评价紧急避孕药效果的方法比较

Comparison of the method of using emergency contraception.

目的采用新Wilcox方法再评价紧急避孕药的效果,比较与Dixon方法的差异。方法华中科技大学同济医学院计划生育研究所以月经周期中每天相对月经第1天发生的妊娠概率估算法(新Wilcox方法),对2000年8月至2002年3月进行的两项紧急避孕临床研究(TrialⅠ小剂量米非司酮和左炔诺孕酮用于紧急避孕的随机对照研究;TrialⅡ左炔诺孕酮片诺爽用于紧急避孕的生物等效性研究)的避孕效果进行再分析。结果相对Dixon方法,采用新Wilcox方法来计算避孕有效率,TrialⅠ观察组从88.29%减少到83.29%,对照组从89.13%减少到83.57%;TrialⅡ对照组从72.66%减少到64.35%,观察组因无一例妊娠,故两种方法计算的避孕有效率相同。结论基于月经周期中每天相对排卵日计算妊娠概率的Dixon方法过高估计了紧急避孕药的效果。

Objective To re-estimate the efficacy of emergency contraceptive pills （ECPs） by new Wilcox method in contrast to Dixon method. Methods By employing data from two recent published clinical trials of emergency contraception （Trial Ⅰ from the randomized controlled studies on mifepriston with small doses and levonorgestrel for emergency contraception, and Trial Ⅱ from the relative bioavailability of levonorgestrel for emergency contraception）, we re - examined the effectiveness of the two ECPs regimen using new estimates of conception probabilities by cycle day relative to the first day of bleeding （new Wilcox method） at Family Planning Research Institute of Tongji Medical College, Huazhong University of Science and Technology from August 2000 to March 2002. Results In contrast to Dixon method, the effective rates in Trial i dropped from 88.29% to 83.29% in treatment group, and from 89. 13% to 83.57% in contrast controls,respectively, by the new Wilcox method. Similarly, the effective rates in Trial Ⅱ dropped from 72.66% to 64. 35% in contrast controls, and remained the same in treatment group for lacking of the occurrence of pregnancy. Conclusion Our results suggest that the Dixon method probably overstated the effectiveness of ECPs when based on conception probabilities by cycle day relative to day of ovulation.