title: Appearance of hCG in pregnancy plasma following the initiation of implantation of the blastocyst.
abstract: Plasma chorionic gonadotropin levels were measured by three different assay methods during early pregnancy in four patients following induction of ovulation with Pergonal and hCG. Radioligand-receptor assay of unextracted samples was subject to non-specific interference by plasma proteins, causing an apparent elevation of gonadotropin levels during the first few days after fertilization. By contrast, the gonadotropin values measured by a highly sensitive LH/hCG bioassay were consistent with those obtained with a sensitive and specific radioimmunoassay for hCG, and showed that the first significant rise in plasma hCG occurred 9 to 13 days after ovulation. These results indicate that hCG does not appear in the maternal circulation until after the initiation of implantation of the blastocyst.
mesh_terms: D001681:Biological Assay; D001798:Blood Proteins; D006063:Chorionic Gonadotropin / Q000097:blood*; D010064:Embryo Implantation; D005260:Female; D006801:Humans; D010060:Ovulation; D011869:Radioligand Assay
chemical_list: D001798:Blood Proteins; D006063:Chorionic Gonadotropin