Contraceptive efficacy of two different metals using a modified seven vector.

Early studies with copper suggested that few improvements in overall IUD performance could be obtained with the use of more than 200 mm2 of copper. Thus, the use of other metals paired with copper has been investigated. This report of two studies of the small Copper-7, one with zinc and the other with copper alone, suggests that the addition of zinc in the superior position of the small Cu-7 decreases the incidence of pregnancy and that the small Cu-7 may be associated with higher retention rates than the standard Cu-7.