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History

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Image not available. A 17-year-old woman requests emergency contraception on a Monday morning. She has been sexually active with her new partner for the past few weeks and had unprotected sexual intercourse (UPSI) two days ago. Her last menstrual period was three weeks ago.

What are the two main methods of emergency contraception?

What is their mode of action?

Which factors would help you to decide which method to use?

What additional questions would you like to ask?

What are the important aspects of follow-up?

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Background

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What are the two main methods of emergency contraception?

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Image not available. The purpose of emergency contraception is to provide women with a safe means of preventing pregnancy following either unprotected sexual intercourse (UPSI) or potential contraceptive failure.1

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The two main methods currently available are the progesterone pill, containing 1.5 mg levonorgestrel (LNG), which is given as a single dose, and the copper-containing intrauterine contraceptive device (IUCD). The most commonly used method is the LNG-containing pill and this is licensed to be given within 72 hours of unprotected intercourse, although it is known to have some efficacy for up to 120 hours after UPSI.2 The sooner the pill is administered, the greater the efficacy. Despite the fact that the LNG-containing pill is now readily available in pharmacies in countries such as the United Kingdom (UK), its use amongst women requesting termination of pregnancy (TOP) remains low (1% in 1984, 6% in 1996 and 12% in 2002).3 The IUCD is the more effective of the two methods. Insertion of a copper IUCD is effective up to 120 hours (five days) after intercourse, or up to five days after the earliest possible date of ovulation (ovulation occurs 14 days prior to menstruation). The LNG-containing intrauterine device is not recommended.

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What is their mode of action?

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The mode of action of oral LNG is incompletely understood but appears to relate to prevention of ovulation, rather than inhibition of implantation.1 The mechanism of action of the IUCD is clearer and relates to the direct toxicity of the copper contained within the device. This produces pre- and post-fertilization effects.4 It may be inserted up to five days after the most likely date of ovulation and, if given at this time, will produce an inflammatory reaction within the endometrium, preventing implantation.5 If given earlier in the cycle, its principal action is to prevent fertilization, and alterations in the copper content of the cervical mucus probably also inhibit sperm penetration.5

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Which factors would help you to decide which method to use?

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The date of the last menstrual period and whether it was in any way abnormal are crucial in determining which method of emergency contraception to offer (Figure 29.1) Not only does this allow you to assess the risk of pregnancy but ...

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