目的:评价不同用药时间小剂量米非司酮紧急避孕的临床效果、副反应及对月经的影响。方法:将380例年龄在18～45岁无避孕或避孕失效性交后5天内,要求采用补救措施的健康妇女分为两组:性交后72h(组Ⅰ)及性交后72～120h间(组Ⅱ),均口服米非司酮25mg,用门诊随诊形式,判断避孕效果、记录副反应及月经情况。按Dixon法推算避孕有效率。结果:两组实际妊娠数为1、2;失效率为0.6％、1.0％;避孕有效率为91.8％、80.4％,差异均无显著性(P>0.05)。服药后两组各种副反应均未超过10％且程度轻,组间无显著差异(P>0.05)。对月经影响:下次月经按期来潮两组分别为74％、70％,与平素月经量相似为83％、82％,经期如常者95％、92％。结论:性交后72h与72～120h间用25mg米非司酮紧急避孕均安全、有效。但随时间延长,失败率有增加的趋势。副反应及对月经影响与用药时间关系不 OBJECTIVE: To evaluate the clinical effects, side effects and the effect on menstruation of low dose mifepristone contraceptives in different periods of time. METHODS: One hundred and eighty healthy women aged 18-45 years without any contraceptive or contraceptive failure were asked to divide into two groups: 72 h after intercourse (group Ⅰ) and 72 ~ 120 h after intercourse (group Ⅱ ), Oral mifepristone 25mg, with out-patient follow-up form to determine the effect of contraception, recording side effects and menstrual conditions. According to Dixon method to calculate the effective contraception. Results: The actual number of pregnancy in both groups was 1, 2; the failure rates were 0.6% and 1.0%; the contraceptive efficiencies were 91.8% and 80.4% respectively, with no significant difference (P> 0.05). After taking the two groups of various side effects were not more than 10% and the degree of light, no significant difference between groups (P> 0.05). On the menstrual impact: the next menstrual cramps on schedule were 74%, 70%, and usually similar amount of menstrual flow was 83%, 82%, 95% normal menstruation, 92%. CONCLUSIONS: Emergency contraception with 25 mg of mifepristone is safe and effective between 72 h and 72 h after 120 h of intercourse. However, with the extension of time, the failure rate tends to increase. Side effects and menstrual effects and medication time is not