15.2 Emergency contraception
Introduction
Emergency contraception (EC) or post-coital contraception can be defined as preventing pregnancy after sexual intercourse. Every year over 3.5 million unintended pregnancies occur in the United States alone, mostly to teenage mothers. It is believed that half of these unintended pregnancies could be avoided by the judicious use of EC. Indications for the provision of EC are shown in Table 15.2.1.1
Many of these unintended pregnancies are later surgically terminated. Estimates of as many as 170 000 such terminations are performed in England and Wales annually.2 These surgical terminations are not without clinical risk and cost, as well as being a major social, religious and political issue.
Available medications
Historically, the Yuzpe method of EC was commonly practised in Australasia. This involved a high-dose oestrogen/progestogen preparation. Two doses of 100 mcg of ethinylestradiol combined with 500 mcg of levonorgestrel given 12 hours apart resulted in withdrawal bleeding within 21 days for 98% of women.3
While the precise mechanism by which LNE prevents pregnancy is not clear, it is believed to work by preventing ovulation and by altering the tubal transport of sperm and ova. Fertilisation is thus prevented. When used within 72 hours of unprotected sexual intercourse, LNE EC prevents 85% of expected pregnancies. Efficacy falls with time (Table 15.2.2).
| Hours post-coital | Pregnancies prevented (%) |
|---|---|
| <24 | 95 |
| 24–48 | 85 |
| 49–72 | 58 |
LNE contraception has fewer side effects than the traditional Yuzpe method. Only 20% of patients experience nausea, which usually responds to standard anti-emetics. LNE EC results in 60% of women commencing their next menstruation within 3 days of their expected date. Fifteen percent of women can be up to 7 days late with their period. It is essential that women have pregnancy testing if their period is more than 7 days late.6
If inserted up to 5 days after predicted ovulation, IUCDs can prevent 99% of expected pregnancies.5 Relative contraindications are nulliparity and patients who are at high risk of sexually transmitted infection.
