Adolescent Health Care: A Practical Guide

Chapter 46

Emergency Contraception

Lisa M. Johnson

Melanie A. Gold

Emergency contraception (EC) has a tremendous potential to reduce the numbers of unplanned pregnancies and to decrease the need for abortion in women of all ages. It has been estimated that, with proper use, EC could prevent 1.7 million unplanned pregnancies and 800,000 abortions each year (Glasier and Baird 1998). EC use among women of all ages has increased from 17,000/year in 1995 to 634,000/year in 2002 and it remains an important pregnancy prevention measure because unprotected or poorly protected intercourse occurs at a higher rate from unanticipated intercourse (e.g., impulse, date, or rape), lack of perceived need for protection, and/or incorrect or inconsistent contraceptive use.

Emergency Contraception Methods

Three types of EC are available in the United States. The first two are hormonal methods that should be started within 120 hours (5 days) of exposure. The Yuzpe regimen, which has been available for >25 years, entails two doses of at least 100 µg ethinyl estradiol and 0.5 mg levonorgestrel (or 1.0 mg norgestrel) taken 12 hours apart. The progestin-only method entails either two single doses of 0.75 mg levonorgestrel (or 1.5 mg norgestrel) taken 12 hours apart or a single dose of 1.5 mg of levonorgestrel. The third method is insertion of a copper intrauterine device (IUD) within 5 days of unprotected intercourse.

The Yuzpe regimen, introduced in 1974, was the most commonly used EC method. Table 46.1 lists combination oral contraceptives that can be used to make up the Yuzpe regimen and their appropriate doses. In 1998, the U.S. Food and Drug Administration (FDA) approved the first dedicated EC product (Preven emergency contraceptive kit) using the Yuzpe regimen. Preven was taken off the market in 2004 when rights to the product were acquired by the company that makes the only current dedicated EC product (Plan B).

In 1999, the FDA approved a dedicated progestin-only product (Plan B), which contains two tablets each containing 0.75 mg of levonorgestrel. The FDA-approved instructions for Plan B are to take a single tablet as soon as possible after unprotected intercourse (up to 72 hours after coitus) and to take the second single tablet 12 hours later. More recently, von Hertzen et al. (2002) found that levonorgestrel could be given as a single dose of two tablets taken up to 120 hours after unprotected intercourse without causing any increase in side effects or decrease in efficacy. A progestin-only EC product should be used whenever possible because it is the current product of choice.

TABLE 46.1
Hormonal Emergency Contraception Regimens: Two Doses 12 Hours Apart




a Preferable to give both doses (two tablets) at once and can be given up to 120 hr after unprotected intercourse.

Progestin-only emergency contraceptive pills

Plan B


1 white tableta

Combination emergency contraceptive pills (Yuzpe regimen)



2 white tablets



5 pink tablets



5 orange tablets



5 orange tablets



5 pink tablets



4 light-orange tablets



4 white tablets



4 white tablets



4 white tablets



4 light-orange tablets



4 pink tablets



4 light-yellow tablets



4 light-yellow tablets



4 pink tablets

The progestin-only method of EC has several advantages over the Yuzpe method (Ho and Kwan, 1993; Task Force on Postovulatory Methods of Fertility Regulation, 1998). The efficacy of the progestin-only method is superior to that of the Yuzpe method (Table 46.2). Virtually every nonpregnant woman is eligible to use it, and side effects (especially gastrointestinal complaints such as


nausea and vomiting) occur significantly less often with the progestin-only method as compared to the Yuzpe regimen (Table 46.3).

TABLE 46.2
Comparative Efficacy of Combination Emergency Contraception (EC) Pills versus Progestin-Only EC Pills versus Copper Intrauterine Device Used for EC

EC Method

Combination EC Pills

rogestin-Only EC Pills

Copper IUD

EC, emergency contraception; IUD, intrauterine device.

Number of women




Number of pregnancies without EC




Number of pregnancies with EC




Percentage reduction




The third type of EC, the T-380A copper IUD (or Para-Gard), can be inserted up to 5 days after unprotected coitus and provides the best pregnancy protection. Although the copper IUD is more effective than the hormonal options for EC, it is rarely used for EC in female adolescents or among women who may be at risk for having a sexually transmitted infection (see Chapter 44 on IUD in adolescents). The copper IUD is also very expensive for single use for EC. Therefore, its use in the United States for this indication has been quite limited.

TABLE 46.3
Side Effects of Yuzpe Regimen versus Levonorgestrel (World Health Organization, 1998)


% with Symptom (95% Cl)


Side Effect

Yuzpe (n = 979)

Levonorgestrel (n = 977)


CI, confidence interval.
Based on women for whom full information was available.
a Mostly diarrhoea and some irregular bleeding or spotting.


50.5 (47.3–53.6)

23.1 (20.5–25.9)



18.8 (16.4–21.4)

5.6 (4.3–7.3)



16.7 (14.4–19.1)

11.2 (9.3–13.3)



28.5 (25.7–31.4)

16.9 (14.6–19.4)



20.2 (17.8–22.9)

16.8 (14.5–19.3)


Breast tenderness

12.1 (10.1–14.3)

10.8 (8.9–12.9)


Low abdominal pain

20.9 (18.4–23.6)

17.6 (15.3–20.1)


All other adverse effectsa

16.7 (14.4–19.1)

13.5 (11.4–15.8)


Several large studies conducted outside the United States found that when mifepristone is used for EC it is more effective than the Yuzpe regimen and equally effective as the progestin-only regimen (Ashok et al., 2002). There are very few side effects with low dose mifepristone used for EC; one study found the incidence of nausea was 1% (Ashok et al., 2004). When mifepristone is used for EC there is more of a delay in the timing of the next menstrual period than with other hormonal EC regimens. However, mifepristone is only available in the United States for use in medical abortions and off label use for EC is rare. Furthermore, studies have shown that 1/60th of the dose of mifepristone used for abortion (600 mg) is needed for EC (10 mg). No such 10 mg preparation is available in the United States, although mifepristone is used for EC in other parts of the world (Task Force on Postovulatory Methods of Fertility Regulation, 1999).


The expected pregnancy rate per single act of unprotected intercourse is estimated to be 8%. Efficacy for EC can be expressed in two ways—the observed pregnancy rate or the percentage reduction in the expected number of pregnancies (Table 46.2). For example, the single-use failure rate for the Yuzpe regimen is a little more than 3.2%, which represents a 75% reduction in expected pregnancies. Levonorgestrel alone is more effective, with a failure rate of only 1.1% (when compared with the Yuzpe regimen), which is an 89% reduction in the expected number of pregnancies (Lancet, 1998). The copper IUD is the most effective EC method currently available; its failure rate is 0.1%, which is a 99% reduction in the expected number of pregnancies. The estimates of overall efficacy for the Yuzpe regimen were calculated from a wide range of results observed in different


clinical trials. One trial found a 56% reduction in expected pregnancy rates with the Yuzpe regimen, while another found 89% (Trussell et al., 1999). In part, this variation may have reflected the inclusion of women who were already pregnant at the time they were treated. A recent, large-scale World Health Organization (WHO) trial demonstrated that the effectiveness of hormonal EC depends on how soon it is initiated after intercourse (Piaggio et al., 1999; Task Force on Postovulatory Methods of Fertility Regulation, 1998) (Table46.4), although earlier studies did not show such a temporal relationship (Trussell et al., 1996). In the WHO study, when hormonal EC was started within the first 12 hours, the pregnancy rate was 0.5% (a 94% reduction), but if the first dose was delayed until 60 to 72 hours after the exposure, the pregnancy rate was 4% (a 50% reduction). The 72-hour limit is expandable to 120 hours, but there is controversy over whether later use is associated with diminished protection. Some studies show no impact in efficacy based on timing whereas others do show a decline in efficacy with later use. In a 2003 study, 675 women using the Yuzpe regimen within 72 hours of unprotected intercourse were compared with 111 women using the Yuzpe regimen between 72 hours to 120 hours after unprotected intercourse; no statistically significant difference was found in failure rate between the two groups (Ellerston et al., 2003). However, the observation that earlier use of EC may be more efficacious has influenced prescribing patterns and led to the approval for behind-the-counter availability for people age 18 and over with government identification.

TABLE 46.4
Comparative Efficacy (Reduction in Pregnancy Rate) of Combination Emergency Contraceptive (EC) Pills versus Progestin-Only EC Pills over Various Time Periods

Time (hr)

Combination EC Pills (Yuzpe)

Progestin-Only EC Pills

 <24 hr



25–48 hr



49–72 hr



Mechanisms of Action

Hormonal methods of EC (Yuzpe or progestin-only) are approved by the FDA as contraceptives. This classification is supported by the observations (a) that most conceptions occur when intercourse precedes ovulation and (b) that EC with oral contraceptives is more effective when administered early after coitus. The primary action of the hormonal methods of EC appears to be delaying or inhibiting ovulation, but new analysis suggests that other mechanisms may be important (Trussell and Raymond, 1999). Studies have found that levonorgestrel and the Yuzpe regimen suppress or delay the luteinizing hormone (LH) peak and inhibit follicle rupture (Croxatto et al., 2003; Marions et al., 2004). EC may also alter tubal motility, production of progesterone by the corpus luteum, and the composition of the endometrium to block implantation (Glasier, 1997).

Although it may not always be clear whether oral EC is working by delaying ovulation or impeding implantation, EC does not work as an abortifacient. EC taken after a pregnancy has been established to have no effect; it will not cause a miscarriage, and it will not increase the risk of fetal malformations (Raman-Wilms et al., 1995; Blumenthal and McIntosh, 1996). EC is contraindicated in pregnancy because it is ineffective once implantation of a fertilized egg has occurred.

The mechanisms of action for the copper IUD as a postcoital method have not been well elucidated. It is unclear how important the copper ions are to the copper IUD's contraceptive effect when used as an EC (Rivera et al., 1999). Because sperm can live in the cervical canal for up to 5 days before fertilization, the spermicidal action of the copper IUD could be important. The presence of a foreign body (the IUD) may alter the endometrium and prevent implantation.


EC is indicated any time a woman of reproductive age wishes to lower her risk of becoming pregnant following unprotected intercourse (e.g., following sexual assault or unplanned intercourse.) EC is also indicated after inadequately protected sexual intercourse from failure or misuse of a contraceptive method (Table 46.5).


Yuzpe Method

The FDA labeling for combination oral contraceptives used for EC includes the same contraindications as when combination oral contraceptives are taken on a daily basis (see Chapter 43). However, approximately four decades of use has shown that such stringent restrictions for a single use of the Yuzpe regimen are not necessary. Current pregnancy, allergy, and acute current migraine with neurological deficits are the only absolute contraindications to prescribing the Yuzpe regimen. A history of previous thrombosis should not be a contraindication to a single course of the Yuzpe regimen (Webb and Tabemer, 1993), although, if available, progestin-only pills would be preferable for medicolegal reasons in addition to being more effective and having fewer side effects compared with the Yuzpe regimen. The risk of a clot for a patient with prior history of deep vein thrombosis (DVT) or pulmonary embolism (PE) remains higher in pregnancy than for a single course of the Yuzpe regimen.

Progestin-Only Method

The three contraindications for progestin-only oral contraceptives including Plan B are:

  1. Pregnancy
  2. Hypersensitivity to any component of product
  3. Undiagnosed abnormal genital bleeding

However, in an adolescent who is having abnormal genital bleeding, as long as pregnancy is ruled out, EC can


be given. The progestin-only method is preferred for breast-feeding women because the estrogen in the Yuzpe regimen has the potential to decrease breast milk production.

TABLE 46.5
Indications for Using Emergency Contraception


Reason for Failure

Anytime sex is unprotected

Nothing used, sexual assault


Breaks or slips

Combination oral contraceptive pills (COCs)

Started the pill within the last 7 d (but not during menses), and did not use a back up or back up failed


Missed two or more pills in a row during the first 3 wk of any pack of pills


More than 2 d late in starting a new pack of pills after 7 d of placebo pills

Progestin-only oral contraceptive pills (POPs)

Started the pill within the past 2 d (but not during menses), and did not use a back up or back up failed


Missed 1 or more pills in any row of the pack


More than 1 d late in starting a new pack of pills

Transdermal patch (Ortho-Evra) (Ortho-McNeil, Raritan, NJ)

Started the patch within the past 7 d (but not during menses), and did not use a back up or back up failed


Patch off >24 hr during patch-on wk


Left patch on for >9dstraight


>2 d late in putting new patch on after patch-off wk

Vaginal contraceptive ring (NuvaRing)(Organon, Roseland, NJ)

Started the ring within the past 7 d (but not during menses), and did not use a back up or back up failed


Taken out for >3 hr during ring-in wk


Left in >5 wk in a row


>2 d late in putting new ring in after ring-out wk

Depot medroxyprogesterone acetate injection (Depo-Provera) (Pfizer, New York, NY)

Started Depo-Provera within the last 14 d (but not within 5 d of menses), and did not use a back up or back up failed


More than 13 wk since got last Depo-Provera shot

Diaphragm or cervical cap

Slipped during intercourse


Removed too early after intercourse (<6h)


Did not wipe off tip of penis before vaginal penetration


Ejaculation occurred while penis was inside the vagina


Put in more than an hour before intercourse


Dose not repeated before subsequent episodes of intercourse


Any time used without another back up (like a condom)

Copper Intrauterine Device Method

The copper IUD for long-term has several contraindications (see Chapter 44 on IUDs). Because short-term use cannot be ensured, these same contraindications have been applied to the use of the copper IUD for EC.

Side Effects

Side effects of the Yuzpe regimen and progestin-only EC are largely hormone related and can last for 2 to 3 days. The most common side effects are gastrointestinal. With the Yuzpe method, 30% to 66% of women report nausea, and 12% to 22% have vomiting. Gastrointestinal complaints can be reduced by routinely giving a long-acting antiemetic over-the-counter (OTC) agent such as meclizine 50 mg 1 hour before the first EC dose. Raymond et al. (2000) found that meclizine can halve the risk of nausea and vomiting, but most women experience drowsiness. The progestin-only method has a lower incidence of gastrointestinal side effects; only 23% of women report nausea, 6% vomiting, and 5% report diarrhea, therefore antiemetics are not routinely offered when prescribing progestin-only EC.

Other hormone-related side effects include breast tenderness, headache, abdominal bloating, fatigue, and dizziness. Among women who took the Yuzpe regimen, 10% had vaginal spotting at some point before the next menses which usually lasted 1 to 2 days. There was no difference in spotting rates between women who became pregnant following EC use and those who did not. Women who took EC in the first half of the menstrual cycle (before day 12) were more likely to have their next period earlier than expected (by >3 days) (Webb et al., 2004). Depending on when in the cycle EC is used, the timing and flow of


the next menses may be altered. However, 98% of women should have menstrual bleeding within 3 weeks of EC use; if an EC user has not started menses 3 weeks after EC use, she should get a pregnancy test. Some adolescent health care providers recommend a pregnancy test 14 days after EC use, regardless of menses.

Management Issues

  1. Advance prescription: Until recently, EC was administered primarily on an as-needed basis after unprotected intercourse. However, the most effective way to provide EC is in advance of need. Advance provision of EC may increase immediate use and enhance efficacy. Glasier and Baird (1998) found that women who had EC available at home were 74% more likely to use it than those who had to obtain EC on demand at a clinic. Raine et al. (2000) found that those who had EC in advance tripled their use of it. Gold et al. (2004b)found that adolescents 15 to 20 years old were nearly twice as likely to use EC if they had it in advance and they used EC sooner after unprotected intercourse compared with the control group. In seven of the eight advance provision studies to date, female adolescents and adults who got advance provision of EC did not have higher rates of unprotected intercourse and did not reduce their use of ongoing contraception compared with those in the control groups (Glasier and Baird, 1998; Lovvorn et al., 2000; Ellertson et al., 2001;Jackson et al., 2003; Lo et al., 2004; Gold et al., 2004b; Raine et al., 2005).
  2. Education: EC should be discussed during routine office visits with both male and female adolescents who want to avoid pregnancy (Gold et al., 2004a).
  3. Assessment: A woman who presents for EC after unprotected intercourse needs minimal assessment. It is prudent to record her last menstrual period, the number and timing of any previous acts of intercourse (protected or not) during the cycle, any symptoms of pregnancy, prior experience with EC or birth control pills, and any contraindications to EC that she may have. No physical examination is needed. Patients can be rescheduled for routine gynecological care such as a Pap smear or sexually transmitted disease (STD) testing if they are asymptomatic for a current STD. No laboratory tests are mandatory, although some providers do a sensitive urine pregnancy test in the office if there is any question about whether the patient might already be pregnant. Many practitioners prescribe EC for patients after telephone triage. To date, pharmacists in several states can provide EC without a prescription. In Alaska, Hawaii, and Washington State pharmacists have collaborative practice agreements, specifically for E In California, Maine, and New Mexico pharmacists have independent prescribing authority for EC. Other states, including Massachusetts, have recently passed legislation in favor of similar pharmacist agreements.
  4. Multiple doses: Women who present with multiple episodes of unprotected intercourse can be provided EC for their last coital exposure if they are not pregnant. In addition, there is no absolute limit to the number of times EC can be used within one cycle or within a particular time frame, if there is need. However, women who are using EC frequently should be advised that other birth control methods are more effective in the long run.
  5. Dosing by timing in cycle when coitus occurred: Because of variations in menstrual cycle length and the long life span of sperm, unprotected intercourse at any time in the cycle may warrant EC protection.
  6. EC is a standard of care: Courts have ruled that EC is a community standard of care for women who have been exposed to potential unintended pregnancy (especially for sexual assault victims) (Brownfield v. Daniel Free-man Marina Hospital, 1989). Other authorities, such as the American College of Obstetricians and Gynecologists (2005), have reconfirmed that postcoital contraception is standard of care. Likewise, the Society for Adolescent Medicine and the American Academy of Pediatrics have published statements confirming that EC is a standard of care for adolescents (Gold et al., 2004a; AAP EC Policy Statement,
  7. Contraception after EC: Ongoing methods of birth control may be started or restarted immediately after using E Daily use of oral contraceptives, the Ortho-Evra patch or the NuvaRing can be started the same day that either the Yuzpe regimen or Plan B is taken or can be started 24 hours later. Patients should be prescribed a single cycle of contraception and asked to return 2 weeks after their EC dose for a urine pregnancy test and for subsequent supply of contraception. Depot medroxyprogesterone acetate (DMPA or Depo-Provera) can be administered the same day EC is taken if the patient understands and accepts the uncertainty of the impact her contraceptive will have on her next menses, and if she agrees to return for routine pregnancy testing in 10 to 14 days. Appropriate backup methods should be provided for the first cycle. Women who have a copper IUD inserted are provided with both EC and ongoing contraceptive protection.

Management of Side Effects

  1. Nausea and vomiting
  2. Symptoms can be reduced by using progestin-only EC such as Plan B or by prescribing a long-acting antiemetic 1 hour before starting the Yuzpe method (Raymond et al., 2000).
  3. The nausea and vomiting do not result from gastric irritation but rather from central nervous system stimulation. Therefore, the first dose of EC should be repeated only if the vomiting occurs within 30 to 60 minutes of ingestion of the first dose. Most experts also recommend repeat administration of the second dose if the patient vomits it within 30 minutes, although the importance of the second dose has recently been questioned (Ellertson et al., 2003).
  4. Change in menstrual flow: Approximately 13% of women experienced heavier flow and the same percentage had lighter flow after EC use. Most have their next menses at the expected time or a few days early or late (Task Force on Postovulatory Methods of Fertility Regulation, 1998).
  5. Amenorrhea: A woman who does not menstruate within 21 days of taking EC should be tested for pregnancy. If she is pregnant, she should be reassured that taking EC will not adversely affect her fetus or the pregnancy. If she is not pregnant, watchful waiting for return to normal cycling is appropriate for up to 3 months, but contraception should be offered.



Access Issues

  1. Provider issues: EC is remarkably cost-effective. Routine advance prescription of EC to women who rely upon male condoms as their only contraceptive saves the health system $263 per user in managed care systems and $99 in public sector settings (Trussell et al., 1997). Nevertheless, EC remains underutilized in the United States. Studies show that obstetrician-gynecologists, emergency room physicians, and general practitioners are very aware of EC, and most feel comfortable prescribing it. However, the average number of prescriptions written each year by the most actively prescribing doctors is only approximately 5.5 (Delbanco et al., 1997). Most physicians prescribe EC only for victims of sexual assault. A Kaiser survey in 1999 found that 83% of obstetrician-gynecologists prescribed EC in the past year, but 52% had written only one to five prescriptions for it within the last year, whereas 37% of family practitioners prescribed EC in the last year, with more than half prescribing it only one to five times. Only 17% of family practitioners and 31% of obstetrician-gynecologists had written six or more prescriptions for EC in the preceding 12 months (Henry J. Kaiser Family Foundation, 2000). A survey of pediatricians found that knowledge deficits, not attitude-related variables, were associated with low EC use and counseling (Sills et al., 2000). Gold et al. (1997) found that 88% of adolescent health experts said they would prescribe EC to teens, but 12% were concerned that doing so would encourage contraceptive risk taking; 29% believed that repeated EC use could pose a health threat; and 56% would not prescribe EC in advance of need. More recently, Rowlands et al. (2000) found that 5% of 14- to 29-year olds in Britain received EC each year, and only 4% reported using it more than twice in any year.
  2. Patient issues: Many physicians justify under-prescribing EC by noting that women do not ask for it. This reflects that, until recently, few women knew that EC was available. Surveys of adult American women found that only 40% were aware of EC and even fewer adolescents (25%) had ever heard about it (Delbanco et al., 1997; Delbanco et al., 1998). However, awareness is rising. In 2002, Aiken et al., compared the awareness, attitudes, and perceived barriers to using EC among a sample of young women from 1996 with a different sample of women from 2002. Between 1996 and 2002, the percentage of participants reporting that they ever heard of EC grew from 44% to 73% (Aiken et al., 2005). Public service campaigns and articles in teen and women's magazines have highlighted the availability of E Special episodes of popular television shows (e.g., “ER,” “Law & Order: Special Victims Unit”) and MTV have featured the use and availability of EC.
  3. Pharmacy issues: Pharmacies in many areas of the country refuse to carry EC because of their confusion about its mechanisms of action (Cohen, 1999). Some states have passed “conscience clauses” that provide a legal basis for this refusal practice. Other pharmacists and pharmacy chains claim that their decisions are based on economic factors—that the demand for EC is too low to justify the cost of the shelf space. The need for advance prescriptions is particularly critical in these settings. It may take a patient several days to locate a pharmacy with Plan B—hours that may decrease efficacy. If a patient presents after unprotected intercourse for EC and it is known that she may encounter problems filling a prescription for Plan B, it may be prudent to use one of the standard Yuzpe regimens (Table 46.1), with prescription instructions to “take as directed,” while providing the patient with specific EC instructions.

Patients can learn the names and addresses of local providers of EC by accessing the EC hotline, either by telephone at 1-888-NOT-2-LATE (Trussell et al., 1998) or on the Internet at Physicians and clinics can contact these same hotlines to join the network of EC providers.

Some European countries and recently Canada have allowed levonorgestrel EC to be sold as an OTC medication. After a 3 year delay, the FDA approved OTC sales of Plan B in August 2006 to individuals ages 18 years and older. However, Plan B remains prescribtion-only status for female adolescents ages 17 years and under. There is ongoing lobbying of the FDA to extend OTC access of Plan B to adolescents under the age of 18.

Web Sites

For Teenagers and Parents

EC Web site from Office of Population Research with list of providers, information, news, EC availability by country, and references:

EC information from the Planned Parenthood Federation of America:

Duke University Student Health Center information site on EC:

Duke University Student Health Center information site on Sexual Health:

Women's Capital Corporation Web site for Plan B:

Boston Children's Hospital website with EC information:

For Health Professionals

American Academy of Pediatrics Policy Statement on EC, Fact Sheet for Parents and Adolescents, and Speaking Points for Pediatricians: (Policy Statement and Fact Sheet) (Speaking Points for Pediatricians at AAP member center)

Information about EC and directory of providers on the internet:

Toll-free telephone information about EC and provider referrals 1-888-NOT-2-LATE (English and Spanish instructions)

Information about enrolling as a provider in the U.S. directory

EC and other information about contraception:



EC information from the Planned Parenthood Federation of America

Article from Hospital Practice on EC:

Sites to download PowerPoint presentation on EC from Association of Reproductive Health Professionals: and

References and Additional Readings

Aiken AM, Gold MA, Parker AM. Changes in young women's awareness, attitudes, and perceived barriers to using emergency contraception. J Pediatr Adolesc Gynecol2005;18(1):25.

American College of Obstetricians and Gynecologists. ACOG practice bulletin: clinical management guidelines for obstetricians-gynecologists: emergency contraception. No. 69, December 2005. (Replaces No. 25, March 2001). Obstet Gynecol 2005;106(6):1443.

Ashok PW, Hamoda H, Flett GM, et al. Mifepristone versus the Yuzpe regimen (PC4) for emergency contraception. Int J Gynaecol Obstet 2004;87(2):188.

Ashok PW, Stalder C, Wagaarachchi PT, et al. A randomised study comparing a low dose of mifepristone and the Yuzpe regimen for emergency contraception. Br J Obstet Gynaecol 2002;109(5):553.

Blumenthal P, McIntosh N. Emergency contraception. In: Oliveras E, ed. Pocket guide for family planning service providers, 3rd ed. Baltimore: JHPIEGO Corporation, 1996:65.

Brownfield v. Daniel Freeman Marina Hospital. No. B032109. Court of Appeals of California, Second Appellate District, Division Four, 208 Cal. App. 3d 405; 1989 Cal. App. LEXIS 157;256 Cal. Rptr. 240. March 2, 1989.

Cohen SA. Objections, confusion among pharmacists threaten access to emergency contraception. Guttmacher Rep Public Policy 1999;2:1.

Conard LE, Gold MA. Emergency contraception update: providing emergency contraception in the pediatrician's office. Contemp Pediatr 2006;23(2):49.

Croxatto HB, Oritz ME, Müller AL. Mechanisms of action of emergency contraception. Steroids 2003;68:1095.

Delbanco SF, Mauldon J, Smith MD. Little knowledge and limited practice: emergency contraceptive pills, the public, and the obstetrician-gynecologist. Obstet Gynecol1997;89:1006.

Delbanco SF, Parker ML, McIntosh M, et al. Missed opportunities: teenagers and emergency contraception. Arch Pediatr Adolesc Med 1998;152:727.

Ellertson C, Ambardekar S, Hedley A, et al. Emergency contraception: randomized comparison of advance provision and information only. Obstet Gynecol 2001;98(4):570.

Ellertson C, Webb A, Blanchard K, et al. Modifying the Yuzpe regimen of emergency contraception: a multicenter randomized controlled trial. Obstet Gynecol 2003;101(6):1160.

Glasier A. Emergency postcoital contraception. N Engl J Med 1997;337:1058.

Glasier A, Baird D. The effects of self-administering emergency contraception. N Engl J Med 1998;339:1.

Gold MA, Schein A, Coupey SM. Emergency contraception: a national survey of adolescent health experts. Fam Plann Perspect 1997;29:15.

Gold MA, Sucato G, Conard LE, et al. Provision of emergency contraception to adolescents: position paper of the Society for Adolescent Medicine. J Adolesc Health 2004a;35:66.

Gold MA, Wolford JE, Smith KA, et al. The effects of advance provision of emergency contraception on adolescent women's sexual and contraceptive behaviors. J Pediatr Adolesc Gynecol 2004b;17:87.

Henry J. Kaiser Family Foundation. National survey of health care providers on emergency contraception, 2000. MenloPark, CA: Kaiser Family Foundation, 2000.

von Hertzen H, Piaggio G, Ding J, et al. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomized trial. Lancet2002; 360:1803–1810.

Ho PC, Kwan MS. A prospective randomized comparison of levonorgestrel with the Yuzpe regimen in post-coital contraception. Hum Reprod 1993;8:389.

Jackson RA, Schwarz EB, Freedman L, et al. Advance supply of emergency contraception: effect on use and usual contraception—a randomized trial. Obstet Gynecol2003;102(1):8.

Lo SST, Fan SYS, Ho PC, et al. Effect of advanced provision of emergency contraception on women's contraceptive behaviour: a randomized controlled trial. Hum Reprod 2004; 19(10):2404.

Lovvorn A, Nerquaye-Tetteh J, Glover EK, et al. Provision of emergency contraceptive pills to spermicide users in Ghana. Contraception 2000;61:287.

Marions L, Cekan SZ, Bygdeman M, et al. Effect of emergency contraception with levonorgestrel or mifepristone on ovarian function. Contraception 2004;69:373.

Piaggio G, von Hertzen H, Grimes DA, et al. Task Force on Postovulatory Methods of Fertility Regulation. Timing of emergency contraception with levonorgestrel or the Yuzpe regimen. Lancet 1999;353:721.

Raine T, Harper C, Leon K, et al. Emergency contraception: advance provision in a young, high-risk clinic population. Obstet Gynecol 2000;96:1.

Raine TR, Harper CC, Rocca CH, et al. Direct access to emergency contraception through pharmacies and effect on contraception and STDs: a randomized controlled trial. JAMA2005;293:54.

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