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How effective is your contraception?

Tuesday, April 1, 2014


We celebrate World Health Day on 7 April.

Being able to control if and when you have children is a big part of maintaining your health. So is choosing the right contraceptive method for you.

This month we compare the effectiveness of different contraceptive methods in preventing pregnancy. Different methods suit different people according to their age, life stage, finances and personality.

With no method of contraception, 85% of women in their 20s will become pregnant within one year.

We specifically look at effectiveness of preventing pregnancy here. Only condoms and diaphragms provide protection against both pregnancy and STIs.

Image source: Trussell J, Guthrie KA. Choosing a contraceptive: efficacy, safety, and personal considerations. In: Hatcher RA, Trussell J, Nelson AL, Cates W, Kowhal D, Policar M (eds). Contraceptive Technology: Twentieth Revised Edition. New York NY: Ardent Media; 2011. p. 45-74.

Perfect use vs typical use

Many contraceptive methods are affected by human error such as forgetting to take your pill. They may be very effective with “perfect use” but the effectiveness of certain methods as “typically used” is likely to be lower.

Perfect use of a contraceptive method is when it is used correctly all the time.

Typical use is what generally happens in real life. It takes into account human error.

As you can see below, for long acting reversible contraception (LARCs) the perfect use is the same as typical use. This is because you don’t have to remember to take anything or get the condom on correctly. This is why more and more women are choosing LARCs.

Effectiveness of different contraception methods
Contraception effectiveness is measured by how many women will get pregnant within a year of using that method.

For example, the effectiveness of male condoms with perfect use is 98%. This means out of 100 women using condoms correctly all the time, two will become pregnant within one year.

Sometimes the effectiveness is quoted for the first year of use when people are learning how to use a method correctly. These figures below quote the first year use.

Barrier Methods

Male Condoms

  • Perfect use: 98% effective
  • Typical use: 85% effective


  • Perfect use: 94% effective
  • Typical use: 84% effective

Oral Contraceptive Pill

Combined oral contraceptive, aka The Pill

  • Perfect use: over 99% effective
  • Typical use: 92% effective

Taking the pill continuously (i.e. skipping your period) is likely to be safer.

Progestogen-only pills, aka The Minipill

  • Perfect use: over 99% effective
  • Typical use: 92% effective

Long-Acting Reversible Contraception Methods (LARCs)


  • Perfect use: over 99% effective
  • Typical use: over 99% effective

Copper IUD

  • Perfect use: over 99% effective
  • Typical use: over 99% effective


  • Perfect use: over 99% effective
  • Typical use: over 99% effective


  • Perfect use: over 99% effective
  • Typical use: over 99% effective


Depo Provera Injection

  • Perfect use: over 99% effective
  • Typical use: 97% effective

Nuva Ring

  • Perfect use: over 99% effective
  • Typical use: 92% effective

Emergency Contraception

Emergency contraception pill (ECP)

  • Within 4 days of unprotected sex: 98-99% effective
  • After 4 days: not effective

Research shows the ECP may not work for women with a BMI over 30. The copper IUD is a good option for these women.

Copper IUD

  • Within 5 days (120 hours) of unprotected sex: over 99% effective
  • After 5 days: not effective



  • Failure rate: 1 in 1,000 (after waiting for two sperm-free semen tests)

Tubal ligation

  • Failure rate: 1 in 200
Some information sourced from Contraception: your questions answered. 6th edition, 2013. Guillebaud J, MacGregor A. Churchill Livingstone Elsevier.

Family Planning has clinics located throughout New Zealand. Use the clinic finder to find your nearest clinic.

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