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Choosing the right emergency contraception

Sunday, July 16, 2017


If you forgot to use contraception the last time you had sex, or you did but it failed, you might need emergency contraception.

When you talk to a nurse, doctor or pharmacist about getting emergency contraception, there are a few important questions they will ask you, including how long ago you had unprotected sex and your weight.

These may seem like personal questions, but they’ll help make sure you get the emergency contraception that works for you, either the emergency contraceptive pill (ECP) or a copper intra-uterine device (IUD). 

The most effective emergency contraceptive is the IUD but the ECP can be effective in many situations.


Up to 3 days after unprotected sex

The emergency contraceptive pill (ECP) is approved to be taken up to 3 days (72 hours) after sex, however new research shows it is just as effective up to four days after sex.

The ECP is 98% effective.

Up to 5 days after unprotected sex

A copper IUD can be inserted into the uterus up to five days after the egg could have been fertilised.  To work this out, the nurse or pharmacist might ask when your last period was and how long your cycles are.

The copper IUD is more than 99% effective and it will provide contraception for five to ten years.


If you weigh under 70kg, the ECP is 98% effective at preventing pregnancy.

If you weigh 70kg or more, or have a BMI of 26 or more, the ECP can be less effective and there will be a bigger risk that it won’t work.

Doubling-up and taking two ECPs might make it more effective, but we don’t have proof that it will work, so getting a copper IUD is the best option.

We recommend the copper IUD if:

  • You want the most effective emergency contraception
  • You weren’t able to get the ECP within 3 days
  • You weigh over 70kg

Your nurse, doctor or pharmacist will explain this all to you, but if you still have any questions, just ask!

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

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