Serum levels of human placental lactogen and human chorionic gonadotropin in early pregnancy: a maturational index of the placenta.

Between weeks 10 and 20 of gestation, there are rapid and opposing changes in blood levels of two hormones produced by the syncytiotrophoblast; hPL increases and hCG decreases. In this study, the relationship between these two changing hormone levels was examined, rather than the serum concentrations themselves, as a potential test for placental maturation. The relationship between the hCG and hPL concentrations and GA determined in a selected group of patients was described by the following equation: GA (in days)=97.3 + 24.8 ln [hPL]-14.5 LN [HCG]. The endocrine evaluation of placental maturation by comparison of [hCG] and [hPL] in early pregnancy shows promise as a simple, safe, and inexpensive clinical tool for GA assessment.