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Emergency contraception: Preventing pregnancy after you have had sex

Highlights
  • An ECP is best used within 3 days (72 hours) of unprotected sex.
  • The sooner you take the ECP, the better it will work.
  • Plan B is now available without a prescription across Canada.
  • The World Health Organization states that ECPs can be safely used to prevent pregnancy.

You can become pregnant if you have unprotected sexual intercourse even just once. Emergency contraception (EC) can prevent pregnancy if you have had unprotected sexual intercourse. However, it should only be used in an emergency situation. If you are sexually active, talk to a doctor or nurse about which birth control method is right for you.

When should I use the emergency contraceptive pill (ECP)?

An ECP is best used within 3 days (72 hours) of unprotected sex. Some doctors or nurse practitioners will prescribe it up to 5 days after unprotected sex, but there is less information about how well it works then. Although sometimes called the morning-after pill, it does not have to be taken in the morning or the “morning-after” unprotected sexual intercourse. The sooner you take the ECP, the better it will work.

Situations where an ECP can be used include:

  • You have had unprotected sex. This means that either no birth control was used or it didn’t work for one of the following reasons:
    • The condom broke, leaked or slipped.
    • You missed more than 2 birth control pills (“the pill”) in a row or you started the pills more than 2 days late.
    • You missed one or more progesterone-only contraceptive pills.
    • You were 2 or more weeks late for your birth control shot or needle, commonly known as Depo-Provera.
    • The birth control patch came off for 24 hours or longer during the “patch-on” weeks.
    • The birth control patch was on for more than 9 days straight.
    • You were more than 2 days late putting the patch back on after the “patch-off” week.
    • Your vaginal ring came out or was removed for 3 hours or longer during the “ring-use” weeks.
    • Your vaginal ring was left in for more than 5 weeks in a row.
    • You were more than 2 days late putting your vaginal ring back in after “ring-out” week.
    • You are concerned that the contraceptive devices such as a diaphragm, cervical cap, vaginal ring, or patch may have slipped, came off, tore or were taken out/off too early. If this is the case, contact your doctor or nurse.
  • You do not remember having sexual intercourse or using contraception.
  • You have been abused, sexually assaulted or raped and are not using a reliable method of birth control.

How well does the ECP work?

If 100 women (who are not using any birth control) have unprotected sex just once, 8 will get pregnant. Using the ECP, between 1 and 3 young woman will get pregnant.
ECPs are only for emergencies. They are not a good form of regular birth control. Things that work better include:

  • birth control pills,
  • the Depo-Provera (the shot or needle)
  • an intrauterine device (IUD), or
  • condoms, ideally with another method of contraception
  • the vaginal ring
  • the birth control patch

In addition these methods, you should use condoms every time you have sex. This is the only way to prevent the spread of sexually transmitted infections (STIs), including HIV, apart from abstinence (not having sex).

The ECP won’t protect you against STIs. If you are worried about STIs, speak to your doctor or visit a clinic.

What are ECPs?

ECPs are made of the same hormones as birth control pills. Some have only one hormone called progestin (commonly know as Plan B) and some have 2 hormones, called estrogen and progestin (known as the Yuzpe method). See Table 1 to see how the methods compare.

Where do I get ECPs?

Plan B is now available without a prescription across Canada through:

  • your doctor,
  • your nurse practitioner,
  • health centre,
  • walk-in clinic,
  • birth control/sexual health clinic, or
  • pharmacist.

Table 1

Yuzpe Method Plan B
Chance of getting pregnant cut by 75%
More nausea and vomiting
Prescription is needed
Costs about $15 to $20
Chance of getting pregnant cut by 85%
Less nausea and vomiting
Available without a prescription
Costs about $20 to $25

Are ECPs safe?

Yes. The amount of hormones in ECPs is low.

The World Health Organization states that ECPs can be safely used to prevent pregnancy.

If you have ever had blood clots, a stroke or a heart attack, you should only use the ECP called Plan B. It is made with only one hormone, progestin.

What if I am already pregnant?

The ECP prevents pregnancy after you have had unprotected intercourse. If you are already pregnant, it will not make your pregnancy go away. It is not an abortion pill. However, if you find out after you have taken it that you are pregnant, it will not harm the fetus. Many women have taken estrogen and progesterone (the hormones in ECPs called Yuzpe) in early pregnancy and have had healthy babies. If you are pregnant, you should discuss your options with a doctor or nurse as soon as possible.

What are the side effects of emergency contraception?

The most common side effects of ECPs are nausea and vomiting, especially with the Yuzpe method. If your doctor gives you this form of ECP, they will also give you medication to prevent vomiting. If you “throw up” within an hour of taking the first dose, you need to take more. Some women also have tender breasts, bloating, irregular bleeding, and headaches. These symptoms do not last long.

How do I use the ECP?

Either kind of ECP (Plan B or Yuzpe) comes in 2 doses. Either method should be taken as soon as possible. For Plan B, taking 2 pills at one time is as effective as the old regimen of taking one pill as soon as possible and then another 12 hours later. For the Yuzpe method, take the first one as soon as possible. Take the second pill 12 hours later.

The first dose or the complete dose for Plan B must be taken within 72 hours (3 days) after unprotected sex. Some doctors or nurse practitioners will prescribe it up to 5 days after unprotected sex, but it is more effective if taken sooner.  The sooner you take the ECP, the better it will work.

If you throw up within 1 hour of taking the pills, you need to take another dose.

If you are given a pill to prevent nausea (routinely given with the Yuzpe method) do not drive or drink any alcohol for 36 hours after the first set of pills. The medication that you take to prevent nausea may make you feel drowsy.

Do not take any extra birth control pills. They will not decrease your chance of getting pregnant and will make you feel sick.

What if it’s too late for the ECP?

If it is too late for you to take an ECP, an IUD may reduce the risk of pregnancy. An IUD may work if you had unprotected sex within the past 7 days. If this is the case, you will have to speak to your doctor or nurse about your options.

What should I do about birth control until my next period?

The ECP is not a method of contraception that will last until your next period. Therefore, it is important for you to discuss other methods of birth control with your doctor or nurse.

If you are already taking birth control pills but have missed some pills, start a new pack of pills the day after you take the ECP. In addition, the use of a condom is essential to prevent STIs.

If you want to start the birth control pill or Depo-Provera (the shot or needle), wait until your next period starts and use condoms and spermicide (like spermicidal cream, jelly or foam) until then.

Your next period may be a little early or a little late. But most women get it at about the regular time. If you don’t have a normal period within 3 weeks of taking the ECP, you should have a pregnancy test to make sure you aren’t pregnant.

Why not just use emergency contraception each time I have sex?

Emergency contraception is not as good at preventing pregnancy as other methods of birth control such as birth control pills taken regularly or Depo-Provera (the shot or needle). In addition, you should always use condoms to prevent STIs.

Where can I find more information?

Your paediatrician, family doctor, pharmacist, nurse or local public health department will have more information about this topic. Remember, Plan B is now available without a prescription across Canada.



Reviewed by the following CPS committees:
Adolescent Health Committee

Last Updated: August 2009