[15][16][17] Progestin-only ECPs are available over-the-counter (OTC) in many countries (e.g. Australia, Bangladesh, Bulgaria, Canada, Cyprus, Czech Republic, Denmark, Estonia, India, Malta, Netherlands, Norway, Portugal, Romania, Slovakia, South Africa, Sweden, United States), from a pharmacist without a prescription, and available with a prescription in some other countries.

[29] A review found that a moderate dose of mifepristone is better than LNG or Yuzpe, with delayed return of menstruation being the main adverse effect of most regimes.

[33][35] Other common side effects (each reported by less than 20% of levonorgestrel-only users in both the 1998 and 2002 WHO trials) were abdominal pain, fatigue, headache, dizziness, and breast tenderness.

[13][48][49] The herbal preparation of St John's wort and some enzyme-inducing drugs (e.g. anticonvulsants or rifampicin) may reduce the effectiveness of ECP, and a larger dose may be required,[33][50] especially in women who weigh more than 165 lbs.

[57] ECPs are generally recommended for backup or "emergency" use – for example, if a woman has forgotten to take a birth control pill or when a condom is torn during sex.

[6] While they are effective for individuals who use them in a timely fashion, the availability of EC pills does not appear to decrease abortion rates at the population level.

[1] In 2012 the American Academy of Pediatrics (AAP) stated: "Despite multiple studies showing no increased risk behaviour and evidence that hormonal emergency contraception will not disrupt an established pregnancy, public and medical discourse reflects that personal values of physicians and pharmacists continue to affect emergency-contraception access, particularly for adolescents.

[68] In March 2011, the International Federation of Gynecology and Obstetrics (FIGO) issued a statement that: "review of the evidence suggests that LNG [levonorgestreol] ECPs cannot prevent implantation of a fertilized egg.

"[68][71] In June 2012, a New York Times editorial called on the FDA to remove from the label the unsupported suggestion that levonorgestrel emergency contraceptive pills inhibit implantation.

[72] In November 2013, the European Medicines Agency (EMA) approved a change to the label for HRA Pharma's NorLevo saying it cannot prevent implantation of a fertilized egg.

[73] Progestogen-only emergency contraceptive does not appear to affect the function of the fallopian tubes or increase the rate of ectopic pregnancies.

[47] The primary mechanism of action of progesterone receptor modulator emergency contraceptive pills like low-dose and mid-dose mifepristone and ulipristal acetate is to prevent fertilization by inhibition or delay of ovulation.

"[68][75][76] The primary mechanism of action of copper-releasing intrauterine devices (IUDs) as emergency contraceptives is to prevent fertilization because of copper toxicity to sperm and ova.

[4][33][65] In 1966, gynecologist John McLean Morris and biologist Gertrude Van Wagenen at the Yale School of Medicine, reported the successful use of oral high-dose estrogen pills as post-coital contraceptives in women and rhesus macaque monkeys, respectively.

"[91] After the WHO conducted a large trial comparing Yuzpe and levonorgestrel in 1998,[25][92] combined estrogen-progestin products were gradually withdrawn from some markets (Preven in the United States discontinued May 2004, Schering PC4 in the UK discontinued October 2001, and Tetragynon in France) in favor of progestin-only EC, although prescription-only dedicated Yuzpe regimen products are still available in some countries.

In their February 2014 emergency review article, Trussell and Raymond note: Calculation of effectiveness, and particularly the denominator of the fraction, involves many assumptions that are difficult to validate.

Roe v. Wade caused a historical survey to be conducted and concluded that right to privacy cases such as Griswold v. Connecticut allowed women to have parental control over childrearing, including the use of contraception for reproductive autonomy.

[120] Since the late 1990s, due to rights given by specific policies, the dispensation of emergency contraceptives on issues of religious and moral objections of providing care has extended from doctors, nurses, and hospitals to pharmacies and individual pharmacists.

In other states, women have been allowed various amounts of access, including the ability to access EC without a prescription from a physician, creation of policies limiting the ability of pharmacists to deny EC on religious and moral grounds, and creation of policies discouraging pharmacists from denying to fill contraceptive prescriptions.

[121] Under federal law, a provision of the Affordable Care Act of 2010 has guaranteed coverage of contraceptives, applying to most private health plans nationwide.

[122] In October 2017, however, the Trump administration made it easier for employers that offer health care plans to exclude contraceptive coverage.

This topic continues to be fought upon on different levels; for example, Stormans, Inc v Wiesman challenged Washington state regulations on providing all lawfully prescribed pharmaceuticals, including EC.

[123] Courts have been warned that if pharmacists are allowed to deny EC prescriptions on religious or moral beliefs, it can affect public health and set a dangerous precedent with respect to "critical, life-saving preventative care".

[125] Mechanism of actionCopper-releasing IUCsWhen used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization.

Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health79 and the American College of Obstetricians and Gynecologists (ACOG).80Ulipristal acetate (UPA).

Several clinical studies have shown that combined ECPs containing ethinylestradiol and levonorgestrel can inhibit or delay ovulation.107–110How does EC work?In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation.8 The possible mechanisms of action should be explained to the patient as some methods may not be acceptable, depending on individual beliefs about the onset of pregnancy and abortion.Copper-bearing intrauterine device (Cu-IUD).

The failure rate (in a small number of studies) is very low, 0.1%.34,35 This method definitely prevents implantation, but it is not suitable for women who are not candidates for intrauterine contraception, e.g., multiple sexual partners or a rape victim.

Levonorgestrel emergency contraception does not affect implantation and is not abortifacient.Intrauterine insertion of a copper IUD within 5 to 10 days of midcycle coitus is a very effective method of preventing continuation of the pregnancy...

In 2009, European regulatory approval was granted for a 30-mg tablet of ulipristal (under the brand name of EllaOne) as an emergency contraceptive pill for use up to 5 days after unprotected intercourse.

An application for approval in the United States is under review.Levonorgestrel-only emergency contraceptive pills:• Interfere with the process of ovulation;• May possibly prevent the sperm and the egg from meeting.Implications of the research:• Inhibition or delay of ovulation is LNG ECPs principal and possibly the only mechanism of action.• Review of the evidence suggests that LNG ECPs cannot prevent the implantation of a fertilized egg.