IUDs are contraceptives, not abortifacients: a comment on research and belief.

No studies show that IUDs destroy developing embryos at rates higher than those found in women who are not using contraceptives. Studies of early pregnancy factors have not shown statistically significant differences in transient levels of hCG between IUD and control groups, a sign of early abortion. The small, careful study by Segal et al. (1985) found no transient rise of hCG in the IUD group. The highly sensitive assay in a larger sample of IUD users, by Wilcox et al. (1985), suggests that an upper limit of only 3 or 4 percent of ovulatory matings with an IUD in situ might show transient rises of hCG. The electron microscopy of Hurst et al. (1980) demonstrated the existence of leukocyte-ridden degenerating embryos in rhesus monkeys fitted with IUDs, but found the same percentage of degenerating embryos in the control group. In this respect, IUDs do no more than nature. The work of Hurst et al. also demonstrates the comparative rarity of fertilized ova in rhesus monkeys fitted with IUDs. Croxatto (1974) and Alvarez et al. (1988) showed that this was also true for humans. A variety of studies demonstrate that IUD use diminishes both the number of sperm reaching the oviduct and their capacity to fertilize ova. Depending on the type of IUD and the drug dose, sperm are hindered from penetrating cervical mucus, are phagocytized by leukocytes, are incapacitated, with head-tail separation in the presence of copper, and suffer other cytotoxic effects in the IUD-altered uterine fluid. In the oviducts of copper-IUD users, ova are found significantly less frequently than in controls.(ABSTRACT TRUNCATED AT 250 WORDS)