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Interventions for emergency contraception

  • Review
  • Intervention




Emergency 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.


To determine which emergency contraceptive method following unprotected intercourse is the most effective, safe and convenient to prevent pregnancy.

Search methods

The 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 criteria

Randomised 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 analysis

Data 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 results

Eighty-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 conficence 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' conclusions

Mifepristone 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.




在未做保護措施的性行為後,使用藥物或避孕器可以達到緊急避孕的目的. 除了一些西歐國家及中國, 緊急避孕方法在世界各國並未被廣泛熟知及運用. 在許多開發中國家, 由於緊急避孕並不普遍, 許多婦女不得不在懷孕後實行人工流產, 以至於伴隨不安全流產之併發症及死亡率提高. 目前, 一些方法如子宮內避孕器, Yuzpe 治療, levonogestrel, mifepristone, danazol及一些合併療法可用於緊急避孕. 了解這些避孕方法在效果, 安全及便利性上孰優孰劣, 對於生殖科醫師及有緊急避孕需要的女性, 是相當重要的.


確定在未做保護之性行為後,何種為最有效, 安全及便利的緊急避孕方法.


搜尋 Cochrane Controlled Trials Register, Popline, MEDLINE, 中文生物醫學資料庫和UNDP/UNFPA/WHO/World Bank Special Programme on Human Reproduction (HRP)緊急避孕資料庫(July 2003).聯繫專家和藥廠.






納入48試驗共33110 女性.大部分試驗都在中國(37/48). Levonorgestrel 比Yuzpe療程能更有效避孕(2 試驗, RR: 0.51; 95% CI: 0.31−0.83). levonorgestrel使用單一劑量(1.5 毫克) 與隔12小時各服一半劑量(兩次各0.75 毫克) 效果相當. (2 試驗, RR: 0.77, 95% CI: 0.45 −1.30). Levonorgestrel 與mifepristone中劑量 (8 試驗, RR: 1.64; 95% CI: 0.82−3.25)或mifepristone低劑量 (7 試驗, RR: 1.38; 95% CI: 0.93−2.05) 效果相當.若只分析品質優良的試驗,結果顯示低劑量 (= < 10 毫克) mifepristone 療效與中劑量(25−50毫克)相當. 下次月經延遲是mifepristone 的主要不良作用,似乎和劑量有關. 沒有levonorgestrel 和 mifepristone時可用Yuzpe 療程.半劑量Yuzpe 單次服用與較少副作用相關,但不知其療效使否與標準Yuzpe 療程相當(RR: 1.41; 95% CI: 0.76 to 2.61).


Levonorgestrel 1.5毫克(固定劑量分為兩次服用或單次服用)和mifepristone低中劑量(25−50毫克)效果好且副作用可接受.單一劑量levonorgestrel較方便副作用也不會增加,但mifepristone,尤其高劑量,可能延遲下次月經週期,會增加焦慮. 沒有levonorgestrel 和 mifepristone時可用Yuzpe 療程.子宮內避孕器是另一種緊急避孕的有效方法,可持續避孕功效.



此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。


緊急避孕是未避孕性行為後為了預防懷孕而使用藥物或子宮內避孕器.這只是備用性質,非常規避避孕方式. Levonorgestrel 和 mifepristone 很有效,副作用少,比雌激素和黃體素併用好. 可服用Levonorgestrel以單一劑量(1.5毫克),不需間隔12小時分兩次服用(各0.75 毫克). Mifepristone可能延遲下次月經週期,需告知病患,讓其免於焦慮.子宮內避孕器是另一種有效的緊急避孕方法,可提供持續性的避孕功效.

Plain language summary

Methods of Emergency Contraception

Emergency contraception is using a drug or copper intrauterine device (Cu-IUD) to prevent pregnancy after unprotected sex. This is for backup, not regular contraception. Mifepristone and levonorgestrel are very effective with few adverse effects, and are preferred to oestrogen and progestogen combined. Levonorgestrel could be used in a single dose (1.5 mg) instead of two split doses (0.75 mg) 12 hours apart. Another effective method for emergency contraception is Cu-IUD and it can be kept for ongoing contraception.