Degradation of the copper-releasing intrauterine contraceptive device and its significance.

Measurements were made of the copper remaining on used Gravigard intrauterine contraceptive devices (IUCDs) that had been in utero for up to 40 months. The topography and composition of the surface deposits were analysed by scanning electron microscopy and energy-dispersive X-ray analysis. The rate of copper loss decreased exponentially from 0.42 mumol d-1 (26.7 micrograms d-1) upon insertion to 0.056 mumol d-1 (3.6 micrograms d-1) after 26 months of use; between 27 and 40 months of use a linear release of 0.32 mumol d-1 (20.3 micrograms d-1) was observed. There was no correlation between this changing rate of copper loss and the pregnancy rate with the device in situ. The changes in the rate of copper loss were probably due to the growth of a surface corrosion product which, due to internal stresses, fractured after about 2 years and exposed fresh copper; this results in a progressive increase in breakage of the copper wire after 3 years. It is recommended that a copper IUCD of this type be replaced after 3 years.