Pregnancy rates during long-term use of copper IUDs.

990 cases of women using standard copper IUDs (Cu 7; Cu T; Multiload) up to a maximum period of 8 years have been analyzed statistically. The long-term use effectiveness was evaluated mainly by using statistical methods (life table). Pregnancy rates decreased during the whole period of observation but more evidently after 2 years of use. It is recommended that medicated IUDs, free of side effects, be exchanged only after 5 years of use, corrosive changes being not too far advanced after this period. New IUD models are less likely to be subject to corrosion and will therefore need to be replaced less frequently.