hormonal side effects such as acne, mood changes, nausea and breast pain.

The “mini pill”

Containing only one hormone (progestogen) the mini pill is 91% effective in preventing pregnancy with typical use and is suitable for women who can not have oestrogen. Hormonal side effects can be problematic and there is no regular monthly bleeding pattern. It can also increase ovarian cysts.

LARC- Coils/Implants/depo injection

Women are increasingly turning to the longer-acting but reversible contraception options, also called LARC. These very reliable methods work for you straight away, so you do not have to remember to take a pill.

Once removed, your fertility comes back quickly (with the exception of the depo injection). The dose of hormone is generally lower too meaning so hormonal side effects may be less. LARC methods are not affected by diarrhoea or vomiting.

All these methods can cause erratic bleeding and spotting, particularly in the first 2-3 months. All LARCs require a fitting procedure which can be done in our IMC clinic.


A T shaped device that is placed in the womb. The copper coil has the advantage of being hormone free, but it can make periods heavier or more painful. The mirena coil has a low dose of progestogen within it and periods often stop in most women after a year.

Both methods are over 99% effective but they require a procedure for fitting that can cause period type cramping and bleeding. Rarely, serious side effects such as perforation of the womb or infection can occur. They last 5-10 years depending on the device used.


A match sized implant placed under the skin in the arm, the implant lasts 3 years and is 99% effective. It requires a small procedure to fit and remove the implant but is less invasive than coil fitting.

Depo injection

Over 95% effective with typical use, the depo injection is a progestogen only hormone given once every 12 weeks. The injection can not be removed from the body once administered so any side effects will have to be tolerated until it wears off. It should be avoided in people at risk of osteoporosis as there is a small risk of a reduction in bone density over time. It can cause weight gain in some women.


Dr Rebecca Daly - Doctor IMC KatongDr Rebecca is a GP at IMC Katong and has developed a keen interest in women’s health, having completed the Diploma of Obstetrics and Gynaecology (UK) in 2006 and the Diploma of Sexual and Reproductive Health (UK) 2009.

She has been a member of the Faculty of Sexual and Reproductive Health for 10 years and is a qualified contraceptive coil and implant fitter.


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