Abstract:

Objective: To study and compare the secretion of pregnancy specific β1- glycoprotein (SP1) and human chorionic gonadotropin (hCG) by human pre- embryos, cultured in vitro, with their respective morphological development. Design: Spare human pre-embryos from randomly selected women participating in a program of in vitro fertilization (IVF) were studied prospectively. Setting: Pre-embryos were cultured, and hormone release was determined in academic research laboratories. Patients, Participants: Pre-embryos (n = 108) cultured for 14 days after fertilization in Ham's F-10 medium (GIBCO Ltd., Paisley, Scotland) were observed, and hCG and SP1 were measured in the culture media at regular intervals. Main Outcome Measures: Discordant secretion of SP1 and hCG. Results: Of the 98 bipronucleate pre-embryos, 53.6% formed blastocysts, 17.3% of which hatched. Human chorionic gonadotropin was detected from day 7 after fertilization concomitantly with blastocyst formation, thereafter showing a logarithmic increase (maximum 10,650 mIU) until the first signs of embryonic disintegration. Pregnancy- specific β1-glycoprotein release started 3 to 4 days after fertilization independently of the morphological development and the future production of hCG, thereafter displaying a nonlogarithmic increase (maximum 41 ng). Conclusions: Hormone secretion and morphological development are unique for each pre-embryo. Human chorionic gonadotropin and SP1 seem to have different biochemical and physiological regulation.