The pathway to human birth

Abstract

Preterm labour remains a major obstetric problem with only poor methods for prediction of preterm birth and treatments of preterm labour with limited efficacy. Regulation of human parturition is demonstrably different from that in most animals restricting opportunities for relevant research. Recent work suggests a placental clock mechanism regulating the length of pregnancy through the production of the placental peptide Corticotrophin Releasing Hormone. At the end of pregnancy most animals initiate labour with a fall in circulating progesterone concentrations but this does not happen in humans. In humans a functional progesterone withdrawal is initiated by a change in myometrial expression of progesterone receptors, specifically increase expression of the PRA isoforms, which is a dominant repressor of the activating receptor PRB. This new knowledge may help design better strategies for prediction and treatment of preterm labour.