Human chorionic gonadotropin increase in normal early pregnancy

Serial determinations of human chorionic gonadotropin have been used in evaluating early pregnancies. This has been based on linear regression of logarithm-transformed hCG levels. However, these levels are changing in a curvilinear fashion as pregnancy advances. Consequently the simple linear model does not provide a good fit to the data. To define more precisely the normal values for hCG increase, serial determinations were performed on serum …