Shelton J D, Taylor R N
Am J Obstet Gynecol. 1981 Mar 1;139(5):592-6. doi: 10.1016/0002-9378(81)90522-6.
Data from 25 studies of intrauterine contraceptive devices show close agreement between the Pearl Pregnancy Index and a cumulative, 12 month, life-table pregnancy rate. Analysis of data from the early stages of these clinical trials shows the Pearl Index to be superior to the short-term life table in predicting the outcome of the study. The error introduced by using the Pearl Index as a single measure of contraceptive efficacy in clinical trials, under conditions in which those trials are often carried out, is probably very minor compared to the effect of situational factors that affect studies and to differences among various life-table methodologies. The real strength of the life-table analysis of contraceptive performance is not the single, summary, 12 month pregnancy rate it provides, but the complete picture of various reasons for termination over time, particularly when a large number of woman-months of experience has accrued.
25项宫内节育器研究的数据表明，Pearl妊娠指数与累积的12个月生命表妊娠率之间具有高度一致性。对这些临床试验早期阶段数据的分析表明，在预测研究结果方面，Pearl指数优于短期生命表。在通常进行临床试验的条件下，将Pearl指数用作临床试验中避孕效果的单一衡量指标所引入的误差，与影响研究的情境因素的作用以及各种生命表方法之间的差异相比，可能非常小。避孕效果生命表分析的真正优势不在于它所提供的单一的、概括性的12个月妊娠率，而在于随着时间推移终止妊娠的各种原因的全貌，尤其是当积累了大量的女性月经验时。
