Copper coil as emergency contraception
In the UK, the copper coil (a small T-shaped intrauterine device, or IUD, placed in the womb) ranks as the most effective form of emergency contraception, used after unprotected sex.
Remember
The copper coil is the most effective emergency contraception in the UK and can be fitted up to 5 days after unprotected sex. It contains no hormones, so a history of clots or migraine with aura does not limit it.
Three emergency options are available in the UK. Levonorgestrel (a progestogen, a hormone similar to progesterone) is a 1.5 mg tablet that works for up to 72 hours after unprotected sex and becomes less effective with each hour. Ulipristal acetate (a selective progesterone receptor modulator, a drug that partly blocks the progesterone receptor) is a 30 mg tablet that works for up to 120 hours, which is 5 days. The copper intrauterine device is the most effective option.
The coil can be fitted up to 5 days (120 hours) after unprotected sex, or up to 5 days after the earliest expected ovulation. Copper is toxic to sperm, so its main action is to prevent fertilisation (a sperm joining an egg). It does not rely on delaying ovulation, whereas both pills work mainly by delaying ovulation and so have little left to act on after ovulation.
The copper coil contains no hormones. Migraine with aura (warning symptoms, such as visual disturbance, that come before the headache) and a previous deep vein thrombosis (a blood clot, usually in a deep leg vein) are reasons to avoid oestrogen, so the combined pill, which contains oestrogen and progestogen, is not suitable. Neither condition limits the coil. Levonorgestrel and ulipristal contain no oestrogen, so they can be used when the combined pill cannot. An enzyme inducer such as carbamazepine (a medicine for epilepsy) speeds up liver enzymes and so lowers the blood levels of other drugs, which means the emergency tablets may be less reliable. The coil is not affected by other medicines.
Depending on the type, the coil can be left in for 5 or 10 years as regular contraception.
Key facts
- Time limits
- levonorgestrel works for up to 72 hours (3 days) and ulipristal for up to 120 hours (5 days), while the copper IUD can be fitted up to 120 hours (5 days) after unprotected sex or up to 5 days after the earliest expected ovulation.
- Ranking
- the copper IUD is the most effective of the three UK emergency methods, ahead of both emergency pills.
- How it works
- copper is toxic to sperm, so the main action is to prevent fertilisation, and the coil does not rely on delaying ovulation.
- Pregnancy rates
- in pooled studies the rate was about 0.1% with the copper IUD and about 1.5% with oral emergency contraception.
- Enzyme inducers
- carbamazepine and St John's wort may reduce oral emergency contraception, but the copper IUD is not affected by other medicines.
- Clots and migraine
- because the copper IUD contains no hormones, a history of clots or migraine with aura does not limit its use.
- Ongoing use
- depending on the type, the coil can be left in for 5 or 10 years as regular contraception.
Exam traps
- Ulipristal acetate works for up to 5 days (120 hours) after unprotected sex, which is longer than levonorgestrel, but it is still less effective than the copper coil.
- High doses of the combined pill (the old Yuzpe method) are not one of the three UK emergency methods, and in a large trial the older Yuzpe approach was less effective than levonorgestrel.
- The progestogen-only pill is a regular daily contraceptive and is not among the three UK emergency methods, so taking it after unprotected sex is not an accepted means of preventing pregnancy.
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