Hormonal methods that have been used in Australia for emergency contraception include:
A Cochrane systematic review of trials which had included women seeking emergency contraception after a single episode of unprotected sexual intercourse (Cheng et al, 1999) compiled data comparing mifepristone (not available in Australia), levonorgestrel and the Yuzpe regime. It found:
Other reviews found:
From a review of eight studies of the Yuzpe regimen (Trussell, 1999), it is estimated that the regimen reduces the risk of pregnancy by 56 to 89 per cent. The preferred point estimate is that the Yuzpe regimen reduces the risk of pregnancy by 74 per cent.
A single multicentre study of women requesting emergency contraception after a single episode of unprotected intercourse (Taskforce on Postovulatory Methods of Fertility Regulation, 1998) found a crude pregnancy rate of 1.1 per cent in those given levonorgestrel and a crude pregnancy rate of 3.2 per cent in those given the Yuzpe regimen. It was estimated that levonorgestrel prevented 85 per cent of expected pregnancies and the Yuzpe regimen prevented 57 per cent of expected pregnancies. The efficacy of both treatments declined with increasing time since unprotected sexual intercourse. Nausea occurred in 23 per cent of those given levonorgestrel compared with 51 per cent of those given the Yuzpe regimen; vomiting occurred in six per cent of those given levonorgestrel compared with 19 per cent of those given the Yuzpe regimen. (If antiemetics are given, they should be taken 20- 30 minutes before the dose of contraceptive for maximum effect).
For both the Yuzpe and levonorgestrel regimens, pregnancy incidence rates have been found to increase from 0.5 per cent if given within 12 hours of unprotected intercourse to 4.1 per cent if given between 61 and 72 hours after unprotected intercourse (Piaggio et al, 1999).
A review of safety indicated no increased risk of venous thromboembolism associated with short-term use of postcoital contraceptive pills (Vasilakis et al, 1999). However, the safety of repeated use of emergency contraceptive regimes is not established. Women seeking emergency contraception should be counselled about other contraceptive options.
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