Mechanism of anti-implantation by copper IUD in the rabbit: Transport and recovery of Ova

The effect of copper and polyethylene IUDs on early gestation of the rabbit was studied. Although the copper IUD prevents implantation, the mechanism of action does not appear to involve a significant alteration of ovum transport through the oviduct. At time periods following ovulation when ova are normally found in the uterus, disappearance of ova and subsequent low recovery rates were noted in the uterine horn with copper IUD. Ova which could be recovered from the copper side exhibited morphological evidence of degeneration. It is postulated that the contragestational effect of the copper IUD in rabbits involves disappearance of the embryos and degeneration of any remaining ova.