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Patient education: Emergency contraception (Beyond the Basics)

Patient education: Emergency contraception (Beyond the Basics)
Literature review current through: May 2024.
This topic last updated: Apr 25, 2023.

INTRODUCTION — Emergency contraception is a way to lower the risk of pregnancy after unprotected sex. It does not end a pregnancy that has already started.

Emergency contraception is intended for occasional use, not as a primary form of birth control. More information about different birth control options is available separately. (See "Patient education: Birth control; which method is right for me? (Beyond the Basics)" and "Patient education: Hormonal methods of birth control (Beyond the Basics)" and "Patient education: Barrier and pericoital methods of birth control (Beyond the Basics)" and "Patient education: Long-acting methods of birth control (Beyond the Basics)".)

WHEN TO USE EMERGENCY CONTRACEPTION — You might choose emergency contraception if:

You had unprotected vaginal sex any time within the last five days (120 hours).

You used your regular method of birth control incorrectly, or your regular method of birth control might have failed within the last five days (120 hours). Reasons why a regular method of birth control could fail include:

A condom breaks, slips off, or is not used the whole time you are having sex.

You normally take birth control pills containing both estrogen and progestin but forgot to take your pills two or more days in a row.

You normally take birth control pills containing just progestin (called the "minipill") and took your pill more than three hours late.

You normally use injections of depot-medroxyprogesterone acetate (brand name: Depo-Provera) but are more than two weeks late for your injection (some providers recommend emergency contraception only if you are more than four weeks late).

A diaphragm or cervical cap moves, breaks, tears, or is removed too soon.

A birth control skin patch comes off, is removed too early, or is put on too late.

A birth control vaginal ring comes out, is removed too early, or is inserted too late.

Your partner does not "pull out" or withdraw in time and ejaculates inside your vagina or on your genitals.

A spermicidal (sperm-killing) tablet or film fails to melt before sex.

You use the "rhythm method" and made a mistake figuring out the "safe time" in your cycle, or you have sex during your "fertile window" (days when you are more likely to conceive).

An intrauterine device (IUD) accidentally comes out.

Emergency contraception can also be used after sexual assault, in cases when a person was forced to have unprotected sex against their will. (See "Patient education: Care after sexual assault (Beyond the Basics)".)

Is emergency contraception safe? — Yes, the different types of emergency contraception are safe in most people. IUDs can be used by most people. The pills used in hormonal emergency contraception contain the same hormones found in hormonal birth control methods (birth control pills, skin patches, vaginal rings, and certain IUDs). These hormones have been used safely for years.

Even people who cannot use estrogen-containing hormonal birth control as their primary method of contraception (such as those age >35 years who smoke or those with a history of heart attack, stroke, clotting disorders, migraine headaches, or liver disease, or who are breastfeeding) can use emergency contraception because the hormones are taken for only one day.

Some types of emergency contraception do not contain any hormones. These types are the copper IUD and a pill containing ulipristal acetate.

HOW EMERGENCY CONTRACEPTION WORKS — The main way that emergency contraception pills work is by preventing ovulation (release of the egg from the ovary). Ulipristal acetate (ella) does this a little later in the menstrual cycle (closer to the time of ovulation) compared with oral levonorgestrel (Plan B); this may explain its slightly higher efficacy. (See 'How well does emergency contraception work?' below.)

All methods of emergency contraception work by reducing the chance that an egg will be fertilized by sperm. Intrauterine devices (IUDs), and to a lesser extent ulipristal acetate, may also reduce the chance that a fertilized egg will implant and begin a pregnancy.

Emergency contraception cannot reverse a pregnancy that has already started. In other words, if a fertilized egg has already implanted itself in the uterus, emergency contraception will not interfere with or harm the pregnancy. Emergency contraception is not the same as medication abortion (sometimes called the "abortion pill"), which contains different medications.

TYPES OF EMERGENCY CONTRACEPTION — There are two main types of emergency contraception, and each is discussed below.

IUD — An intrauterine device (IUD) can also be used for emergency contraception. There are two types of IUDs:

Copper-containing IUD (brand name: Paragard).

IUDs that release the hormone progestin (this only applies to IUDs that contain 52 mg of levonorgestrel; brand names: Mirena, Liletta).

An IUD must be inserted into the uterus by a health care provider. While IUDs are much more effective at preventing pregnancy than the pill methods, they do require an office visit and may be more costly in the short-term. They are a good choice for people who want an ongoing method of birth control. (See "Patient education: Long-acting methods of birth control (Beyond the Basics)".)

Pills — Oral emergency contraception involves the use of pills that either contain hormones or interfere with hormones.

Ulipristal acetate — Ulipristal acetate (brand name: ella, ellaOne) is not a hormone, but it works by preventing the hormone progesterone from having its normal effect on ovulation and the inside of the uterus. Ulipristal acetate comes in a single-dose pill and is available only by prescription.

Levonorgestrel — Levonorgestrel is a synthetic hormone. This type of emergency contraception (sample brand names: Plan B One-Step, Next Choice One Dose) is available without a prescription at many drug stores and at clinics like Planned Parenthood. Levonorgestrel can be given as one pill or two, depending on the dose. Which type is available depends on where you are. Be sure to read the instructions carefully to make sure you know how many pills to take and when.

Mifepristone — This medication is available for emergency contraception in some countries, although not in the United States. The dose used for emergency contraception is much lower than that used for medication abortion (eg, 10 mg versus 200 mg).

Birth control pills — Regular birth control pills can also be used as emergency contraception. This does not work as well as the other methods and is more likely to cause nausea (see 'Side effects of emergency contraception' below), but it might be a good option in some situations.

If you use birth control pills for emergency contraception, you have to take more than one pill at a time, and a second dose 12 hours after the first. The table tells you which birth control pills you can use for emergency contraception, which color pills to take, and how many (table 1). Birth control pills require a prescription in the United States. Talk to your health care provider to make sure you are taking the correct pills and dose.

HOW WELL DOES EMERGENCY CONTRACEPTION WORK? — Intrauterine devices (IUDs) are more effective than pills, and the copper IUD is the most effective form of emergency contraception. Both the copper and hormonal IUDs prevent more than 99 percent of pregnancies when inserted within five days of unprotected sex. If you weigh 165 pounds (75 kilograms) or more, you might want to consider an IUD instead of pills. Both types of IUDs work very well to prevent pregnancy regardless of body weight.

If you choose pills for emergency contraception, several different things can affect how well they work, including how soon you take the pills after sex, where you are in your menstrual cycle, how many times you had unprotected sex, and how much you weigh. In general, the sooner you take the pills after unprotected sex, the better they work. When used within three days (72 hours) of unprotected sex:

Ulipristal acetate – After taking ulipristal acetate (brand name: ella, ellaOne), the risk of pregnancy is 1 to 2 percent. This means that 1 to 2 people out of 100 who use this type will get pregnant anyway.

Levonorgestrel – After taking levonorgestrel (sample brand names: Plan B One-Step, Next Choice One Dose), the risk of pregnancy ranges from 1 to 7 percent. This means that 1 to 7 people out of 100 who use this type will get pregnant anyway.

Mifepristone – Mifepristone is as effective as levonorgestrel in preventing pregnancy. This method is only available in select countries and is not available in the United States.

Birth control pills – Taking a combination of birth control pills will lower the risk of pregnancy, but it is less effective than other methods.

WHERE TO GET EMERGENCY CONTRACEPTION

Over-the-counter — In the United States, you can buy levonorgestrel (sample brand names: Plan B One-Step, Next Choice One Dose) without a prescription from a pharmacy or clinic. A person of any age can purchase levonorgestrel, and you do not need to show an ID.

Even though emergency contraception may be available without a prescription, it is not always easy to get to a pharmacy when you need to take the pills. Also, not all pharmacies carry the medications or make them easily available on the shelf. As a result, if you choose not to get an intrauterine device (IUD) or another long-term form of birth control, it is a good idea to buy emergency contraception pills to keep on hand in case you need them in the future. If you do this, check periodically to make sure the medication has not expired.

Prescription required — Ulipristal acetate (brand names: ella, ellaOne) and standard birth control pills (estrogen and progestin) require a prescription, regardless of age. An IUD must be placed by a health care provider.

Online access — If you need emergency contraception, it is a good idea to talk with your health care provider about your options, if possible. However, in some areas, you can get emergency contraception (including ulipristal acetate and levonorgestrel) through online services such as PRJKT RUBY (www.prjktruby.com/emergency-contraception) and Nurx (www.nurx.com).

HOW TO TAKE EMERGENCY CONTRACEPTION — You do not need to have a physical examination or any laboratory tests to take over-the-counter emergency contraception. However, if you need emergency contraception because you were sexually assaulted, you should seek the help of a counselor or other health care professional. A doctor should rule out pregnancy by taking your medical history, doing a physical examination, and/or ordering laboratory testing before giving you a prescription for emergency contraception. (See "Patient education: Care after sexual assault (Beyond the Basics)".)

Timing — You can take emergency contraception pills any time during your menstrual cycle. It does not matter when you had your last period.

Ulipristal acetate is effective up to five days (120 hours) after unprotected sex.

Both the levonorgestrel pills and estrogen-progestin pills are most effective when taken as soon as possible after unprotected sex, ideally within three days (72 hours). You can take them up to five days (120 hours) after sex, although they become less effective as more time goes by.

The intrauterine device (IUD) can also be inserted up to five days (120 hours) after unprotected sex, and is possibly as effective if inserted beyond this time period.

Emergency contraception medication and dose

IUD — The best way to prevent pregnancy after unprotected sex is to have an IUD inserted. While there are over 35 studies showing that the copper IUD is the most effective method for emergency contraception, a new study showed that the hormonal IUD is also highly effective. This is a good choice if you would like to leave the IUD in place and use it as your ongoing method of birth control. IUDs are discussed in detail separately. (See "Patient education: Long-acting methods of birth control (Beyond the Basics)".)

Levonorgestrel — Levonorgestrel is a hormone. This type of emergency contraception (sample brand names: Plan B One-Step, Next Choice One Dose) is available without a prescription at many drug stores and at clinics like Planned Parenthood. Depending on the brand and dose, you might need to take one pill or two. Be sure to read the instructions carefully to make sure you know how many pills to take and when.

Ulipristal acetate — Ulipristal acetate comes (by prescription) in the form of a single 30 mg tablet.

Birth control pills — No estrogen-progestin pill is available in pill packets specifically for emergency contraception. However, many birth control pills contain these two hormones. The table provides information on which birth control pills you can take as emergency contraception and how many pills to take for each dose (table 1).

Side effects of emergency contraception — Nausea and vomiting are the most common side effects of emergency contraception pills. This is more likely with birth control pills than with ulipristal acetate and levonorgestrel. The IUDs can cause cramping and spotting at the time of insertion. These symptoms are usually mild and go away in one or two days.

Preventing nausea and vomiting — If you are worried about developing nausea and vomiting, you can take a medication to prevent these side effects:

Meclizine (sample brand names: Antivert, Bonine, Dramamine) is a nonprescription medication that helps prevent nausea and vomiting. If you use one of these medications, be sure to follow the dosing instructions on the box or bottle.

Metoclopramide (brand name: Reglan) is another medication that helps prevent nausea and vomiting, but you will need to get a prescription for it from your health care provider.

What to do if you vomit — If you throw up less than one hour after taking birth control pills for emergency contraception, you will need to take them again.

WHAT TO EXPECT AFTER TAKING EMERGENCY CONTRACEPTION

When will I get my period again? — You should get your period within about one week of when you would normally expect it. If you took ulipristal acetate, do not be surprised if your period is a few days late; this is normal. But, if you do not have a normal period within three or four weeks, no matter which form of emergency contraception you took, you should take a home pregnancy test. If the test is negative, wait for your period for one more week. If you still have not had a period by this time, call your health care provider for further instructions. If the test is positive and you are pregnant, your provider can talk to you about your options and what to do next. If you are bleeding more than a normal period or have abdominal pain in your belly, you should also see your provider.

Birth control — If you have unprotected sex again after you take emergency contraception pills, you could get pregnant. Be sure to use some form of birth control until you get your period. The highest risk of pregnancy is for people who have additional unprotected sex in the same month after using oral emergency contraception pills. This is not an issue if you had an intrauterine device (IUD) inserted for emergency contraception, as it will provide ongoing birth control for as long as you have it in.

If you normally use birth control pills, a patch, or a vaginal ring, but you missed some doses, you should resume those methods the day after taking emergency contraception, although you will need to use a backup form of birth control (such as condoms) for at least seven days. However, if you took ulipristal acetate and you normally use birth control pills, wait at least five days before starting your regular pills again if you missed more than two days of pills. This is because ulipristal acetate can interfere with the way birth control pills work. If you missed only one or two days, then restart your birth control pills right away. Even after you start taking your pills again, you should still use a condom every time you have sex until your next period. (See "Patient education: Hormonal methods of birth control (Beyond the Basics)".)

If you normally use condoms, a diaphragm, or a cervical cap, go back to using those methods right away. (See "Patient education: Barrier and pericoital methods of birth control (Beyond the Basics)".)

If you have unprotected sex again, you can take emergency contraception again.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Emergency contraception (The Basics)
Patient education: Care after sexual assault (The Basics)
Patient education: Hormonal birth control (The Basics)
Patient education: Barrier methods of birth control (The Basics)
Patient education: Intrauterine devices (IUDs) (The Basics)
Patient education: IUD insertion (The Basics)
Patient education: IUD removal (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Barrier and pericoital methods of birth control (Beyond the Basics)
Patient education: Hormonal methods of birth control (Beyond the Basics)
Patient education: Long-acting methods of birth control (Beyond the Basics)
Patient education: Permanent birth control for females (Beyond the Basics)
Patient education: Vasectomy (Beyond the Basics)
Patient education: Care after sexual assault (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Intrauterine contraception: Candidates and device selection
Contraception: Issues specific to adolescents
Emergency contraception
Evaluation and management of adult and adolescent sexual assault victims in the emergency department

The following organizations also provide reliable health information.

National Library of Medicine

(https://medlineplus.gov/healthtopics.html)

National Institute of Child Health and Human Development (NICHD)

Toll-free: (800) 370-2943

(www.nichd.nih.gov)

National Women's Health Resource Center (NWHRC)

Toll-free: (877) 986-9472

(www.healthywomen.org)

Planned Parenthood Federation of America

Phone: (212) 541-7800

(www.plannedparenthood.org)

The Hormone Foundation

(www.hormone.org)

Disclaimer: This generalized information is a limited summary of diagnosis, treatment, and/or medication information. It is not meant to be comprehensive and should be used as a tool to help the user understand and/or assess potential diagnostic and treatment options. It does NOT include all information about conditions, treatments, medications, side effects, or risks that may apply to a specific patient. It is not intended to be medical advice or a substitute for the medical advice, diagnosis, or treatment of a health care provider based on the health care provider's examination and assessment of a patient's specific and unique circumstances. Patients must speak with a health care provider for complete information about their health, medical questions, and treatment options, including any risks or benefits regarding use of medications. This information does not endorse any treatments or medications as safe, effective, or approved for treating a specific patient. UpToDate, Inc. and its affiliates disclaim any warranty or liability relating to this information or the use thereof. The use of this information is governed by the Terms of Use, available at https://www.wolterskluwer.com/en/know/clinical-effectiveness-terms. 2024© UpToDate, Inc. and its affiliates and/or licensors. All rights reserved.
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