summary
Measurements were made of the coer remaining on used Gravigard intrauterine contraceptive devices (lUCDs) 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 coer loss decreased exponentially from 0–42 μmol d−1 (26–7 μg d−1) upon insertion to 0‐056 μimol d−1 (3–6 μg d−1) after 26 months of use; between 27 and 40 months of use a linear release of 0–32 μimol d−1 (20–3 μg d−1) was observed. There was no correlation between this changing rate of coer loss and the pregnancy rate with the device in situ. The changes in the rate of coer 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 coer; this results in a progressive increase in breakage of the coer wire after 3 years. It is recommended that a coer IUCD of this type be replaced after 3 years.
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