Intrauterine contraceptive devices: failure of unilateral intrauterine device in inducing luteolysis in rabbits, rats and mice.

Insertion of a unilateral intrauterine device (IUD) on day 1 pc in rabbits and rats or day 2 pc in mice is found to interrupt pregnancy in the device-bearing uterine horn, but does not affect blastocyst implantation or fetal development of the contralateral side. It is also evident that following surgical ablation of the ovary of the non-IUD side, the ovary of the IUD-bearing side can effectively maintain pregnancy and fetal growth as in controls. The possible mode of action of the IUD has been discussed.