Early chorionic activity was assessed in the premenstrual days by means of serum HCG beta-fraction. As control, a group of women with no contraceptive use was studied; early chorionic activity was detected in 31.8% of the cycles. In the group bearing an inert IUD the incidence was 20%, which did not differ from the control; while in the medicated IUD groups (Cu-IUD and LNG-IUD) the incidences were 4.8% and nil, respectively. Both medicated IUD groups showed a significant difference when compared with the control, as well as the inert IUD groups. The meaning of these findings, pointing out differences in the main mechanism of action between inert and medicated IUDs, is discussed.
PIP: Early chorionic activity was compared in 100 IUD users (inert device, copper IUD, and a levonorgestrel-releasing IUD) and 22 controls through measurement of the serum human chorionic gonadotropin (hCG) beta-fraction. In the control group, 7 (32%) of the 22 women had hCG beta-fraction values indicative of chorionic activity (i.e., 5mIU/ml). In the group of women wearing an inert IUD (Lippes Loop), 8 (20%) were positive for early chorionic activity. In contrast, the incidence of premenstrual chorionic activity signs was very low among women with medicated IUDs: 5% among acceptors of the copper IUD and zero among women in the levonorgestrel-releasing IUD group. In general, elevated premenstrual hCG values are indicative of failed implantation. The high incidence of hCG activity recorded among Lippes Loop acceptors in this study is consistent with the anti-implantation effect postulated for inert devices. In contrast, medicated IUDs appear to act by preventing rather than interrupting implantation and therefore should not be regarded as abortifacient contraceptive agents.