Biological variation of free β chorionic gonadotropin and pregnancy-associated plasma protein A in first trimester pregnancies

Abstract

We found high biological variation for plasma concentrations of hCGβ and PAPP-A, increasing with longer time intervals between sampling. From our data that showed high correlation of hCGβ and PAPP-A in the first and second sample, we found no reason to recommend retesting. However, new studies should clarify whether PAPP-A should be collected early, and hCGβ late, in the first trimester of pregnancy.