The mechanism underlying the high contraceptive efficacy of the copper intrauterine device (IUD) is yet to be determined. Copper IUDs have numerous side effects leading to high and early removal rates. Preliminary work on the copper and an alternative (IUD) in our novel rat model indicates that both IUDs are an effective contraceptive, however, the uterus responds uniquely to the different metals contained in the IUD.
Histological studies identified local endometrial inflammation and metaplasia of the uterine epithelial cells (UECs) in response to copper. Energy dispersive x-ray spectroscopy detected accumulated copper ions in the underlying endometrium. The alternative IUD did not cause an inflammatory response or metaplasia of the UECs. An embryo survival assay was performed using embryos from IUD treated vs. non-treated control horns. This demonstrated that all ovulated oocytes were fertilised in both metal IUD horns, discounting the spermicidal effects of copper as the main mechanism of contraception. In the copper treated horn 15% of embryos collected at day 3 developed into blastocysts compared to 60% in the non-treated control horn. The alternative IUD yielded 6% of embryos developing into blastocyst compared to 67% in the control horn.
These findings suggest that copper ions contribute to the arrested development of embryos and in association with local inflammation and metaplasia of UECs, contributing to the high contraceptive efficacy of the copper IUD. The alternative IUD resulted in the lowest number of blastocysts and a lack of endometrial inflammation, indicating a decrease in side effects resulting in a novel non-hormonal long-term contraceptive for women.