OP18.02: Effect of rising hCG levels on the human corpus luteum during early pregnancy

Abstract

BACKGROUND: During early pregnancy, the most important task of the corpus luteum (CL) is to produce sufficientprogesterone until the luteoplacental shift occurs. Progesterone production is closely related to the extensive vascula-ture surrounding and supplying the CL. The synthesis of both progesterone and factors controlling the vasculature inthe CL is regulated by hCG, which is released initially at rising levels from the placenta. The primary aim of thisresearch was to evaluate changes in the CL vasculature during early pregnancy. METHODS: Twenty naturally con-ceived pregnancies were examined weekly from weeks 5 to 11. At each visit, blood samples were obtained to determinethe concentrations of hCG, progesterone and 17-OH progesterone (17-OHP). The vasculature in the ovaries wasassessed using three-dimensional power Doppler ultrasonography. RESULTS: The vascular supply in the ovary con-taining the CL was greatest at week 5, and thereafter, declined continuously until week 11. The decrease in the vas-culature correlated with the decrease in 17-OHP. Mean hCG levels reached a maximum at week 8, progesterone levelsreached the nadir at week 7 and increased after that. CONCLUSIONS: Vasculature in the CL appears to be createdalready by the fifth week of pregnancy and it does not enlarge despite rising hCG levels. The activity of the CL duringpregnancy may be measured non-invasively by assessing its vasculature with three-dimensional ultrasonography.