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Emergency contraception

Emergency contraception
Literature review current through: Jan 2024.
This topic last updated: Nov 28, 2023.

INTRODUCTION — Emergency contraception (EC) refers to the contraceptive options that can decrease the risk of pregnancy after intercourse but before the establishment of a pregnancy. These methods can be used after intercourse when no contraception was employed (ie, unprotected intercourse [UPI]), a method was used imperfectly (ie, a condom slipped or broke, pills or injection were missed), or sex was forced without use of contraception. Clinicians should be able to educate patients about the multiple methods and ensure availability. EC can be offered to heterosexually active patients of all ages.

This topic will review the patient selection, counseling, and administration of EC. Related content on the general selection of contraception is presented elsewhere. (See "Contraception: Counseling and selection".)

In this topic, we will use the terms "woman/en" or "patient(s)" as they are used in the studies presented. However, we recognize that not all people who seek emergency contraception identify as women and we encourage the reader to consider the specific counseling needs of transgender and gender diverse individuals.

WHAT IS EMERGENCY CONTRACEPTION AND HOW DOES IT WORK?

Emergency contraception for prevention of pregnancy — EC refers to products that prevent pregnancy from occurring after an episode of unprotected intercourse (UPI). EC methods include oral medication and intrauterine devices (IUDs). UPI can be a result of contraception non-use or imperfect use or can result from forced sexual activity. EC does not interrupt an existing pregnancy; thus, it does not cause abortion.

EC must be initiated within a specific time frame from UPI in order to be effective; the time intervals vary by product (algorithm 1). It is not meant to be used as a regular contraceptive method but as a secondary method in the scenarios discussed previously. There are products dedicated to EC use and contraceptive methods, like the intrauterine devices and combined oral pills, that are used off-label for EC. All of these products are legal throughout the United States. (See 'What are the emergency contraception methods?' below.)

Mechanisms of action

Oral medication EC methods – Rigorous, meticulously executed studies have demonstrated that oral ulipristal acetate (UPA) and levonorgestrel (LNG) EC regimens prevent ovulation [1,2]. To be perfectly clear, oral EC is not an abortifacient, and this is very well understood.

LNG – LNG prevents ovulation if taken in the pre-ovulatory period by blocking the luteinizing hormone (LH) surge, thus inhibiting follicular development and egg release [3]. In December 2022, the U.S. Food and Drug Administration (FDA) changed the label for oral levonorgestrel 1.5 mg tablets (commercial name Plan B One-Step) and removed prior language suggesting that there may be a postovulatory (eg, a postfertilization or implantation) effect [2,4]. The Consumer Information Leaflet now clearly states that the drug works by inhibiting or delaying ovulation and through midcycle hormonal changes.

UPA – UPA delays ovulation in both the pre-ovulatory period and after the LH surge has started [1,5]. This extended period of activity may explain UPA's greater efficacy in preventing pregnancy compared with oral LNG.

Mifepristone – Low-dose mifepristone (available outside of the United States) also prevents ovulation; it binds to progesterone receptors to block progesterone's effects [6]. Mifepristone may also disrupt luteal phase events and endometrial development [7].

Neither LNG nor UPA prevents ovulation if taken on the day of the LH peak or later, nor do they prevent implantation [1,8,9]. None of these drugs interfere with implantation of a fertilized egg or an established pregnancy [10,11].

IUDs – Contrary to the clearly defined mechanisms of action for both oral EC methods, there is no clear description that fully explains the efficacy of the IUDs for EC. While data clearly support inhibition of fertilization as the primary mode of action for copper and levonorgestrel IUDs when they are used continuously, the mechanism for postcoital use is not clear [12]. However, there is no evidence to support a postimplantation effect, and as pregnancy is defined by implantation, these methods are not acting as abortifacients.

Copper 380 mm2 IUD – It is plausible that, just as with routine use where copper particles disrupt sperm and ovum function to prevent union as well as alter physiology in the uterus and fallopian tubes, postcoital copper 380 mm2 IUD placement may involve these same mechanisms. It is also possible that the exceptional efficacy of copper 380 mm2 IUDs for EC involves preventing implantation of a fertilized egg [13]. (See "Intrauterine contraception: Background and device types", section on 'Copper IUD'.)

LNG 52 mg IUD – In the case of LNG IUDs used for EC, it is unlikely the mechanisms supporting routine use, including development of a progestin-mediated thickening of the cervical mucus, would impact EC efficacy. However, laboratory data support the potential for LNG to directly interfere with sperm transport, sperm capacitation, the acrosome reaction, and oviduct transport [14-17]. Even without synthetic progestogens, clinical data demonstrate EC efficacy not only for copper 380 mm2 and levonorgestrel IUDs, but also for inert IUDs [18,19]. We lack a clear explanation of the mechanism of action for LNG IUD EC efficacy, and it is likely that a postfertilization effect may contribute to its efficacy in this setting.

WHAT ARE THE EMERGENCY CONTRACEPTION METHODS? — Options for EC include two types of intrauterine devices (IUDs), which are the most effective form of EC, and oral medications. EC methods discussed below and in the table (table 1) are presented in decreasing order of efficacy.

Intrauterine devices — When used for EC, both the copper 380 mm2 IUD and levonorgestrel (LNG) 52 mg IUD have first-cycle pregnancy rates of less than 1 percent, provide ongoing highly effective contraception, and are well tolerated [20,21]. In the United States, the copper 380 mm2 IUD is sold under the commercial name Paragard while the LNG 52 mg IUD is available under the commercial names Mirena and Liletta.

Copper 380 mm2 IUD

Efficacy – The copper 380 mm2 IUD (commercial name Paragard) is the most effective form of EC, with first-cycle pregnancy rates of 0.1 percent [20]. This is based on extensive use summarized in a systematic review including 7034 users from 42 studies. (See 'Emergency contraception efficacy' below.)

Insertion and use – While several guidelines advise the copper 380 mm2 IUD can be inserted within five days of UPI [22,23], the Society of Obstetricians and Gynaecologists of Canada recommends use within seven days of UPI [24]. If left in place, the device provides at least 10 years of reversible contraception [25]. (See 'Initiation and use' below.)

Comparison with oral EC drugs – The TCu380A reduces the risk of unintended pregnancies over the following year by one-half compared with those using oral LNG for EC [26] and continues to provide highly effective contraception for up to 12 years after insertion [27]. (See 'How effective is emergency contraception at preventing pregnancy?' below.)

Levonorgestrel 52 mg IUD – LNG 52 mg IUDs appear to provide effective EC and have the notable advantage that they can be left in place for long-term reversible contraception [21]. The information below applies only to LNG 52 mg IUDs (commercial names Mirena, Liletta); other LNG IUDs with less total LNG have not been studied for EC and should not be used for this purpose [28]. (See 'How effective is emergency contraception at preventing pregnancy?' below.)

Efficacy – EC data for the LNG 52 mg largely comes from a noninferiority trial comparing it with the copper 380 mm2 IUD that reported unintended pregnancy rates of 0.3 and 0.0 percent, respectively [21]. Pregnancy rates were not statistically different between the two devices, which led to the conclusion that the LNG 52 mg was noninferior to the copper 380 mm2 IUD for EC. At one year of follow-up, the unintended pregnancy and device discontinuation rates were similar for both groups, with one unintended pregnancy occurring for each IUD type [29]. Device superiority is not yet known.

Insertion and use – In the initial trial comparing LNG 52 mg with the copper 380 mm2 IUD, the device was inserted within five days from UPI [21]. It is not yet known if the LNG 52 mg IUDs (commercial names Mirena and Liletta) will provide EC beyond five days from UPI. The LNG 52 mg IUD devices are approved for contraception for eight years of use [30-33]. (See "Intrauterine contraception: Background and device types" and "Intrauterine contraception: Background and device types", section on 'Duration'.)

Comparison with other EC methodsLNG IUDs are often preferred by patients for long-term contraception because of the associated reduction in menstrual bleeding and cramping [34-36]. In addition, LNG 52 mg IUDs can be used by individuals of any body mass, treat heavy menstrual bleeding, and reduce endometriosis-related pelvic pain. (See "Intrauterine contraception: Background and device types", section on 'Levonorgestrel IUD'.)

Oral medication emergency contraception methods — Oral EC methods include products specifically marketed for EC and an alternate dosing regimen of oral contraceptive pills that contain both estrogen and a progestin (the Yuzpe method).

Ulipristal acetate (UPA) – UPA is a selective progestin receptor modulator (ie, antiprogestin) that at a dose of 30 mg can be used up to 120 hours (ie, five days) after UPI [37]. Commercial names include ella, ellaOne, and Fibristal. Progestin-containing contraceptives should not be used with UPA or for five days after UPA administration because of concerns that the progestin contraceptive will interfere with UPA action [37,38]. (See 'Initiation and use' below.)

Levonorgestrel (LNG) – Oral LNG 1.5 mg is licensed for use up to 72 hours after UPI [39], although it is used off-label beyond that time frame with established efficacy up to 120 hours (ie, five days) [40]. In regions where piroxicam is readily available and low cost, clinicians may prescribe oral LNG with a single dose of oral piroxicam 40 mg to increase efficacy, although this is not required as supporting data are limited [41]. Oral LNG as a method of EC is available over the counter in pharmacies without a prescription or age restriction. (See 'Emergency contraception efficacy' below and 'Initiation and use' below.)

MifepristoneMifepristone, in doses of 10 to 25 mg, is available in China, Russia, Vietnam, and other locations [6]. It is well studied and effective in this dose range, which is a small fraction of the 200 mg dose used for medication abortion and management of pregnancy loss [42,43]. A 2019 meta-analysis reported it is at least as effective as LNG and more effective than the Yuzpe method [44]. However, mifepristone 10 mg and 25 mg tablets are not available universally (200 mg and 300 mg doses are available in the United States).

Combined oral estrogen and LNG contraceptive pills (Yuzpe method) – The Yuzpe method can be an effective alternative when combined hormonal contraceptives using 100 mcg of ethinyl estradiol and 0.5 mg of LNG (or the equivalent) are available. Repeat dosing in 12 hours is required. There is no marketed version of this, but resourceful people who combine pills from an available pack that total 100 mcg of ethinyl estradiol will effectively reduce their risks of pregnancy. A listing of acceptable regimens based on commonly available combined oral contraceptive pills is available online. While the Yuzpe method is less effective and produces more side effects than the other oral EC methods, its wide availability and low cost can be good reasons to use it. This may be of greater importance in rural areas with greater challenges to access and privacy.

HOW EFFECTIVE IS EMERGENCY CONTRACEPTION AT PREVENTING PREGNANCY?

Baseline risk of pregnancy — Although pregnancy risk for EC users is very difficult to calculate, any person who presents for EC should be evaluated for it. The risk depends on many factors including whether the patient had sex in the fertile window, how many unprotected intercourse (UPI) exposures the patient had in the cycle, age, and imperfect use of a contraceptive method (condom slipped off or withdrawal) versus use of no method. Most EC users have not had UPI during the fertile window [45,46], and fewer than one-half of those presenting for EC have sperm present in the vagina [47]. However, EC users are still at high risk of pregnancy in the year after using oral EC, with annual pregnancy rates of 5 to 12 percent [26,48-51]. Thus, we discuss ongoing contraceptive needs with patients who present for EC. (See 'Initiating ongoing contraception' below.)

Emergency contraception efficacy — Intrauterine devices (IUDs) are the most effective EC method. The risk of pregnancy following placement of a copper 380 mm2 IUD is 0.1 percent (ie, the copper 380 mm2 IUD reduces the risk of pregnancy after UPI by more than 99 percent) [20]. Early data suggest the 52 mg levonorgestrel (LNG 52 mg) IUD has an unintended pregnancy rate of 0.3 percent [21]. This efficacy is not statistically less than the copper 380 mm2 IUD and is five- to eightfold lower (ie, more effective) compared with oral medications.

Relative to the IUDs, efficacy drops considerably with use of oral EC methods. Data from trials comparing ulipristal acetate (UPA) and oral LNG report respective pregnancy rates of 1.8 percent for UPA versus 2.6 percent for LNG [5,52-55]. An earlier trial by the World Health Organization (WHO) that compared oral LNG with mifepristone 10 mg reported a pregnancy risk of 1.5 percent for both [52], though mifepristone efficacy likely varies with dose [6]. Importantly, the risk of pregnancy increases with increasing body mass index (BMI) for both UPA and LNG [56]. Other risk factors for pregnancy despite EC use include UPI in the fertile window and continued UPI after EC use [56]. (See 'Initiation and use' below and 'Impact of body weight' below.)

Device-specific efficacy data – Overall, the level of confidence in copper T380A IUD EC data, based on the large number of trials and participants reporting pregnancy rates ≤0.1 percent, is far greater than one efficacy study of the LNG 52 mg IUD EC. An ongoing prospective observational trial is attempting to reproduce the initial LNG 52 mg IUD EC results. This study will enroll 853 LNG 52 mg IUD EC users at eight diverse sites in the United States [28].

Copper 380 mm2 IUD – Data supporting use of the copper 380 mm2 IUD come from a systematic review of over 7000 IUD placements, including eight different IUD types (including a small proportion of inert IUDs) inserted over varying time frames in six countries between 1979 and 2011, that reported a pregnancy rate of 0.09 percent [20]. The largest study included used only the copper T380A IUD and reported zero pregnancies among 1963 users [57]. Review of included studies that limited the time of insertion to 120 hours (ie, five days) reported failure rates of 0 to 0.1 percent. Unlike oral methods of EC, there is no evidence to suggest that copper 380 mm2 IUD efficacy for EC varies by menstrual cycle timing, time since UPI, the number of episodes of UPI in the cycle of EC use, or the patient's body weight. A growing pool of data supports IUD EC efficacy when inserted more than five days after UPI [45,58]. Another benefit of the copper 380 mm2 IUD is provision of ongoing contraception in addition to EC; it is highly effective at preventing pregnancy for up to 12 years [27].

LNG 52 mg IUD – Research on the LNG 52 mg IUD for EC is newer and less robust. In the case of the copper IUD for EC, our confidence in the low pregnancy rate (0.1 percent) comes from a multitude of studies conducted in a variety of countries with consistent agreement in results (excluding one study from Egypt). In comparison, data for the LNG 52 mg IUD for EC come from a single noninferiority trial in which 317 participants received the LNG IUD and reported one-month pregnancy outcomes [21]. That study randomly assigned 711 females who presented within five days of UPI and desired EC to either an LNG 52 mg or copper 380 mm2 IUD. Participants reported pregnancy rates of 0.3 percent (1 of 317) and 0.0 percent (0 of 321), respectively [21]. All trial participants had a negative urine pregnancy test at the time of IUD placement and were masked to the IUD type they received for the first month of use. The pre-study noninferiority margin of 2.5 percentage points was met as the pregnancy incidence difference between the two methods was 0.3 percent (95% CI -0.9 to 1.8 percent). This study concluded the LNG 52 mg IUD is not less effective than (or noninferior to) the copper 380 mm2 IUD for EC. These results do not permit us to say that one IUD is superior or inferior to the other for EC.

Adverse events causing the participants to seek medical care within the first month after IUD placement were low in both groups (5.2 percent of LNG 52 mg IUD users and 4.9 percent of copper 380 mm2 IUD users). The most common adverse events were bleeding, cramping, and pain. Study strengths were inclusion of patients with both a range of BMIs and more than one episode of UPI.

Ulipristal acetate – Large prospective studies of UPA, the most effective oral EC method, report single-cycle pregnancy rates of 1.2 to 1.8 percent [5,44,54]. In clinical practice, the author informs UPA EC users that if 100 people use the medicine, one to two people will have a positive pregnancy test in the next two to three weeks. In these studies, UPA efficacy did not drop over the 120-hour (ie, five-day) time frame after UPI. A meta-analysis of two trials comparing UPA with LNG demonstrated that UPA was more likely to prevent pregnancy in the first 120 hours after UPI (odds ratio 0.55, 95% CI 0.32-0.93) [54]. In pharmacokinetic evaluations, UPA more effectively prevented ovulation at all times relative to LNG, and UPA continued to prevent ovulation through the onset of the luteinizing hormone (LH) surge, while LNG only prevented ovulation prior to the surge [1].

Oral LNG – For LNG, single-cycle pregnancy rates with a single episode of UPI range from 1.7 to 2.6 for all enrolled in large trials [41,44,54]. The highest risk of pregnancy for oral LNG EC users, 7.3 percent, is in patients reporting repeated acts of intercourse later in the cycle [56].

-Duration of efficacy – Although the LNG package insert states that efficacy is maintained up to 72 hours from UPI, subsequent studies have demonstrated no reduction in efficacy for up to 120 hours (ie, five days) from UPI [40,59,60]. The 72-hour window was based on data from earlier trials [52,61]. While the author counsels patients that LNG can be used up to five days from UPI, patients are also advised to take LNG as soon as possible to increase the likelihood that the medication is used prior to the LH surge. After the LH surge, LNG is no longer effective. (See 'Mechanisms of action' above.)

-Combined treatment with piroxicam – Taking oral LNG with a single dose of piroxicam appears to increase efficacy (ie, lower the unintended pregnancy rate). A trial including 860 patients with a single act of UPI reported that patients receiving combined treatment with LNG and piroxicam 40 mg orally had lower pregnancy rates compared with those receiving LNG/placebo (0.2 versus 1.7 percent, OR 0.20, 95% CI 0.02-0.91) [41]. Although definitive conclusions cannot be made from one trial that included a patient population with only a single UPI exposure, dual treatment is reasonable if piroxicam is readily available (ie, over the counter) and there are no contraindications to its use [41]. Of note, this study was conducted in Hong Kong with participants with a mean BMI of 21 kg/m2 (only 10 percent of whom had a weight >70 kg or BMI >26 kg/m2). This creates some limitations in applying the data to heavier populations.

Mifepristone – The aggregate of data supporting mifepristone use shows that it is more effective than the Yuzpe method and likely more effective than LNG at the low-dose range (<25 mg) and the mid-dose range (25 to 50 mg) [44].

Data limitations – One important consideration when using published data to evaluate pregnancy risk among EC users in the clinical setting is that nearly all of these studies limit inclusion criteria to females having only a single episode of UPI in the cycle with EC treatment [44]. However, among routine EC users, multiple episodes of UPI occur in the cycle that EC is used. In a study of 176 IUD EC users who were known to not be pregnant, 43 percent reported multiple episodes of UPI in the 14 days prior to presenting for EC [62]. Those with multiple episodes of UPI in the cycle are the EC users with the highest risk of pregnancy. The IUDs provide additional benefit for this group as they are the most effective EC method and provide ongoing pregnancy prevention for this group that is likely at continued high risk.

WHICH METHOD SHOULD I PICK?

Comparison of all methods — Selection of an EC agent is driven by patient preference but must also consider method characteristics, availability, and cost (table 1). Patient-important variables include desire to initiate the most effective EC, desire for long-term contraception, and desire to initiate hormonal non-IUD contraception (algorithm 1). While intrauterine devices (IUDs) are the most effective EC method, they require a visit with a medical provider, take the most time to obtain, and are the most expensive for those without insurance coverage. In addition, some people simply do not want an IUD because they have previously tried one without satisfaction, do not desire a foreign material in their body, or have a range of other reasons. Ulipristal acetate (UPA) is the most effective oral method but requires a prescription and is not stocked by all pharmacies. Finally, oral levonorgestrel (LNG), the least effective oral agent, should be available in any pharmacy without a prescription and should be the easiest to obtain. However, this generally requires an out-of-pocket expense in excess of USD $40 (can be as low as USD $10 with internet-based purchasing), and it is not provided in all pharmacies or may be placed behind the pharmacy counter in others. The choice of EC must ultimately balance all of these factors.

Advantages of intrauterine devices for emergency contraception — IUDs have significant advantages over oral EC methods, and there are very few contraindications to IUD EC use. Main advantages of IUDs for EC include:

Both are highly effective and more effective than oral EC methods. As the efficacy data for the LNG 52 mg (0.3 percent) are limited compared with the copper 380 mm2 IUD (0.1 percent), the body of evidence does not permit us to say that one IUD is superior or inferior to the other for EC. However, the data supporting copper IUD EC efficacy are certainly more robust than that for the LNG 52 mg IUD.

Continue to provide ongoing, highly effective contraception for years after EC use. One-year continuation rates of approximately 60 percent have been reported for both devices [29].

Can be used in individuals of any weight or body mass index (BMI) without a decrease in EC efficacy.

Work well for individuals regardless of timing of the menstrual cycle relative to unprotected intercourse (UPI).

Data suggest they are effective for UPI occurring 6 to 14 days prior to IUD insertion [63].

Intrauterine device selection — IUD selection for EC is guided by user preferences for the unique characteristics of each device.

Favoring the copper 380 mm2 IUD – The copper 380 mm2 IUD provides the most effective EC method, can remain in place up to 12 years [27,64], maintains regular menstrual cycles, and does not contain hormones. (See "Intrauterine contraception: Background and device types", section on 'Copper IUD'.)

Favoring the LNG 52 mg IUD – The LNG 52 mg IUD results in less or no menstrual bleeding and cramping, can remain in place up to eight years [65], and has the potential for amenorrhea. An ongoing study will provide more precise efficacy data on the LNG 52 mg IUD for EC [28]. (See "Intrauterine contraception: Background and device types", section on 'Levonorgestrel IUD'.)

Past studies have reported only a minority of EC users (approximately one in eight) would consider an IUD [66,67]. It is not known how the option of the LNG 52 mg will impact the frequency of IUD use for EC.

COUNSELING POINTS

Candidates — Any reproductive female, of any age, who has had unprotected or under-protected vaginal intercourse and wishes to reduce the risk of pregnancy is a potential EC candidate [68,69]. The author and other experts advise that every individual who thinks they may be at risk of unwanted pregnancy and considers taking EC should take it. This advice is based on study data indicating that asking women to identify their fertile window based on menstrual cycle dates is highly inaccurate when compared with laboratory testing [46].

EC is safe for the majority of patients. Pregnancy is the only absolute contraindication to EC use because EC will not work if a pregnancy is established [37,39]. Individuals with a contraindication to the copper 380 mm2 IUD (eg, current pelvic inflammatory disease or a uterine anomaly) or oral medications (ie, drug allergy) should receive alternate methods. The US Medical Eligibility Criteria for Contraceptive Use suggests no restrictions for UPA or LNG EC for breastfeeding individuals [22]. (See 'Special populations' below.)

Impact of body weight

Tcu380A IUD and LNG 52 mg IUD – Body weight does not impact the efficacy of either IUD, which in part contributes to its overall high efficacy [20,21].

Oral medications – EC efficacy for LNG appears to decrease with increasing body mass index (BMI), both for overweight (BMI 25 to 29.9 kg/m2) and obese (BMI ≥30 kg/m2) individuals.

Oral levonorgestrel – Studies suggest that LNG EC may not reduce the risk of pregnancy for individuals with obesity [56,70]. However, LNG data from pooled World Health Organization (WHO) studies reported a less dramatic effect [71]. This information has public health significance, as the prevalence of obesity among United States females ages 20 to 34 exceeds one-third of the population (34.8 percent) [72].

-Pharmacokinetic data – Pharmacokinetic data provide insight into the clinical data. A study that compared serum metrics following the 1.5 mg oral dose of LNG in 10 normal-weight (mean BMI 22 kg/m2), 11 obese (mean BMI 34.4 kg/m2), and 5 extremely obese (mean BMI 46.6 kg/m2) women reported lower mean total serum maximum concentrations and areas under the curve for obese and extremely obese women [73]. A study comparing serum LNG levels in five women with normal BMI (18 to 24.9 kg/m2) versus five obese women (BMI ≥30 kg/m2) reported that, after an oral dose of 1.5 mg LNG, obese women had LNG serum levels one-half those of the controls [74]. When the oral LNG dose was doubled to 3 mg, the serum level in obese women reached the level of the 1.5 mg control women. A different study that compared serum levels of LNG and UPA in 16 normal and obese women, in a crossover design, reported that obese participants had LNG levels one-half of the normal BMI participants [75].

-Role of doubled dose – One proposed solution has been to use double the usual LNG dose (3 mg instead of 1.5 mg) for individuals with obesity. One study reported similar serum LNG levels for five self-reported women with obesity compared with five control women when those with obesity received double the LNG dose (3.0 mg versus 1.5 mg) [74]. However, in a subsequent study that assessed timing of ovulation in 70 self-reported women with obesity who received LNG 1.5 mg or 3 mg, ovulation (identified by follicle rupture) occurred for similar numbers of participants in the two groups (LNG 1.5 mg: 18 in 35 [51 percent] and LNG 3.0 mg: 24 in 35 [69 percent], p = 0.14) [76]. In addition, for those with evidence of follicle rupture, timing of ovulation was similar for both groups (ie, there was no delay). Thus, we do not use a doubled dose of LNG for EC in individuals with obesity as it does not appear to suppress or delay ovulation adequately to function as EC for these patients.

Ulipristal acetate – The impact of overweight and obesity on UPA levels is unclear as evidence is limited. In a cross-over study comparing serum levels of LNG and UPA in 32 self-reported women of normal weight or with obesity, serum UPA levels did not differ between the groups [75].

Impact of malabsorptive bariatric surgery – For those who have had malabsorptive bariatric procedures, LNG absorption is likely compromised, and LNG levels are low [77]. Data for UPA are not available for these patients. Thus, the most effective, and possibly the only effective, EC method in this group are the IUDs. (See "Bariatric procedures for the management of severe obesity: Descriptions", section on 'Procedures endorsed by the ASMBS'.)

Side effects — Overall, all EC methods are safe and well tolerated; the side effect profiles vary by the method.

For the copper 380 mm2 and LNG 52 mg IUD, side effects can include abdominal or pelvic pain resulting from insertion, bleeding, uterine perforation, and, rarely, infection. These issues, which are generally of low risk and treatable, are discussed in detail in a related topic. (See "Intrauterine contraception: Management of side effects and complications".)

Both UPA and oral LNG are exceptionally safe and avoid the rare major complications of combined hormonal contraception, specifically estrogen-related thrombogenic events. In the initial clinical trials, common side effects of UPA included headache (18 percent), abdominal pain (12 percent), nausea (12 percent), dysmenorrhea (9 percent), fatigue (6 percent), and dizziness (5 percent) [37]. For LNG, common side effects were similar and included menstrual changes, nausea, lower abdominal pain, fatigue, headache, dizziness, breast pain, and vomiting [39].

For the Yuzpe method of using combined estrogen and LNG birth control pills, the main side effects are nausea and vomiting, which occur more often with this method compared with UPA, LNG, or mifepristone [44,68]. For this reason, patients using this method are often prescribed anti-nausea medication as well. (See 'Initiation and use' below.)

Sexually transmitted infection risk — Use of EC does not reduce the risk of sexually transmitted infections (STIs). We discuss regular condom use with all patients who are at risk of acquiring an STI. Information on STI screening is presented separately. (See "Screening for sexually transmitted infections".)

Patient satisfaction — Data on patient satisfaction with various EC methods are sparse. A prospective study of 79 women choosing either the copper 380 mm2 IUD or UPA for EC reported that, at six-month follow-up, 86 percent of copper 380 mm2 IUD users said they would recommend the copper 380 mm2 IUD for EC and 64 percent had already recommended the method [78].

ADMINISTRATION

Common clinical scenarios — Most EC users use oral EC and obtain it without an office visit with a medical provider. However, there are several clinical encounters where it is appropriate to discuss EC alternatives and characteristics. Clinicians should be aware that patients who could benefit from EC do not always know that it is available or how to access it.

Identified unprotected intercourse (UPI) – In some cases, patients inform the clinician that they had UPI in the last five days. However, from the author's clinical experience in a variety of primary care, female reproductive health, and family planning settings, few clients schedule an appointment specifically to request EC. More commonly, recent UPI is disclosed as part of the sexual history for another related issue. Thus, clinicians can consider every visit with a reproductive-age female an opportunity to ask about EC need or provide information about potential future use, if needed, along with a prescription for ulipristal acetate (UPA).

New contraceptive start – A patient who presents to start or change contraceptive methods may report recent UPI upon questioning, and thus the opportunity for EC use becomes apparent. The Centers for Disease Control and Prevention (CDC) provides questions to reasonably exclude pregnancy (table 2). If the patient answers "yes" to any of these six questions at the time of the visit, then contraception can be started directly, without using EC, and no urine pregnancy test is needed. However, people commonly present for care when they are not in the first seven days of their menstrual cycle and have had intercourse since the start of their last normal menses, which eliminates two of the CDC questions. In these situations, the choice of EC depends in part on the desired contraceptive and the balance of maximum EC efficacy versus immediate contraceptive start. (See 'Which method should I pick?' above and 'Initiating ongoing contraception' below.)

Sexual assault – In cases where individuals present for care related to recent sexual assault or it is revealed during a clinical encounter, EC should be offered [79]. The Royal College of Obstetricians and Gynaecologists Faculty of Sexual and Reproductive Healthcare recommends offering the copper 380 mm2 intrauterine device (IUD), the most effective method of EC, to everyone at risk of pregnancy after a sexual assault [80]. Ideally, this should immediately follow forensic examination for specimen collection. Emergency departments in other regions, including the United States, are often not equipped for IUD insertion as part of sexual assault evaluation. (See "Evaluation and management of adult and adolescent sexual assault victims in the emergency department".)

If the copper 380 mm2 IUD is not available or desired by the patient, the patient should be offered oral EC. Many emergency departments now have an established protocol for providing EC in this setting, though by law only 18 states and the District of Columbia require offering EC to sexual assault victims [81].

Initiation and use — The use of oral EC does not require a routine physical examination, pregnancy test, or laboratory tests [68,80]. Unless patients have missed a menstrual cycle or think they may be pregnant (table 2), use of EC should not be delayed or withheld to check for pregnancy [82]. By contrast, it is clinically appropriate to conduct a urine pregnancy test prior to IUD EC placement as this has been the practice for studies of IUDs for EC.

Copper 380 mm2 and levonorgestrel (LNG) 52 mg IUDs – IUDs should only be inserted by clinicians who have received appropriate training. Detailed instructions for IUD insertion are reviewed separately. (See "Intrauterine contraception: Insertion and removal".)

Standard insertion timing – The copper 380 mm2 and LNG 52 mg IUDs can be inserted up to five days from UPI and likely longer [23,24,63,82].

Extended timing of insertion – There is a growing body of data that demonstrates low pregnancy rates with UPI occurring beyond five days prior to IUD placement.

-In a secondary analysis of a trial comparing copper 380 mm2 and LNG 52 mg IUDs in 655 participants presenting for EC, similar pregnancy rates were reported by individuals with all UPI five or fewer days prior to IUD insertion compared with those also reporting UPI 6 to 14 days prior to IUD insertion (0.2 percent, 95% CI -0.2 to 0.5) [63].

-For the Tcu380A IUD, an aggregated data set reported no pregnancies in 134 people receiving an IUD and having UPI 6 to 14 days prior to IUD placement (0 percent, 97.5% CI 0-2.7 percent) [83].

-Two other studies reported zero pregnancies among an additional 116 participants reporting UPI more than five days prior to copper 380 mm2 IUD placement. Collectively, the three Tcu380A studies would provide a pregnancy risk of 0 percent (97.5% CI 0-1.5 percent) [45,58,83]. This same dataset reported one pregnancy among 187 LNG 52 mg IUD users with UPI 6 to 14 days prior to IUD placement (0.5 percent, 95% CI 0.01-2.9 percent) [84].

Even prior to the publication of most of these data, the Society of Obstetricians and Gynaecologists of Canada advised IUD use within seven days of UPI, and the World Health Organization says the copper 380 mm2 IUD can be inserted beyond five days from UPI if the timing of ovulation can be estimated and the insertion does not occur more than five days after ovulation [23,24].

Our approach – Based on the information above and other studies, we take the following approach for anyone who wants an IUD, reports UPI >5 days prior, and has a negative urine pregnancy test:

-Counsel about risk of pregnancy – We counsel that the risk of pregnancy for this menstrual cycle with IUD placement is very low (likely <1 percent). This estimate is extrapolated from a much smaller data set compared with data supporting other EC recommendations because identifying people >5 days from UPI is more challenging and these individuals were excluded from most EC studies. It is difficult to obtain information on pregnancy risk with UPI >5 days prior without IUD placement to compare.

-IUD insertion >5 days after UPI – For individuals who desire an IUD insertion (either copper 380 mm2 or LNG 52 mg IUD) for EC and report UPI >5 days prior, we counsel patients that they must have a negative pregnancy test, accept the potential risk of conception with an IUD in place, understand the follow-up care plan, and be able to return should they have a positive pregnancy test two to four weeks after IUD insertion. Our willingness to insert an IUD for EC beyond the usual time frame is extrapolated from studies reporting that individuals who are required to have a delayed contraceptive start are more likely to experience unintended pregnancy compared with individuals who receive immediate contraception [85-89].

Oral EC – Oral EC should be taken as soon as possible after UPI. The maximum allowable interval varies by medication.

UPA – UPA is given as a single 30 mg oral dose to be taken as soon as possible after UPI, up to a five-day (120-hour) interval [37]. In our practice, we include refills on the prescription for future use. If UPI occurred four or five days prior to the visit, we inform patients desiring oral EC of the superior efficacy of UPA over LNG in this setting. The patient is advised to use a barrier method (condoms) or abstain from vaginal intercourse for at least five days after taking UPA. Hormonal contraception should not be started sooner than five days after taking UPA because exposure to progestins from seven days prior to five days after UPA use can decrease UPA's ability to block ovulation [90]. The section on initiating ongoing contraception addresses this in greater detail. (See 'Initiating ongoing contraception' below.)

LNG – LNG is available as a single oral 1.5 mg dose, to be taken as soon as possible after UPI, up to three days (72 hours) [39]. There may be some efficacy up to five days (120 hours) [39,40,54]. LNG efficacy is likely higher the earlier the drug is taken within the 72-hour window. The longer someone who has not yet ovulated waits to take LNG EC, the greater the chance they may progress to the point of the luteinizing hormone (LH) surge and thus lessen the efficacy of LNG EC. In the United States, single-dose LNG (available under multiple commercial names, including Plan B One-Step) is available over the counter without age restrictions [68]. Although LNG has also been available in two doses of 0.75 mg each, the one-dose approach is favored because of simpler dosing and efficacy that is at least as good [52,91]. Combined treatment with piroxicam 40 mg orally, taken at the same time, may increase LNG efficacy [41]. (See 'Emergency contraception efficacy' above.)

Mifepristone – Outside of the United States, mifepristone is available for EC in oral doses of 10 to 25 mg. Dose selection depends on regional availability.

Yuzpe method of combined oral contraceptive pills – Combined oral contraceptive pills that contain ethinyl estradiol and either norgestrel or LNG can be used as EC but must be taken in a dosing pattern that is very different from use as an oral contraceptive. Data are lacking on use of oral contraceptive pills with other progestins for EC. To provide EC, the initial dose must contain the equivalent of 100 to 120 mcg of ethinyl estradiol and 0.5 to 0.6 mg of LNG (or the equivalent) [6]. The same dose is then repeated 12 hours after the first dose. A list of contraceptive pill brands and how to use them for EC is presented online. Some clinicians also advise taking meclizine 50 mg orally with the first dose to reduce nausea. Use of the Yuzpe method should be reserved for situations where people can obtain combined oral contraceptive pills but cannot obtain a dedicated EC product within two to three days.

What if oral medication is vomited? — Data to guide repeat dosing of oral EC in the setting of vomiting are lacking, in part because vomiting is rare with LNG and UPA formulations [6]. At least one guideline advises repeat dosing of oral EC if the patient vomits the medication within three hours of ingestion [92]. When receiving clinical calls from patients on this topic, the author anticipates that if the medication level was high enough to induce vomiting, then it was also likely high enough to interrupt ovulation. However, for patients with a secondary reason for vomiting (eg, viral illness) or a short time interval from initial ingestion to vomiting (<1 hour), the author asks the patient to take a repeat dose.

What happens to the menstrual cycle? — For patients using oral EC, the menstrual period typically restarts within one week of the anticipated date [60]. Resumption of menses within a week of the anticipated start is more common following UPA than LNG; menstrual delay is most common following mifepristone and appears to be dose related [44]. Irregular bleeding or spotting can also occur and continue up to a month after treatment [68]. Any irregular bleeding should resolve without treatment. We reevaluate patients with persistent bleeding to exclude pregnancy.

Use of the copper 380 mm2 IUD as EC does not significantly impact the timing of the menstrual cycle. Data evaluating the return of the menstrual cycle after LNG 52 mg IUD placement for EC are not yet available, though it is reasonable to expect an increase in bleeding and spotting in the first three months of LNG IUD use as is typical when placed for ongoing contraception. (See "Intrauterine contraception: Background and device types", section on 'Impact of device type on bleeding pattern'.)

Can oral emergency contraception be used again in the same cycle? — Both UPA and LNG can be used multiple times in the same menstrual cycle, although initiation of a proven contraceptive method is preferred to this approach [68]. Oral LNG 1.5 mg has been tested as an as-needed contraceptive for women with <6 episodes of intercourse per month [93]. Among 321 enrollees, there were 142 women-years of use. The typical-use pregnancy rate was 7.1 per 100 women-years. More than 80 percent of users had frequent bleeding episodes, defined as more than five per 90-day period, and despite this, 90 percent of participants said they would use the method again.

Should I prescribe emergency contraception in advance? — Providing a prescription for UPA in advance for anyone interested is reasonable, along with information about the need to delay starting hormonal contraception for five days after UPA use. In addition, information about over-the-counter availability of oral LNG for EC is appropriate. The International Consortium for Emergency Contraception advises providing an advanced prescription or supply of EC because no clinician screening or assessment is required and this enables treatment to be started as soon as possible [94]. One approach to this is to offer a prescription for UPA and information about oral LNG EC available over the counter for any person starting a new contraceptive method. For those who decline advance provision, practices can inform clients that they will prescribe by telephone without an office visit in the future, if needed. While advance provision usually means providing education and treatment options for females, it is entirely reasonable to provide the same for males who are heterosexually active [95].

While advance provision of EC is both logical and reasonable, a meta-analysis of 11 trials did not show a decrease in overall pregnancy rates over 12 months with this approach (odds ratio 0.98, 95% CI 0.76-1.25) [96]. Advance provision did result in increased EC use (both single and multiple use) as well as use sooner after UPI. Rates of sexually transmitted infections (STIs), frequency of UPI, and changes in contraception did not increase with advance provision of EC.

INITIATING ONGOING CONTRACEPTION

Assess need for continued contraception — EC use provides an opportunity to inquire about ongoing contraceptive needs (algorithm 1), but the author's experience suggests that there is a significant proportion of EC users who only want an EC method delivered with the fewest obstacles and are not interested in counseling on ongoing contraceptive methods. EC users should be offered ongoing contraception and may need a restart of a method they were previously on or a method they used intermittently. Sometimes, these patterns of inconsistent use are driven by challenges accessing a method or a desire to switch methods. These factors can be important drivers in selecting ongoing contraception. Individuals who do not wish to discuss ongoing contraceptive needs at the time of an EC visit may benefit from scheduling a future appointment to further discuss these issues.

When to start contraception after emergency contraception — The future risk of pregnancy in those presenting for EC highlights the need for initiating ongoing contraception for those with interest. The timing of contraceptive start and need for backup contraception or abstinence vary with the EC method (table 3 and algorithm 1):

Tcu380A copper 380 mm2 or levonorgestrel (LNG) 52 mg intrauterine devices (IUDs) – Both the copper 380 mm2 and LNG 52 mg IUDs provide EC and ongoing contraception, with no need for an interval of backup contraception or abstinence. This is the simplest approach and provides the highest efficacy for both EC and contraception, particularly given that backup contraception is unlikely to be used. One study of 518 individuals given either the Tcu308A or LNG 52 IUDs reported that 64 percent resumed penile-vaginal intercourse within seven days of IUD insertion but only 16 percent used a form of back-up contraception [97]. No pregnancies occurred in either group. (See 'Emergency contraception efficacy' above.)

Ulipristal acetate (UPA) – Barrier and pericoital contraceptives (ie, nonhormonal contraception) can be used immediately after UPA treatment; no period of abstinence is required [82]. Women who desire progestin-containing contraceptives are advised to delay start of the contraceptive for at least five days from UPA ingestion [82]. There is concern that earlier start of a progestin-containing contraceptive could interfere with UPA function and reduce UPA's ability to block ovulation [37,38,90].

However, clinicians should be aware that the five-day delay is a conservative approach. Five days is also the duration of sperm viability after intercourse. As a result, an alternative approach is to begin hormonal contraception five days after the most recent episode of unprotected intercourse (UPI) [98]. A thoughtful commentary addressing this issue advised waiting five days from UPI (not UPA ingestion) and also cautioned about applying results from a study with desogestrel to other progestins and combined hormonal contraceptives [98]. In addition, the study author acknowledged that clinicians should counsel EC users to weigh risks of pregnancy from recent UPI against future pregnancy risk based on contraceptive access and ability to return for future care. An approach to dealing with these issues is presented in the reference [99].

Oral LNG – Barrier and pericoital contraceptives (ie, nonhormonal contraceptives) can be used immediately after LNG treatment; no period of abstinence is required [82]. For anyone who selects LNG EC and desires a contraceptive method with a progestin, the advice is the same: provide oral LNG for EC, initiate the contraceptive method at the same time as the LNG EC, and either abstain from sex or use a backup method of contraception for one week [82]. Backup contraception can include condoms (female or male) or pericoital contraception (diaphragm, contraceptive sponge, or cervical cap).

While this approach is the next simplest after copper 380 mm2 IUD insertion, it is not the most effective EC option. However, this approach may be preferred when the risk of pregnancy from the recent episode of UPI is low and the user is more concerned about preventing future pregnancy. An advantage is that the desired contraceptive can be started immediately with a backup method for one week as indicated.

Mifepristone – Like LNG, mifepristone EC users can initiate any form of contraception with or immediately after EC. The patient should also use a backup barrier contraceptive or abstinence for the first week following mifepristone EC use.

Yuzpe method of combined estrogen-progestin oral contraceptives – Individuals who use the Yuzpe method can start any method of contraception after taking the second dose of EC pills [82]. Those who elect to start hormonal contraception are advised to abstain from vaginal intercourse or to use a backup contraceptive for seven additional days. Backup contraception can include condoms (female or male), diaphragm, contraceptive sponge, or cervical cap.

Case scenarios by contraceptive type — For females who present for EC and have a preferred contraceptive method to restart or initiate, the selection of EC is influenced by the planned contraceptive. The choice of EC agent must balance the potential impact of EC on the desired contraceptive method start time and the impact of the contraceptive itself on EC efficacy.

Individuals who desire an IUD for contraception (copper 380 mm2 or LNG) – Patients who present for EC and wish to use an IUD for contraception can choose from the copper 380 mm2 or LNG 52 mg IUD. However, if patients desire the absolute greatest level of certainty against pregnancy, greater consideration should be given to the copper IUD. (See 'Initiation and use' above.)

Individuals who desire a progestin-containing contraceptive – Progestin-containing contraceptives include the LNG IUDS; etonogestrel implant; depot medroxyprogesterone acetate (DMPA) injection; combined estrogen-progestin pills, patches, and rings; and progestin-only pills. For individuals who desire any of these methods other than the LNG IUD, the patient and clinician must balance oral EC efficacy with timing of initiation and efficacy of the desired progestin-containing contraceptive. While UPA is associated with lower pregnancy rates, it also requires a delayed start of progestin-containing contraceptives (table 3 and algorithm 1), which may necessitate another visit (for the etonogestrel implant or DMPA injection) and may increase the patient's risk of future pregnancy if no contraception is started. However, as UPA is the most effective oral EC, it may be ideal for those at high risk of pregnancy based on recent UPI who prioritize reducing immediate pregnancy risk over ongoing contraception start. Oral LNG EC has a lower efficacy but can be given simultaneously with any progestin-containing contraceptive (plus seven days of abstinence or backup contraception). This approach may be preferred for individuals at lower risk of pregnancy relative to UPI and who prioritize immediate contraceptive start and/or avoiding repeat visits (and additional cost).

For example, a person on cycle day 12 of a 28-day cycle presents to have an etonogestrel implant placed and reports having intercourse two days previously, during which the partner's condom slipped. If the patient desires oral EC and insertion of the etonogestrel implant, oral EC selection (LNG versus UPA) requires balancing EC efficacy with the patient's desire for immediate versus delayed implant insertion. If immediate implant insertion is prioritized, it is appropriate to provide oral LNG for EC and insert the device as long as the user is willing to accept the small increased risk of pregnancy with LNG compared with UPA and is willing to use abstinence or a barrier method for one week. This approach carries a minimal risk for individuals with a normal body mass index (BMI) who are within 72 hours of UPI. The counseling to use oral LNG for EC would also be appropriate for someone with this history who desires initiation of a combined hormonal method (pills, patch, or ring) or intramuscular DMPA. While UPA is a more effective oral EC method, its use is challenging in this setting because UPA may not be able to block ovulation in the setting of the additional progestin (ie, if the implant is placed at the same time) [90]. If UPA is used in an effort to provide a more effective method of oral EC, then the progestin-containing contraceptive method, in this case the etonogestrel implant, should be initiated more than five days after UPI, which will require an additional visit. In addition, abstinence or a barrier method (condoms) should be used until the new method has been in use for at least one week.

There has been hesitancy among clinicians to start long-acting reversible contraceptive methods other than the IUDs following oral LNG, but published data can favorably inform this practice with reported pregnancy risks of approximately 1 percent when oral LNG was provided to women initiating the etonogestrel implant, LNG IUD, or DMPA injection [100-102].

Individuals who desire a barrier or pericoital contraceptive – Barrier contraceptives (female and male condoms) and pericoital contraceptives (diaphragm, spermicidal sponge, cervical cap, or spermicide) do not interfere with oral EC function and can be started immediately. Use of these methods is discussed in detail elsewhere.

(See "Internal (formerly female) condoms".)

(See "External (formerly male) condoms".)

(See "Pericoital (on demand) contraception: Diaphragm, cervical cap, spermicides, and sponge".)

Can oral emergency contraception be a regular contraceptive method? — As the efficacy of repeated use of oral EC is generally lower than most contraceptives (figure 1), regular use of oral EC is not advised as a contraceptive method. Instead, we counsel patients about all available contraceptives and their use. However, pericoital EC is worthy of consideration for individuals who desire it. This means taking oral LNG immediately before or after each episode of intercourse. A meta-analysis of 11 trials that evaluated 0.75 mg LNG as a pericoital contraceptive reported a pooled Pearl Index of 5.4 pregnancies per 100 woman-years (95% CI 4.1-7.0) [103]. A subsequent study of 321 individuals using 1.5 mg LNG as a pericoital contraceptive (24 hours before or after intercourse) reported, for persons under 35 years of age, a Pearl Index of 10.3 per 100 woman-years (95% CI 5.4-19.9) with typical use and 11 (95% CI 5.7-13.1) for exclusive use [93].

FOLLOW-UP CARE

Routine counseling – Patients who use EC can anticipate their period within three weeks of initiating EC [6]. Onset of menses can be earlier or later than usual. Those who do not have a period within three weeks of EC use should perform a pregnancy test. While most do not require a specific follow-up visit, we advise patients to contact the office if they experience heavy bleeding with abdominal pain (concerning for ectopic pregnancy); have a positive pregnancy test; or have any concerns regarding lack of return of menses, bleeding, or any other questions.

Do users need a follow-up pregnancy test? – EC users who do not have menses within three weeks of taking oral EC should take a urine pregnancy test [6]. It is important to inform EC users that taking oral EC will not protect them against future risk of pregnancy from further intercourse in the current menstrual cycle. Those receiving an levonorgestrel (LNG) 52 mg intrauterine device (IUD) for EC will likely have irregular bleeding and should be informed to check a urine pregnancy test two to four weeks after IUD placement and at any time if pregnancy symptoms are present.

What if pregnancy occurs anyway? – It is possible that the pregnancy existed prior to taking EC, the EC failed, or a pregnancy resulted from additional intercourse after using EC. In all of these cases, oral EC has no known adverse effects on pregnancy [6]. Oral EC use has not been associated with congenital anomalies when pregnancy does occur [104,105]. EC use also does not appear to increase the risk of ectopic pregnancy should pregnancy occur. Should a pregnancy occur after IUD EC placement, the IUD should be removed and pregnancy options and counseling should be provided with linkage to desired care for abortion or pregnancy continuation. (See "Intrauterine contraception: Management of side effects and complications", section on 'Pregnancy'.)

Does EC use interfere with future fertility? – Use of oral Ecs does not negatively impact future fertility [6]. In general, the risk of ectopic pregnancy is reduced compared with females not using EC because the risk of pregnancy itself is reduced.

DRUG INTERACTIONS — Medications that induce the cytochrome P450 (CYP450) 3A hepatic enzyme (table 4) could theoretically reduce ulipristal acetate (UPA) or oral levonorgestrel (LNG) efficacy, but we do not have clinical and pharmacologic data to address this concern [68,80]. However, the manufacturer advises avoiding CYP450 3A inducers, such as rifampin, at the time of UPA administration because the plasma concentration of UPA is reduced [37]. The manufacturer packaging for oral LNG advises that use of efavirenz, rifampin, or the anti-seizure medications carbamazepine and phenytoin with LNG EC may reduce the EC efficacy [39]. However, for women taking CYP450 3A enzyme-inducing medication who desire EC, the British National Formulary and the Medicines and Healthcare products Regulatory Agency advise use of 3 mg oral LNG (twice the routine dose), although supporting data for this approach are lacking [80]. Until further data are available to inform clinical care in this situation, a reasonable approach is to double the dose of UPA or oral LNG for individuals using CYP450 3A-inducing medications, which is what the author does in his practice.

As the efficacy of the copper 380 mm2 or LNG intrauterine devices (IUDs) is not impacted by hepatic enzyme-inducing medication, these are the preferred EC methods for those who will accept an IUD.

SPECIAL POPULATIONS

Adolescents – Regardless of user age, all EC methods are safe [69]. Adolescents are capable of understanding and interpreting EC labels and instructions and tolerate oral levonorgestrel (LNG) [106,107]. Including EC information and ulipristal acetate (UPA) prescription, if desired, is appropriate family planning guidance for female and male adolescents. Information specific to adolescent patients can be found through the American Academy of Pediatrics document on Emergency Contraception, 2019.

Breastfeeding individuals – All EC methods are acceptable for use during lactation [22]. The Centers for Disease Control and Prevention's Medical Eligibility Criteria place no restriction on UPA use for breastfeeding persons, though they recommend expressing and discarding breast milk for 24 hours based on evidence of the drug in the milk of rats. There are no human data regarding infant UPA exposure. LNG passes into breast milk in minimal quantities. There are no contraindications to use of either intrauterine device (IUD) in breastfeeding individuals. (See "Contraception: Postpartum counseling and methods", section on 'Impact of contraception on breastfeeding'.)

ISSUES RELATED TO EMERGENCY CONTRACEPTION

Evolving complexities of delivering emergency contraception — Over the last few years, the clinical approach to EC has become more complicated. New methods have been developed, data have demonstrated decreased efficacy of oral EC methods for users with elevated body mass indices (BMIs), and ulipristal acetate (UPA) may decrease pregnancy protection for those persons starting a method of hormonal contraception along with EC. Constants also persist in this dynamic period. The copper 380 mm2 intrauterine device (IUD) remains the most effective method of EC and the only form of EC that provides ongoing highly effective contraception without additional action. It also remains true that people know when they need EC and can reliably use it safely. The use of oral EC still does not require a physical examination, pregnancy test, or laboratory tests [80]. Of course, it is still appropriate to offer future contraception to EC users and support for those who seek EC following sexual assault, as well as sensitivity to those who do not wish to discuss it.

Availability — Regardless of whether patients are directly requesting EC, they have a right to know about it and obtain it, if it can be helpful and they desire it. This includes being informed of the copper 380 mm2 IUD as the method with greatest efficacy and ability to provide ongoing contraception. However, education by itself is inadequate if the clinician does not have the ability to place IUDs when requested nor have a pathway for referral with same-day insertion for those without IUD insertion experience. Preventing undesired pregnancy is an emergency, as implied by the "E" in "EC" and should be treated accordingly.

In the United States, despite availability of multiple EC methods, there are a host of obstacles that EC users may encounter. While both brand name and generic forms of oral levonorgestrel (LNG) EC are available over the counter without age or gender restriction, there can be serious challenges to those attempting to obtain it. Research evaluating pharmacy user interactions have reported pharmacies not stocking the medication; keeping this over-the-counter medication in a locked location or behind the counter; employees providing incorrect information about restrictions; and high cost [108,109]. Additionally, UPA requires an interaction with a medical provider to acquire a prescription. A survey of 10 United States cities reported that only 10 percent of pharmacies actually carried UPA, though 72 percent had the ability to order it with a mean wait time of 24 hours [110]. The IUDs have a distinct set of obstacles, including need for a timely in-person visit, provision of a potentially uncomfortable insertion procedure, and the need for a provider capable of placing the device.

RESOURCES FOR PATIENTS AND CLINICIANS — The following resources are available in the public domain without cost.

International Consortium for Emergency Contraception provides several rigorously reviewed clinical publications by global experts including the definitive Emergency Contraceptive Pills: Medical and Service Delivery Guidance, Fourth Edition, 2018. They also provide country-by-country EC information, client information in several languages, and information on regional consortia (American, Latin American, African, European, and Arab).

Planned Parenthood provides resources for patients and clinicians on contraception and reproductive health care.

Bedsider.org is an online birth control support network for women ages 18 to 29.

The American College of Obstetricians and Gynecologists – FAQ 114 Emergency Contraception

The Faculty of Sexual & Reproductive Healthcare of the Royal College of Obstetricians and Gynaecologists Clinical Guideline – Emergency Contraception

The Guttmacher Institute provides information on United States laws and policies for EC

The American Academy of Pediatrics Policy Statement on Emergency Contraception, 2019

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Contraception".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they 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. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topics (see "Patient education: Emergency contraception (The Basics)")

Beyond the Basics topics (see "Patient education: Emergency contraception (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

What is emergency contraception? – Emergency contraception (EC) refers to products that prevent pregnancy from occurring after an episode of unprotected intercourse (UPI). EC works by disrupting the timing of ovulation or preventing fertilization of an ovulated egg; it is not an abortifacient (ie, abortion-inducing drug). (See 'What is emergency contraception and how does it work?' above and 'Mechanisms of action' above.)

What are the emergency contraception methods? – EC methods, in decreasing order of efficacy, include the copper 380 mm2 intrauterine device (IUD), levonorgestrel (LNG) 52 mg IUD, ulipristal acetate (UPA), oral LNG, and mifepristone (available outside the United States) (table 1). The other doses of LNG IUDs have not been studied for EC and thus should not be used. (See 'What are the emergency contraception methods?' above.)

How effective is emergency contraception? – When used for EC, the copper 380 mm2 and LNG 52 mg IUDs result in pregnancy rates of less than 1 percent. The oral medication EC methods UPA, oral LNG, and mifepristone have pregnancy rates of roughly 1 to 3 percent. (See 'How effective is emergency contraception at preventing pregnancy?' above.)

Which emergency contraception method should I pick?– Selection of an EC agent is driven by patient preference but must also consider method characteristics, need for ongoing contraception, method availability, and cost (algorithm 1).

IUD emergency contraception selection – For patients who desire an IUD for EC, we suggest a copper 380 mm2 IUD or an LNG 52 mg IUD rather than other hormonal IUDs (algorithm 1) (Grade 2C). Lower-dose LNG IUDs have not been studied for use as EC. Both the copper 380 mm2 and LNG 52 mg IUD are similarly effective, although supporting data for the LNG 52 mg IUD are limited. For individuals with a negative pregnancy test at the time of EC evaluation, the risk of pregnancy following an IUD insertion is low and likely lower than the risk associated with advising a patient to use oral EC followed by a backup contraceptive method and then IUD placement at a future date. Body weight or body mass index (BMI) does not impact the efficacy of either IUD. (See 'Intrauterine devices' above.)

Medication emergency contraception selection – For patients choosing medication EC, we suggest UPA rather than oral LNG (Grade 2B). UPA is the most effective oral method but requires a prescription and is not stocked by all pharmacies (algorithm 1). Oral LNG is the less effective oral agent but is available without a prescription and thus should be the easiest to obtain, which makes it a reasonable alternative. There are additional efficacy concerns for oral LNG in individuals with BMI ≥30 kg/m2. UPA or oral LNG for EC do not require a routine physical examination, pregnancy test, or laboratory tests. (See 'Oral medication emergency contraception methods' above and 'Emergency contraception efficacy' above.)

Original Yuzpe method of emergency contraception – Individuals who cannot access one of the EC methods above can use the Yuzpe method, which is two doses of combined oral contraceptives containing the equivalent of 100 to 120 mcg of ethinyl estradiol and 0.5 to 0.6 mg of LNG (or the equivalent) taken 12 hours apart. However, the efficacy of this approach is lower than that of standard EC methods. (See 'What are the emergency contraception methods?' above.)

Mifepristone – Where available, mifepristone 10 mg to 25 mg orally can be used for EC. Limited data suggest its efficacy is at least that of levonorgestrel and greater than that of the Yuzpe method. (See 'Oral medication emergency contraception methods' above.)

When to start contraception? – The future risk of pregnancy in patients presenting for EC highlights the need for initiating ongoing contraception for those with interest. The timing of contraceptive start and need for backup contraception or abstinence vary with the EC method (algorithm 1 and table 3). (See 'When to start contraception after emergency contraception' above.)

What patient groups or medications require additional consideration with emergency contraception? – All EC methods are safe for adolescents and lactating individuals. Medications that induce the cytochrome P450 (CYP450) 3A hepatic enzyme (table 4) could theoretically reduce UPA or LNG efficacy, but we do not have clinical and pharmacologic data to address this concern. (See 'Special populations' above and 'Drug interactions' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Mimi Zieman, MD, and Andrew Kaunitz, MD, who contributed to earlier versions of this topic review.

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Topic 5475 Version 119.0

References

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