Human chorionic gonadotrophin (hCG) in IUD users.

 The incidence of postimplantation pregnancy loss was assessed in 186 IUD users and 187 controls through use of a highly sensitive, specific radioimmunoassay for serum human chorionic gonadotropin (hCG). Previous studies have detected hCG in 10-19% of IUD users during the postovulatory phase of the menstrual cycle, indicating either that implantation had occurred or that the preimplantation blastocyst secretes detectable amounts of hCG. 3 of the 187 controls had detectable serum hCG and their serum luteinizing hormone (LH) concentrations exceeded 125 mIU/ml. In 3 of 186 IUD users, serum hCG was detected in the presence of normal or low serum LH concentrations. These findings suggest that the incidence of dectable hCG during the postovulatory phase is extremely low in IUD users and identical to that of postmenopausal and noncycling controls. It is concluded that embryonic implantation and subsequent early abortion are rare events in IUD users and that neither plays a role in the mode of action of the IUD.
