Sivin I, Schmidt F
Population Council, New York, New York 10021.
Contraception. 1987 Jul;36(1):55-84. doi: 10.1016/0010-7824(87)90061-8.
Large, multicenter, randomized trials of IUDs conducted between 1970 and 1986 encompass more than 50,000 woman-years of experience in the two-year interval following device insertion. Taken singly and collectively, these trials demonstrate that IUD failure rates are strongly affected by the age of participants, notably by the proportion of women under age 25 admitted to the studies. Individual trials and overall comparisons indicate further that: 1. Non-medicated devices such as the Mahua steel ring and Lippes loop D have pregnancy rates above 2 per 100 woman-years. 2. The first approved copper IUDs, the Copper 7 and the TCu 200, do not markedly differ in pregnancy rates from standard plastic devices with rates significantly above 2 per 100 woman-years. 3. Five more recent, widely used copper IUDs have had failure rates significantly below 2 per 100 woman-years in multicenter trials. The point estimate of the failure rate was less than 1 pregnancy per 100 woman-years for three of these IUDs. One copper-bearing device had a failure rate significantly below 1 per 100 woman-years. 4. Devices releasing either 25 mcg/day of progesterone or 2 mcg/day of levonorgestrel have had significantly higher failure rates than the more effective copper-releasing IUDs; however, devices releasing 20 mcg/day of levonorgestrel appear at least as effective as the most effective copper IUDs. Long-term IUD failure rates derived from straight assignment as well as randomized trials indicate 4-year gross cumulative failure rates do not exceed 10 per 100 for any of the standard copper devices or the Lippes loop D. Point estimates of the four-year gross cumulative pregnancy rates have been below 5 per 100 users in studies of the TCu 220C, the Nova T, the TCu 380A, and the MLCu 375.
1970年至1986年间开展的关于宫内节育器（IUD）的大型多中心随机试验，涵盖了超过50000妇女年的随访经验，随访期为放置宫内节育器后的两年。单独来看或总体来看，这些试验都表明，IUD的失败率受参与者年龄的强烈影响，特别是纳入研究的25岁以下女性的比例。个别试验和总体比较进一步表明：1. 非药物型宫内节育器，如麻花铜环和Lippes D形环，每100妇女年的妊娠率高于2%。2. 最初获批的含铜宫内节育器，即铜7和TCu 200，其妊娠率与标准塑料宫内节育器相比无显著差异，均显著高于每100妇女年2%。3. 近期广泛使用的另外五种含铜宫内节育器，在多中心试验中的失败率显著低于每100妇女年2%。其中三种宫内节育器失败率的点估计值低于每100妇女年1次妊娠。一种含铜宫内节育器的失败率显著低于每100妇女年1%。4. 每天释放25微克孕酮或2微克左炔诺孕酮的宫内节育器，其失败率显著高于更有效的含铜宫内节育器；然而，每天释放20微克左炔诺孕酮的宫内节育器似乎至少与最有效的含铜宫内节育器一样有效。从直接分配以及随机试验得出的宫内节育器长期失败率表明，对于任何标准含铜宫内节育器或Lippes D形环，4年的总累积失败率不超过每100人10%。在对TCu 220C、Nova T、TCu 380A和MLCu 375的研究中，4年总累积妊娠率的点估计值低于每100使用者5%。
