PIP: This paper reviews the history of the Dalkon shield from its introduction in the late 1960s. The design of the Dalkon shield was based on the theory that an IUD with the greatest possible surface area would react with the endometrium in such a way as to inhibit conception. Studies in the early 70s established that there were more cases with complications, especially infections, among women who used IUDs with a thread extending down into the vagina compared with those who used IUDs without a thread. Later studies focused especially upon the multifilament thread used in the Dalkon shield. This thread, which consisted of 200-400 individual filaments within a thin nylon sheath, was found to have a wicking effect in which bacteria-contaminated fluids were transported from the vagina into the uterus. If a Dalkon shield remained in place during pregnancy, the normal expansion of the uterus drew the thread up through the cervix during the mid-trimester of pregnancy. This increased the rate at which bacteria could bypass the bactericidal environment of the endocervix and enter the cavity of the uterus. On the basis of these and other negative studies, the Dalkon shield was removed from the Norwegian market in 1974, although there are documented cases of Dalkon shields being inserted as late as 1980.