The Trigger for Parturition in Sheep - Fetal Hypothalamus or Placenta

Abstract

The fetal pituitary-adrenal axis plays a pivotal role in the mechanisms leading to parturition in sheep. Fetal cortisol concentrations gradually increase in the last 15 days before term, with a marked increase occurring in the last 3-4 days. Some mechanism causes a marked increase in the stimulatory drive to the fetal pituitary resulting in increased secretion of ACTH from the pituitary, and subsequent cortisol secretion from the adrenal gland. In this paper we discuss the roles of the hypothalamus and placenta in triggering the onset of labour in sheep