The role of cortisol in preparing the fetus for birth

Abstract

The glucocorticoids, cortisol and corticosterone, have a unique function in the fetus in inducing a wide range of enzymes before birth that have little or no function during fetal life but on which survival after birth is dependent. The loss of the placenta at birth deprives the fetus of a source of oxygen, glucose and heat (among many other things) for which alternatives must be available immediately if survival is to be assured. In anticipation of these needs several organs undergo maturational changes in late pregnancy aimed at meeting these requirements. The lungs mature structurally and functionally, becoming distensible and capable of coping with high surface tension when air enters the alveoli with the first breath. In the liver, glycogen accumulates and gluconeogenesis is initiated to meet the demands for glucose until feeding begins. There is an increase in the production of tri-iodothyronine and catecholamines in preparation for the sharp increase in metabolic rate and thermogenesis associated with breathing and the cold environment. All these dramatic maturational events are regulated by cortisol as are numerous others in most organ systems that contribute to neonatal well-being but on which survival is less dependent. Pharmacological manipulation of these systems before birth has made a substantial contribution to improving human health.

Litter-size-dependent intrauterine growth restriction in sheep

“…It is well established that the foetal HPA axis is activated during the pre-partum period and that the increase in circulating levels of cortisol in the foetus is important for both organ development and normal timing of parturition (Liggins, 1994). However, HPA-axis function appears to be suppressed in twin compared with single foetuses based on lower concentrations of ACTH and cortisol in the plasma and delayed onset of the pre-partum cortisol surge that determines time of parturition (Edwards and McMillen, 2002;Gardner et al, 2004).…”

Effects of repeated maternal betamethasone administration on growth and hypothalamic-pituitary-adrenal function of the ovine fetus at term

“…A late gestational increase in endogenous plasma cortisol occurs in fetuses of many species and is responsible for prenatal enzyme activation within target tissues, necessary for tissue and organ maturation (Liggins 1994). The regulation of fetal HPA function and adrenal cortisol output is multifactorial.…”

“…Various studies in animals have shown reductions in weight at birth ( Jobe et al 1998), alterations in organ ( Johnson et al 1981) and neuronal development (Uno et al 1990, 1994, Dunlop et al 1997, and increases in basal and stress-induced plasma cortisol concentrations postnatally (Uno et al 1994) after prenatal glucocorticoids. These last observations suggest that chronic fetal exposure to glucocorticoid may alter the development of the hypothalamo-pituitary-adrenal HPA axis in utero.…”

Effect of maternal nutrient restriction in early gestation on development of the hypothalamic-pituitary-adrenal axis in fetal sheep at 0.8-0.9 of gestation

“…In addition, the axis is central to various other processes including organ maturation (Liggins 1994), growth (Fowden 1995), and cardiovascular regulation (Tangalakis et al 1992). Thus, a functioning HPA axis is critical for normal development of the organism and any perturbations are likely to have consequences for a wide range of systems.…”