Uterine factors and risk of pregnancy in IUD users: a nested case-control study

Scarce data are available on the relation between the effectiveness of intrauterine device (IUD) and the gynecologic features of a woman. A nested case-control study was conducted to determine whether the uterine position and hysterometry affect the pregnancy rate of copper IUD. Seventy-one cases (pregnant women with IUD) and 284 matched controls (1:4) were included. Matching criteria were date of IUD insertion and duration of use. Data were analyzed by conditional logistic regression modeling that considered age, parity and copper surface of IUD as potential confounders. When cases were compared to nonpregnant controls with IUD, the results showed that uterine position and hysterometry were not associated with an increased risk of pregnancy. The findings suggest that the gynecological characteristics of the woman analyzed should not be a criterion for the selection of potential IUD users. [Copyright &y& Elsevier]