Regulation of early gestational corpus luteum function in spontaneous and follicular stimulated conceptions.

Objective: To determine the regulatory role of hCG on P secretion in normal and abnormal (abortive and ectopic) first trimester pregnancies.

Study Design: The number of doublings of hCG per day (1/DT; reciprocal of hCG doubling time) was correlated with serum P using linear and nonlinear models in normal intrauterine pregnancies, spontaneous abortions, and ectopic pregnancies (EPs) conceived spontaneously or after clomiphene citrate (CC).

Results: Linear correlations between P and 1/DTs of hCG were poor. In contrast, nonlinear modeling with a hyperbolic curve fit the data well and allowed all of the data to be included for analysis regardless of the pregnancy type. Furthermore, this model could be used to explain the differential P concentrations seen in normal and abnormal first trimester pregnancies. The nonlinear hyperbolic model demonstrated that follicular events determine the maximal P production during early gestation. Human chorionic gonadotropin 1/DTs approximately equal to 0.5 sustain maximal P production. Progesterone production is then sustained by the rate of change of hCG.

Conclusion: Nonlinear correlation analysis suggests that P production in early gestations is regulated by prior follicular events and the rate of hCG production.