Emergency contraception (EC) describes the use of contraceptive measures to prevent pregnancy occurring after intercourse has taken place.

In the UK three forms of EC are currently recommended:

• An oral progestogen-only emergency contraceptive (POEC) - levonorgestrel (LNG).
• A selective progesterone receptor modulator (SPRM) - ulipristal acetate.¹
• A copper intrauterine contraceptive device (IUCD).

Combined oestrogen and progesterone preparations were previously used; however, a large randomised study showed increased effectiveness and acceptability of POEC which has now been adopted as the method of choice.²

Mifepristone may also be used for EC but is not licensed for this use in the UK.^3,4

Important points to note about EC are that:

• It is not considered an abortifactant (a Judicial Review in 2002 ruled that pregnancy begins at implantation, not at fertilisation).⁵
• There is no time in the menstrual cycle when there is no risk of pregnancy following unprotected sexual intercourse (UPSI), particularly in an irregular cycle. Conception has been recorded as occurring on all days in a cycle, but is least likely to occur in the first three days.⁵
• A cu-IUCD is the most effective form of EC and should be offered to all women, even if they present within 72 hours.

Indications for emergency contraception

When no contraception has been used

• Following consensual sexual intercourse.
• Following rape or sexual assault.

When there is contraceptive failure or incorrect use

• Incorrect use or failure of barrier methods such as the condom, diaphragm or cap.
• Failed coitus interruptus (ejaculation into vagina or on to external genitalia).
• Miscalculation of the periodic abstinence method or failure to abstain during the fertile period.
• IUCD/intrauterine system (IUS) expulsion (if complete or partial expulsion has occurred or if it is necessary to remove the device mid-cycle and there has been unprotected sexual intercourse (UPSI) within the previous seven days).⁵
• Whilst using any form of hormonal contraception if intercourse has occurred whilst taking, or within 28 days after taking, enzyme-inducing agents, e.g. rifampicin, and if no additional barrier methods have been used.
• Following incorrect use or potential failure of hormonal method of contraception as outlined below.⁵

Factors in choosing the type of emergency contraception

Before making a shared decision with the patient as to the appropriate form of emergency contraception (EC), a full history should be taken with particular reference to:

• Elapsed time since unprotected intercourse.
• What contraception was used at the time of intercourse, if any.
• Menstrual history:
  • Date of last menstrual period.
  • Was the last period normal?
  • Usual cycle length.
  • Is ovulation likely to have taken place yet this cycle? (If the normal cycle is 28 days, ovulation is thought to occur around day 14).
  • Could implantation of a fertilised ovum have occurred this cycle? (Implantation occurs no earlier than five days after ovulation.⁶ To calculate the likely date of implantation, subtract 14 days from the date of the expected date of the next period and add five days).
• Any other unprotected intercourse this cycle? Could the woman already be pregnant?
• Any previous use of EC?
• Obstetric and gynaecological history (with particular attention to history of pelvic inflammatory disease (PID), current vaginal discharge, history of ectopic pregnancy).
• Current requirement for contraception.
• Medications used, e.g. enzyme-inducing agents such as phenytoin (don't forget over-the-counter enzyme inducers such as St.John's wort).
• General health, looking for any contra-indications, e.g. liver disease, porphyria.
• Sexual history - consider the risk of sexually transmitted infection (STI).

Progestogen-only emergency contraception

Mode of action

• When used early in the cycle, it is thought that progestogen-only emergency contraception (POEC) inhibits ovulation. When used later in the cycle, it is unclear how it has its effect.⁵

Prescribing

• POEC should be given in the form of levonorgestrel 1.5 mg, taken as soon as possible after unprotected sexual intercourse (UPSI).
• It is now available to buy over-the-counter without prescription for those aged 16 years or more, in addition to being a prescribable drug.
• Levonelle® 1500 or Levonelle® One Step is a single 1.5 mg dose (World Health Organization (WHO) recommended regimen).⁷

Timing of use

• Licensed for use within 72 hours of UPSI.
• POEC can be used more than once in a cycle if appropriate and repeated use will not induce abortion if the woman is already pregnant. This is supported by the Faculty of Sexual and Reproductive Healthcare.⁵

Efficacy

• 84% of expected pregnancies are prevented if levonorgestrel emergency contraception (LNG-EC) is used within 72 hours of UPSI.⁵
• The closer to the episode of UPSI that LNG-EC is taken, the more effective it is.
• Results from a WHO trial in 1998 showed that levonorgestrel, taken as two 750 microgram doses with a 12-hour interval (the old regime), is 95% effective if taken within 24 hours of unprotected sex, 85% effective between 25-48 hours and 58% effective if taken between 49-72 hours.²
• Some practitioners do use LNG-EC (outside its licence) between 73 and 120 hours after UPSI if an IUCD is not appropriate or wanted. If used in this timescale, 63% of expected pregnancies are prevented, i.e. the failure rate rises.⁵
• Women who are taking enzyme-inducing drugs, e.g. phenytoin, rifampicin, tropicamide, will be at risk of a higher failure rate. They should be advised that the IUCD is a more reliable method for them. If they choose to take LNG-EC, they should take 2 x 1.5 mg tablets as a single dose. This is outside the licence for the drug and they should be informed of this.⁵
• No increase in dose is necessary if women are taking non-enzyme-inducing antibiotics.⁵

Contra-indications^8,9

• Hypersensitivity to levonorgestrel.
• Acute porphyria.
• Caution is recommended in severe liver disease.
• Severe malabsorption syndromes (e.g. Crohn's disease) might impair the efficacy of LNG-EC.
• Rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption (preparations contain lactose).

Side-effects

• Nausea
• Vomiting

Specific advice for women using LNG-EC

• If vomiting occurs within 2 hours of taking LNG-EC, a repeat dose is needed. Re-attend or call NHS Direct if vomiting occurs (1% of women).¹⁰
• Use another form of contraception, e.g. condoms, for the remainder of the cycle.
• If emergency contraception is used because of missed oral contraceptive pills, women should be advised to resume their normal pill-taking regime within 12 hours of taking LNG-EC.
• There is no current evidence that POEC affects an existing pregnancy.^8,9

Selective progesterone receptor modulator - ulipristal acetate

This method has been available in the UK since October 2009 as ellaOne®. It is a second-generation selective progesterone receptor modulator (SPRM) - mifepristone is a first-generation SPRM - and is the only oral choice for UPSI between 72 and 120 hours.

Mode of action

It inhibits or delays ovulation. A single dose in the mid-follicular phase has been shown to suppress the further development of follicles. If given around the time of the luteinising hormone surge, the rupture of follicles is inhibited. Administration later in the cycle affects changes in the endometrium which make implantation less likely.¹¹

Prescribing

It consists of one tablet (30 mg) of ulipristal acetate which should be taken as soon as possible after UPSI, but within 120 hours of the event.

Timing of use

It has been shown to be effective up to 120 hours after unprotected sexual intercourse, or failure of the normal contraceptive method.

Efficacy

Pregnancy rates with ulipristal are around 1-2% when taken within 120 hours.¹² There are data to show performance comparable to POEC and potentially more effective.

Efficacy may be reduced when the woman is taking liver enzyme-inducing medication, or medication which raises normal gastric pH.

Contra-indications

Pregnancy or suspected pregnancy should be excluded before ulipristal is prescribed. There is insufficient research to advise safely on breast-feeding and it is therefore recommended that breast-feeding is best avoided for 36 hours after a dose has been taken.

Severe liver disease or uncontrolled asthma are also contra-indications to its use.

Side-effects

These are similar to POEC. The most commonly observed problems are abdominal cramps and irregular menstrual bleeding.

Cost-effectiveness

It is more expensive than POEC, but may be cost-effective in the 72- to 120-hour window.¹³

Intrauterine contraceptive devices

Mode of action

• It is thought that IUCDs have an inhibitory effect on both fertilisation and implantation.
• Fertilisation inhibition occurs through direct toxicity effects of the copper.
• Copper can also have the effect of inhibiting sperm penetration of cervical mucus.
• Inflammatory reaction effects on the endometrium due to the copper IUCD being in situ can also prevent implantation.⁵
• The National Institute for Health and Clinical Excellence (NICE) advises that the most effective IUCDs should have at least 380 mm² of copper and have banded copper on the arms.

Timing of use

• Can be used up to five days after unprotected sexual intercourse (UPSI).
• If the timing of ovulation can be estimated, insertion can be beyond five days after UPSI, as long as insertion does not occur beyond five days of ovulation.⁵
• An IUCD should ideally be fitted at first presentation for emergency contraception (EC). It may be appropriate to delay the insertion in certain circumstances, e.g. until the next-day family planning clinic service is available. In such cases, progestogen-only emergency contraception (POEC) should be given in the interim.

Efficacy

• 99% of expected pregnancies are prevented.
• It is more effective as a form of EC than POEC.

Absolute contra-indications⁶

• History of copper allergy or Wilson's disease.
• Past attack of bacterial endocarditis in a woman with an anatomical lesion of the heart or after prosthetic valve replacement.
• Markedly distorted uterine cavity.

Risk of pelvic inflammatory disease (PID)

• There is a potential risk of PID when inserting an IUCD in a woman who has had UPSI.
• It is recommended that, as a minimum, women at higher risk of sexually transmitted infection (age ≤25 years, new sexual partner or ≥1 sexual partner in the previous year) should be offered testing for chlamydia.
• For such high-risk women, the use of prophylactic antibiotics should also be considered when the IUCD is inserted.

Other points

• Previous ectopic pregnancy is not a contra-indication to emergency IUCD use.
• Non-copper-containing IUCDs (including the Mirena® intrauterine system (IUS)) are not recommended for EC, as there is currently no available evidence of their effectiveness.
• The IUCD may be removed following the next menstrual period if not required as long-term contraception.
• It may also be removed if hormonal contraception is started within the first five days of the next cycle.

General points for women receiving emergency contraception

• Discuss information about the failure rate, and document this.
• Give a written advice sheet about emergency contraception (EC).
• Explain that their next period may be on time, early or late.
• Explain that they should return for a pregnancy test if they have not had a normal period within seven days of their expected next period or if they have irregular bleeding.
• Advise that they should see a doctor immediately if they develop lower abdominal pain (consider the possibility of ectopic pregnancy).
• Advise about a more definitive method of contraception for the future. Written information is helpful.
• Discuss the risk of sexually transmitted infection (STI). They have all had unprotected sexual intercourse. They should be referred for a full sexual health screen as appropriate.
• Examine and document Fraser-ruling competence if appropriate.¹⁴

Document references

1. Ulipristal Acetate (ellaOne®), New Product Review, Faculty of Sexual and Reproductive Healthcare (2009)
2. No authors listed; Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. Task Force on Postovulatory Methods of Fertility Regulation. Lancet. 1998 Aug 8;352(9126):428-33. [abstract]
3. Cheng L, Gulmezoglu AM, Oel CJ, et al; Interventions for emergency contraception. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD001324. [abstract]
4. Amy JJ, Tripathi V; Contraception for women: an evidence based overview. BMJ. 2009 Aug 7;339:b2895. doi: 10.1136/bmj.b2895.
5. Emergency Contraception, Faculty of Sexual and Reproductive Healthcare (2011)
6. John Guillebaud. Your Questions Answered: Contraception, 4th Edition
7. Emergency Contraception. Fact sheet No. 244, revised 2005, World Health Organization
8. Summary of Product Characteristics (SPC) - Levonelle® 1500 micrograms, Schering Health Care Limited, electronic Medicines Compendium, November 2009
9. Summary of Product Characteristics (SPC) - Levonelle® One Step, Schering Health Care Limited, electronic Medicines Compendium, March 2010
10. von Hertzen H, Piaggio G, Ding J, et al; Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial. Lancet. 2002 Dec 7;360(9348):1803-10. [abstract]
11. Summary of Product Characteristics (SPC) - ellaOne® 30 mg, HRA Pharma UK limited, Electronic Medicines Compendium. July 2010
12. Glasier AF, Cameron ST, Fine PM, et al; Ulipristal acetate versus levonorgestrel for emergency contraception: a Lancet. 2010 Jan 28. [abstract]
13. McKeage K, Croxtall JD; Ulipristal acetate: a review of its use in emergency contraception. Drugs. 2011 May 7;71(7):935-45. doi: 10.2165/11207410-000000000-00000. [abstract]
14. Contraceptive Choices for Young People, Faculty of Sexual and Reproductive Healthcare (2010)

Internet and further reading

• Contraception - emergency, Prodigy (March 2011)