A possible role for progesterone metabolites in human parturition.

There has been a recent resurgence of interest in the role of progesterone in the maintenance of human pregnancy and the onset of labour, following recent reports of its use to prevent preterm labour in high-risk patients. One possible mechanism by which progesterone might contribute to uterine quiescence is through the actions of its metabolites. This article provides a brief overview of progesterone in human pregnancy and an outline of progesterone metabolism in the various reproductive tract tissues as well as the evidence for actions of progesterone metabolites in pregnancy.