The cytology of the retained IUD with relation to the mechanism of action.

Cellular reactions to 82 IUDs retained for different periods of time have been examined using the "loopal smear" method. The smears were divided according to periods of retention and degree of inflammatory reaction. In 47 cases the inflammatory reaction was graded as moderate to severe, while in 35 cases the reaction was graded as mild. Since contraception was effective also in those cases presenting with mild reactions, it must be concluded that factors other than inflammation play a role in the contraceptive mechanism. Cells obtained from 15 IUD washings were incubated with Staphylococcus albus in order to identify macrophages. In none of these cases were macrophages identified, thus rendering questionable the hypothesis that the contraceptive effect of the IUD is based on phagocytosis of spermatozoa.