Serum levels of hCG secretion throughout pregnancy measured by beta-subunit hCG radioimmunoassay

Serum human chorionic gonadotropin(hCG) was determined throughout pregnancy by β-subunit radioimmunoassay (RIA) which was highly specific to hCG but non-specific to human luteinizing hormone(hLH). Subjects were 112 normal pregnant women who had had the menstrual cycle of 27 to 30 days at least 4 cycles before pregnancy, and 2 healthy men. Measurements were made by labeling radioactive iodine to hCG β-subunit offered by NIAMD, and by usual double antibody method with hCG of NIAMD as standard. Serum hCG during the implantation period mostly reached to high level more than 20 days after the estimated ovulation day. During 6 to 40 weeks of pregnancy, serum hCG in most cases reached to remarkably high level of 4,500 ng/ml on 10th week and gradually decreased after 15th week varying between the level of 500 to 1,000 ng/ml. Most cases showed increase of serum hCG during 34 to 38 weeks of the late period of pregnancy, and maintained the level till delivery. Serum hCG during the childbed did not decrease rapidly, and was detected 120 hours after delivery in some cases indicating the long half life of hCG. (Mukohata, S.)