The closest progesterone metabolites (4,5-dihydroprogesterones) are possible stimulants of the onset of labor

Abstract

The effects of 16α, 17α -cyclohexanodihydroprogesterone, the structural analogues of the closest progesterone metabolites (4,5-dihy-droprogesterones) on the uterine tissues of intact, impregnated, and pseudopregnant rats has demonstrated that they cause uterine epithelial destruction. This effect does not affect the rate and completeness of fetal implantation, but it may play a role during labor, by facilitating fetal rejection. Earlier studies have indicated that the above analogues of the metabolites of progesterone eliminate the latter-induced oxytocin receptor blockade and cause myometrial destruction in pseudopregnant animals. These facts suggest that by accumulating by the end of pregnancy, the natural progesterone metabolites (4.5-dihydroprogesterones) can act as trigger compounds - "labor hormones".