Top things to know about emergency contraception:
Emergency contraceptive pills, hormonal IUDs, the copper IUD, and birth control pills can each be used for emergency contraception
IUDs are the most effective form of emergency contraception
Emergency contraceptive pills are most effective the sooner you take them
If you had unprotected vaginal sex, you could become pregnant. You have up to five days after unprotected sex to use a form of emergency contraception to prevent pregnancy.
You may have heard that emergency contraception shouldn’t be used as birth control. It’s true — other forms of contraception are more effective at preventing pregnancy daily. Emergency contraception would also be more expensive to use than other birth control methods and may have more side effects. But when you need to use emergency contraception, however often you need it, it can help prevent pregnancy.
Emergency contraception works by preventing ovulation, so it will be more effective during some times of the cycle.
In this article, we are going to talk about your different options for emergency contraception. It can be helpful to know your options before you talk to your healthcare provider or pharmacist.
Emergency contraceptive pills (ECPs)
Emergency contraceptive pills (ECPs) are better known as “morning-after pills.” The effectiveness of ECPs primarily depends on where you are in your cycle when you take them — specifically if you take a pill in time to prevent ovulation (4, 5–8). There are two main types of ECPs available in the USA.
Plan B, Next Choice, One Dose, My Way, and Take Action are all the most common types of ECPs: a pill that contains a version of the hormone progesterone, called levonorgestrel. These are available from many pharmacies without a prescription. Levonorgestrel ECPs are taken in a single dose as soon as possible after unprotected sex. While the packages of these pills stipulate that they should be taken within three days (72 hours), their effectiveness may last for at least four days (96 hours), before declining significantly (5, 8–10).
The other ECP, called ella, contains an antiprogestin called ulipristal acetate. ella is only available with a prescription and is taken in either a single or split dose. ella is considered to be the most effective ECP and may be effective if taken until at least five days (120 hours) after unprotected sex (4, 7, 8, 11, 46).
When no other method is available, it is possible to use some types of daily-use oral hormonal birth control as emergency contraception (7). While not all brands can be used this way, many have specific instructions about use as emergency contraception (16). These pills are “combined pills” containing a mix of estrogen and progesterone. Multiple pills are usually taken in two doses — one dose within 4–5 days of unprotected sex, and another 12 hours later (16). This method has been shown to be less effective than other ECPs (7) and can cause stronger side effects than other pills, such as nausea and headaches (7, 12-17, 19), but may be more effective at preventing pregnancy than taking nothing.
ECPs should not be confused with the RU-486, the “abortion pill.” Unlike ECPs, RU-486 (Mifepristone) works by blocking hormones required for pregnancy, which can end a pregnancy after an embryo has implanted in the uterine wall (18–19, 20, 26, 27).
Intrauterine devices (IUDs) for emergency contraception
Copper IUDs are the most effective form of emergency contraception (7, 12, 21, 52). They are small devices, inserted into the uterus to prevent pregnancy. They’re a long-lasting contraceptive, and can stay in the body for up to ten years (7, 19, 22). This means you can get a copper IUD inserted as an emergency contraception, and then leave it in for continued contraceptive use.
Some hormonal IUDs work just as well as copper IUDs for emergency contraception (49, 52). These IUDs contain a specific amount of the progesterone hormone. They are called levonorgestrel 52-mg IUDs, also known as the Mirena or Lilletta (47, 48). Some people prefer the hormonal IUD over the copper IUD because it is also a long lasting contraceptive (up to 7 years) and can reduce menstrual pain and bleeding (47-49).
IUDs can be used as emergency contraception if they are inserted into the uterus up to five days after ovulation (7, 19, 21). Since the exact timing of ovulation is difficult to know, most sources recommend inserting the IUD up to five days after unprotected intercourse to ensure it will be effective and safe (22). IUDs cannot be inserted in the presence of certain active sexually transmitted infections (47, 48). They are inserted by healthcare providers in a clinic.
How do emergency contraceptive pills work?
Emergency contraceptive pills primarily work by blocking or delaying ovulation (4-12, 23–27, 36). They change the body’s hormones to prevent the release of an egg from the ovary. When ovulation doesn’t happen, sperm cannot come in contact with an egg. While an egg can only be fertilized by sperm for about 12–24 hours after ovulation happens, sperm can lead to a pregnancy for up to five days after it enters the body (1). It’s in this part of the fertile window before you ovulate that ECPs can be most effective, or perhaps effective at all (7, 9, 19-20, 31, 32, 36).
If you have unprotected intercourse several days before your ovulation and take an ECP, your chances of getting pregnant are much lower than if the same were to happen one day before ovulation (7, 9, 19, 27, 36). This is why ECPs should be taken as quickly as possible after unprotected intercourse — if an ECP is taken very close to ovulation, the hormones in the pill may not be able to prevent it, and you have a higher risk of pregnancy.
If your ovulation is days away, a levonorgestrel ECP and ella are both good choices (7-9, 19-20, 36). ella, the antiprogestin pill, has been shown to be more effective than other ECPs at preventing ovulation shortly before it happens (4, 7, 8, 11, 19, 31, 32). This means you may be safer choosing ella (or an IUD) if you think you are a day or two before your ovulation or if you are taking the pill 4–5 days after unprotected sex (19). If you don’t have access to ella or an IUD during that window of time, you can still take another type of ECP, but it may not be effective.
Research has studied if ECPs are effective in preventing pregnancy after ovulation by preventing an egg from being fertilized or implanted into the uterine wall (25, 33, 34). There is no conclusive evidence that ECPs are effective at preventing pregnancy once ovulation (or fertilization) occurs (9, 20, 27, 28, 33–35). In two recent studies of levonorgestrel ECPs, people who took the pill on or after the day of ovulation had the same number of pregnancies that would be expected in people who took nothing at all — about 1 in 3 (29, 30).
ECPs have been found to be more or less effective in people with different body types. Doubling or repeating doses of an ECP may improve their success in some people (52). You can discuss with your healthcare provider the best way for you to take an ECP. No matter what your body type or size, there are no safety concerns based on body size and people of all sizes who want to prevent pregnancy should have access to and use ECPs (7, 12, 19).
How do IUDs work as emergency birth control?
Unlike ECPs, IUDs are very effective at preventing pregnancy both before and after ovulation (at the end of the fertile window). They are also not affected by body type or size (7, 19, 49). A copper IUD works by preventing sperm from fertilizing an egg. Hormonal IUDs work by thickening cervical mucus, which can prevent sperm from traveling into the uterus. They can also make it more difficult for sperm to move and survive. This decreases their ability to fertilize an egg. IUDs also work by thinning the lining of the uterus, which can prevent an egg from embedding into the uterine wall (47, 49). Many times all of these steps contribute in preventing a pregnancy (47).
Copper IUDs are nearly 100% effective as emergency contraception, making them the most effective option (21). Recent research has shown that hormonal IUDs prevent pregnancies equally to Copper IUDs (49). IUDs do carry their own considerations for short and long-term use, and might not be right for everyone.
Note: If you think you are right around the time of your ovulation, and don’t have access to a Copper or Hormonal IUD, take an ECP.
Any method may be more effective than nothing, and it is easy to misjudge the timing of your ovulation (1, 3). If you suspect you may be pregnant, make an appointment with your healthcare provider — you should no longer take an ECP or have a copper IUD inserted after pregnancy (2, 47, 48).
What are the side effects of emergency contraception?
The side effects of ECPs can include headaches, abdominal pain, breast tenderness, dizziness, and fatigue, nausea, and vomiting (7, 9, 19). If you’re prone to nausea, it can be a good idea to take an ECP with an anti-nausea medication. If you vomit within two hours of taking an ECP, talk to a healthcare provider, as you may need another dose if you vomited up the medication.
Side effects often go away after about a day. Side effects tend to be stronger in combined-hormone ECPs (7, 12, 19). If you are worried about any side effects after taking an ECP, talk to your healthcare provider.
Some people wonder if there are any side effects to using ECPs frequently. ECPs are not recommended as a primary method of contraception (19). They are not as effective as correctly using other reliable birth control options, and repeated doses could cause higher levels of hormones with more negative side effects, like period irregularities (7, 19). Repeat use is unlikely to cause serious harm for most people and is safer than pregnancy (7, 12, 19, 31). ella is not recommended for use twice within the same cycle (36).
If you have a condition that increases risk with the use of combined or progesterone-only contraception, repeated use of an ECP may increase risk for you (7). You may be in a high risk group if you are over 35 and smoke more than 15 cigarettes a day or have clotting or heart conditions (42). Taking repeated doses will often cause changes in your period bleeding (7, 19).
Most people who take emergency contraception may get their next period sooner than expected, and this first period may be slightly longer than typical (19, 37–39). ECPs can also cause light spotting (non-menstrual bleeding) (37, 38).
People who don’t get their next period around the expected time should take a pregnancy test and contact their healthcare provider (12, 19). ECPs can delay ovulation making it easier to get pregnant later in your cycle. Using a barrier method like a condom or other birth control methods after using an ECP is important (19). You can start hormonal contraception immediately after taking a levonorgestrel ECP (like Plan B) but should wait five days after taking the antiprogestin ECP, ella (52).
Can I use emergency contraception if I’m pregnant or breastfeeding?
Taking an over-the-counter ECP if you are already pregnant has not been shown to cause harm to the fetus (40, 41), but don’t use an ECP if you are already pregnant.
Levonorgestrel ECPs are considered safe to take while breastfeeding/ chest feeding (9, 43). The effect of ella on human milk is not known (36, 43). The US Medical Eligibility Criteria reports that the benefits of emergency contraception and pregnancy prevention outweigh possible risks during nursing (42). Therefore ALL forms of ECPs should be made available to those breastfeeding/chest feeding (19). If you have questions about taking an ECP while nursing, talk to your healthcare provider.
Side effects of IUD insertion include pain and spotting (22, 47, 48 ). Some people may experience changes to their menstruation while the IUD is in place, and in some cases the IUD may be expelled through the vagina (22, 47, 48). Expulsion only happens 2-10% of the time. It’s more likely if you are younger than 20 years old, have heavy and painful periods, or have an IUD placed immediately after birth or a second trimester abortion (50, 51). Talk to your healthcare provider about these risks before having an IUD inserted.
Choosing an emergency contraception method
If you had unprotected sex and want to prevent pregnancy, there are four different options for emergency contraception. Now that you know your options, you can decide whether to choose a copper IUD, a hormonal IUD, an emergency contraceptive pill, or a type of daily-use oral hormonal birth control.
Remember that if you choose an oral birth control pill, you need to speak with a pharmacist or healthcare provider to make sure it is designed to be used as emergency contraception (16). Your healthcare provider should be able to give you specific instructions on how to use it. If you choose an IUD, this method may reduce your need for emergency contraception in the future. The most important thing to remember is that the sooner you take emergency contraception after unprotected sex, the more likely it is to work.
Using the Clue app to track your periods, ovulation date, and when you have sex can help you choose the right emergency contraception when you need it. Use custom tags to track contraceptive methods like emergency contraception.
An earlier version of this article was originally published on April 13, 2016.