Evidence for maternal regulation of progesterone production at midpregnancy in the mouse

Mice with major differences in embryo survival and progesterone secretion were used to study the relative roles of maternal and embryonic genotype in the control of progesterone production at midpregnancy. Reciprocal transfer of embryos from strains with high (Line S1) or low (Line G) embryo survival resulted in progesterone concentrations consistent with maternal genotype in females carrying the same number of fetuses. This suggests that maternal rather than fetal gene expression determines the setpoint for progesterone production during the period of transition from maternal to fetal-placental control of ovarian steroidogenesis.