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Objectives: Most modem IUDs contain more than 300mm^sup 2^ of exposed copper to increase efficacy. We undertook a systematic review of randomised trials that had differing copper loads but identical plastic frames to assess the effects of increasing the copper load.
Design and methods: Medline and the Cochrane Library (2004) were searched for all randomised trials of IUDs, the abstract were reviewed and possible articles retrieved. Trials were included that compared IUOs with identical frames but cooper loads that differ more than 1OO mm^sup 2^ in copper surface area. Trial quality was assessed to see if effects varied with quality. Ratios of cumulative rates, or ratios of Pearl rates when cumulative...