Ortiz M E, Croxatto H B, Bardin C W
Instituto Chileno de Medicina Reproductiva, Santiago, Chile.
Obstet Gynecol Surv. 1996 Dec;51(12 Suppl):S42-51. doi: 10.1097/00006254-199612000-00014.
The major effect of all intrauterine devices (IUD) is to induce a local inflammatory reaction in the endometrium whose cellular and humoral components are released into the uterine cavity. This inflammatory reaction has a variable effect on the reproductive strategy of the species studied. For example, this foreign body reaction can be localized within the uterus of rodents; and in farm animals it can have striking extrauterine effects. Thus, the action of IUDs in humans cannot be discerned from animals. In humans, copper ions released from Cu-IUDs enhance the inflammatory response and reach concentrations in the luminal fluids of the genital tract that are toxic for spermatozoa and embryos. In women using the IUD, the entire genital tract seems affected, at least in part, because of luminal transmission of the fluids that accumulates in the uterine lumen. This affects the function or viability of gametes, decreasing the rate of fertilization and lowering the chances of survival of any embryo that may be formed, even before it reaches the uterus. Studies on the recovery of eggs from women using IUDs and from women not using contraception show that embryos are formed in the tubes of IUD users at a much lower rate compared with nonusers. This is believed to be the major action of IUDs. Therefore, the common belief that the major mechanism of action of IUDs in women is through destruction of embryos in the uterus (i.e., abortion) is not supported by the available evidence. In Cu-IUD users, it is likely that few spermatozoa reach the distal segment of the fallopian tube, those that encounter an egg may be in poor condition. Thus, the few eggs that are fertilized have little chance for development and their possibility for survival in the altered tubal milieu become worse as they approach the uterine cavity.
所有宫内节育器（IUD）的主要作用是在子宫内膜诱导局部炎症反应，其细胞和体液成分会释放到子宫腔内。这种炎症反应对所研究物种的生殖策略有不同影响。例如，这种异物反应在啮齿动物子宫内可局限存在；而在农场动物中，它可产生显著的子宫外效应。因此，IUD在人类身上的作用无法从动物身上推断出来。在人类中，铜宫内节育器释放的铜离子会增强炎症反应，并在生殖道管腔液中达到对精子和胚胎有毒的浓度。使用IUD的女性，整个生殖道似乎至少部分受到影响，这是因为子宫腔内积聚的液体通过管腔传播所致。这会影响配子的功能或活力，降低受精率，并降低任何可能形成的胚胎的存活几率，甚至在其到达子宫之前。对使用IUD的女性和未采取避孕措施的女性回收卵子的研究表明，与未使用者相比，使用IUD的女性输卵管中形成胚胎的比率要低得多。这被认为是IUD的主要作用。因此，关于IUD在女性中主要作用机制是通过破坏子宫内胚胎（即流产）的普遍观点，现有证据并不支持。在使用铜宫内节育器的女性中，可能很少有精子到达输卵管远端，那些遇到卵子的精子可能状态不佳。因此，少数受精的卵子发育机会很小，而且随着它们接近子宫腔，在改变的输卵管环境中存活的可能性变得更差。
