Larsson B, Frankman O, Hamberger L
Fertil Steril. 1981 Dec;36(6):734-6. doi: 10.1016/s0015-0282(16)45917-0.
The useful life span of the two most commonly used copper intrauterine devices (Cu-IUDs) (Gravigard and Cu-T) was investigated in a long-term study up to 90 months after insertion. Minor differences between the two types of devices were found that, however, probably do not contribute to a diverging contraceptive efficacy with time. To be able to ensure maximal contraceptive effect, the authors suggest on the basis of the present data that the time of use not exceed 5 to 6 years.
在一项长达90个月的长期研究中，对两种最常用的含铜宫内节育器（Cu-IUDs）（Gravigard和Cu-T）的使用寿命进行了调查。发现这两种类型的节育器之间存在细微差异，然而，随着时间的推移，这些差异可能不会导致避孕效果出现差异。为了能够确保最大的避孕效果，作者根据目前的数据建议使用时间不要超过5至6年。
