• L Cheng, A M Gülmezoglu, G Piaggio, E Ezcurra, and P F A Van Look.
• China Welfare Institute, International Peace Maternity and Child Health Hospital (IPMCH), 145 Guangyuan Road, 910 Hengshan Road, Shanghai, China, 200030. linanc@online.sh.cn
• Cochrane Db Syst Rev. 2008 Apr 16 (2): CD001324.

BackgroundEmergency contraception is using a drug or copper intrauterine device (Cu-IUD) to prevent pregnancy shortly after unprotected intercourse. Several interventions are available for emergency contraception. Information on the comparative efficacy, safety and convenience of these methods is crucial for reproductive health care providers and the women they serve.ObjectivesTo determine which emergency contraceptive method following unprotected intercourse is the most effective, safe and convenient to prevent pregnancy.Search StrategyThe search included the Cochrane Controlled Trials Register, Popline, MEDLINE, PubMed, Biosis/Embase, Chinese biomedical databases and UNDP/UNFPA/WHO/World Bank Special Programme on Human Reproduction (HRP) emergency contraception database (December 2006). Content experts and pharmaceutical companies were contacted.Selection CriteriaRandomised controlled trials and controlled clinical trials including women attending services for emergency contraception following a single act of unprotected intercourse were eligible.Data Collection And AnalysisData on outcomes and trial characteristics were extracted in duplicate and independently by two reviewers. Quality assessment was also done by two reviewers independently. Meta-analysis results are expressed as relative risk (RR) using a fixed-effects model with 95% confidence interval (CI). In the presence of statistically significant heterogeneity a random-effect model was applied.Main ResultsEighty-one trials with 45,842 women were included. Most trials were conducted in China (70/81). There were more pregnancies with levonorgestrel compared to mid-dose (25-50 mg) (15 trials, RR: 2.01; 95% CI: 1.27 to 3.17) or low-dose mifepristone (<25 mg) (9 trials, RR: 1.43; 95% CI: 1.02 to 2.01). Low-dose mifepristone was less effective than mid-dose (20 trials, RR:0.67; 95% CI: 0.49 to 0.92), but this effect was no longer statistically significant when only high quality trials were considered (6 trials, RR: 0.75; 95% CI: 0.50 to 1.10). Single dose levonorgestrel (1.5 mg) administration seemed to have similar effectiveness as the standard 12 hours apart split-dose (0.75 mg twice) (2 trials, 3830 women; RR: 0.77, 95% CI: 0.45 to 1.30). Levonorgestrel was more effective than the Yuzpe regimen in preventing pregnancy (2 trials, RR: 0.51; 95% CI: 0.31 to 0.83). CDB-2914 (a second-generation progesterone receptor modulator) may be as effective as levonorgestrel (1 trial, 1549 women; RR:1.89; 95% CI: 0.75 to 4.64) but the confidence interval is wide and the result compatible with higher or lower effectiveness. Delay in the onset of subsequent menses was the main unwanted effect of mifepristone and seemed to be dose-related.Authors' ConclusionsMifepristone middle dose (25-50 mg) was superior to other hormonal regimens. Mifepristone low dose (<25 mg) could be more effective than levonorgestrel 0.75 mg (two doses) but this was not conclusive. Levonorgestrel proved more effective than the Yuzpe regimen. The copper IUD was another effective emergency contraceptive that can provide ongoing contraception.

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