Factors that limit the efficiency of copper-carrying IUDs.

Contraceptive effectiveness and other major parameters of IUD use were measured clinically in women from Santiago Chile using the T T 30 T 120 T 200 T 340 7-200v 7-200h 7-250 and 7-300 devices. Studies with the T permitted a determination of the influence of increasing intrauterine copper surfaces upon pregnancy rates expulsion and side effects such as bleeding and pain. Studies with the 7 showed the influence on the same events of placing the copper wire near the area of implantation in the upper portion of the uterus. It was concluded that the copper surface placed on the devices is a determining factor in expulsion and pregnancy rates. The optimal surface area of copper needed to minimize expulsions is 120 sq. mm and to minimize pregnancy is 200 sq. mm. Any increase of this surface increases expulsions without significantly decreasing pregnancies. The copper should be located parallel to the vertical axis of the uterine cavity. If placed in the fundal region expulsions increase without diminishing pregnancies. Experience with the T 200 and 7-200v over a 3-year period shows a stationary pregnance rate; thus it appears that the contraceptive efficacy of the copper does not decrease. However rates of expulsion and bleeding do decrease in the 2nd and 3rd year.(AUTHORS MODIFIED)