Contraceptive pills and injections

Contraceptive pills and injections use hormones to prevent pregnancy.

Key points about contraceptive pills and injections

  1. Contraceptive pills are available in 2 types – the combined pill and the progestogen-only pill. The contraceptive injection is called Depo Provera.
  2. These contraceptive options are suitable for most people, but you need to remember to take the pill every day at the same time or the injection every 13 weeks.
  3. If you have any medical conditions your doctor or nurse will be able to work out whether a contraceptive pill or injection is safe for you.
  4. Talk to your doctor or nurse if you want to know which is suitable for you.

What are contraceptive pills and injections?

These contraceptive methods prevent pregnancy using hormones. You have to take them regularly for them to work well, which makes them different from the long-acting reversible contraceptives (LARC) which you can “fit and forget” for several years. Read more about LARCs.

  • Contraceptive pills include the combined pill and the progestogen-only pill.
  • The injection is called Depo-Provera, or ‘the Depo’. It is given through a needle into your buttock or upper arm muscle.

Who are contraceptive pills and injections suitable for?

Contraceptive pills and injections are suitable for most people but not everyone. Depending on the type, they may NOT be suitable if you have medical conditions such as:

  • migraines
  • high blood pressure, heart conditions or stroke
  • blood clots in the past, or high risk of blood clots
  • liver disease
  • gallstones
  • diabetes
  • breast cancer.

Some options may also NOT be suitable if:

  • you are overweight with a BMI of more than 35
  • you are aged over 35 years and you smoke
  • you are taking certain medicines, over-the-counter medicines or herbal supplements.

Your doctor or nurse will be able to work out with you which method is safe and suits you best.

What are the pros and cons of contraceptive pills and injections?

Pros Cons

✔ They don't interfere with having sex.

✔ Your periods are likely to be regular, shorter, lighter or you may even have no periods and less painful ones.

✔ The combined pill can significantly reduce the risk of endometrial and ovarian cancer, and also reduces the risk of bowel cancer.

✔ The effectiveness at preventing pregnancy is about 92–99%, depending on whether you are using them regularly.

✘ You need to remember to take the pill every day at the same time or the injection every 13 weeks.

✘ You may have irregular bleeding when you first start using hormonal contraception.

✘ The combined pill will very slightly increase your risk of blood clots, cervical cancer and breast cancer during the time you are taking it.

✘ They do not protect you from sexually transmitted infections (STIs) – you need to use condoms as well to protect you from STIs. Read more about STIs and safer sex.

 

 

What is the contraceptive pill?

There are 2 types of oral contraception available in New Zealand. These are:

  • the combined pill, known as ‘the pill’, which contains the hormones oestrogen and progestogen
  • the progestogen-only pill, which contains only progestogen.

Combined pill ('the pill')

The combined pill contains the female hormones oestrogen and progestogen. It works by stopping your ovaries from releasing an egg each month. The combined pill makes periods more regular and lighter, so it is also used to treat heavy or painful periods.

Most people can take the combined pill. However, it may not be suitable if you have some medical conditions. Talk to your doctor or nurse to see if it is suitable for you.

The combined pill needs to be taken every day, but many people do forget one from time to time, so in real-life usage it has an average failure rate of 8% compared with a failure rate of 1% if taken every day.

Chance of getting pregnant: 1–8%. 

This means that for every 100 people taking the combined pill for 1 year, there would be between 1 and 8 pregnancies. 

Read more about the combined pill

Progestogen-only pill

The progestogen-only pill works by making your cervical mucus thicker and changing the lining of your womb. This makes it less likely that a sperm fertilises an egg and if an egg is fertilised it less likely to bury itself in your womb to grow. Cerazette is a progestogen-only pill which also stops your ovaries releasing an egg each month.

The progestogen-only pill is safer than the combined pill for some people with medical conditions and has no risk of blood clots. However, it may cause irregular bleeding and it has to be taken at exactly the same time each day which some people find difficult. It can be used while you are breastfeeding. 

Chance of getting pregnant: 1–8%.

R
eal-life usage has an average failure rate of 8% compared with a failure rate of 1% if taken at exactly the same time every day. This means that for every 100 people taking the combined pill for 1 year, there would be between 1 and 8 pregnancies.

Read more about the progestogen-only pill.

What is Depo-Provera?

The common side effects include irregular bleeding, no periods or a change in weight. It may take up to 1 year for your periods and fertility to return after stopping this method.

Chance of getting pregnant: 1–6%.

This means that for every 100 people using the injection for 1 year, there would be between 1 and 6 pregnancies. 
Read more about Depo-Provera.

Learn more

The following links provide further information about hormonal contraception. Be aware that websites from other countries may have information that differs from New Zealand recommendations.   

Combined oral contraceptive pill Family Planning, NZ
Progestogen-only contraceptive pill Family Planning, NZ
Depo Provera injection Family Planning, NZ
Combined hormonal contraceptives Patient Info, UK
The combined oral contraceptive (COC) pill Patient Info, UK
Combined pill NHS, UK

References

  1. New Zealand Aotearoa’s guidance on contraception Ministry of Health, NZ, 2020
  2. Oral contraceptives: selecting a pill BPAC, NZ, 2019

Reviewed by

Dr Alice Miller trained as a GP in the UK and has been working in New Zealand since 2013. She has undertaken extra study in diabetes, sexual and reproductive healthcare, and skin cancer medicine. Alice has a special interest in preventative health and self-care, which she is building on by studying for the Diploma of Public Health with the University of Otago in Wellington.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Alice Miller, FRNZCGP, Wellington Last reviewed: 24 Mar 2021