The effect of intrauterine device (IUD) usage on the occurrence of fetal loss after the first trimester of pregnancy was investigated in the Women's Health Study, a multicenter case-control study of the relationship between IUD usage and the occurrence of serious gynecologic and obstetric disorders that was carried out in 16 US hospitals between 1976 and 1978. In this study, 539 cases of second-trimester fetal loss were compared with 336 matched controls. It was found that IUD use prior to conception did not increase the risk of second-trimester fetal loss. Also, if an IUD was in place at conception but was removed during the first trimester of pregnancy, the risk of second-trimester fetal loss was not increased. However, among women with an. IUD in place at conception that was not removed during the first trimester of pregnancy, the risk of second-trimester fetal loss was increased tenfold (relative to the risk among women not having an IUD in place at conception). This increase in risk was much greater for septic second-trimester fetal loss (relative risk approximately equal to 26, 95% confidence interval 6 to 108) than for nonsrptic fetal loss (relative risk approximately equal to 3, 95% confidence interval 0.3 to 22). From this study and from ancillary data concerning IUD usage and failure rates, it is estimated that about 600 cases of second-trimester fetal loss (septic and nonseptic combined) occur annually in the United States as a consequence of an IU of pregnancy. An IUD in place at the beginning of the second trimester of pregnancy also appears to increase the risk of third-trimester fetal loss, but the magnitude of this increase is uncertain.
(C) 1981 The American College of Obstetricians and Gynecologists