The hormones epinephrine and norepinephrine (adrenaline and noradrenaline) are also known as the fight-orflight hormones, or, collectively, as catecholamines. They are secreted from the adrenal gland, above the kidney, in response to stresses such as fright, anxiety, hunger or cold, as well as excitement, when they activate the sympathetic nervous system for fight or flight.
High CA levels inhibit oxytocin production, therefore in the first stage of labour can inhibit or slow the labour. CA’s also act to reduce blood flow to the uterus and placenta, and therefore to the baby. This makes sense for animals who birth in the wild, where the presence of danger would activate this sympathetic response, inhibiting labour and diverting blood to the major muscle groups so that the mother can flee to safety.
In humans, high levels of CA’s have been associated with longer labours and adverse foetal heart rate patterns.(16) After an undisturbed labour, however, when the moment of birth is imminent, these hormones act in a different way. There is a sudden increase in CA levels, especially noradrenaline, which activates the foetal ejection reflex. The mother experiences a sudden rush of energy; she will be very alert, dry mouth and shallow breathing and perhaps the urge to grasp something. She may express fear, anger or excitement and the CA rush will cause several very strong contractions, which will birth the baby quickly and easily.
After the birth, CA levels drop steeply. The new mother may feel shaky or cold as a consequence. A warm atmosphere is important, as ongoing high CA levels will inhibit oxytocin and therefore increase the risk of postpartum haemorrhage.(17)
Noradrenaline, as part of the ecstatic cocktail, is also implicated in instinctive mothering behaviour.
For the baby also, birth is an exciting and stressful event, reflected in high CA levels.(18) These actually assist the baby during birth by protecting against the effects of hypoxia (lack of oxygen). High CA levels at birth ensure that the baby is wide-eyed and alert at first contact with his mother. The baby’s CA levels also drop rapidly after an undisturbed birth, being soothed by contact with the mother.