Maternal plasma beta-hCG in early human pregnancy.

Beta-human chorionic gonadotrophin (beta-hCG) was assayed twice weekly in plasma from 20 subjects from 4 to 16 weeks gestation; 14 of these were normal. There was an initial rise, a plateau at weeks 7 to 9, and a further rise to a maximum at week 11. Levels then dropped steadily to week 16. There was no significant difference when mean levels were subdivided and calculated according to the subsequent sex of the baby. Of the 6 abnormal subjects, the twin pregnancy initially showed normal levels but at week 11 to 13 these were at least one standard deviation above the mean. The plasma beta-hCG levels of the two subjects who aborted were more than one standard deviation below the mean at week 5. Three subjects treated with progestogen therapy had beta-hCG levels which fluctuated within normal limits. The trends of beta-hCG levels were similar to those of plasma hCG levels in the two subjects who had both assays performed but peak times were different. There was considerable within patient and also patient to patient variation in beta-hCG levels.