The Hormones of Labour & Birth
A different way to think about birth
Have you ever wondered why our pets seek out a quiet, dark, and private space to give birth? You might have noticed that your furry friend has chosen to burrow into your favourite dressing gown, prompting you to disturb them to save your cuddly, warm, and well-worn dressing gown from being covered in birthing remnants. Now that you’ve interrupted her, she scurries away. This makes you pause and compare your own birthing wishes with your fur child’s labour and birth process.
Why does birth seem easier for animals?
Why do our pets seem to birth so easily, yet the process seems so difficult for us?
Human babies are born the same way as all mammals, using the same hormones — the body’s chemical messengers. These hormones, which stem from the deepest and oldest parts of our brain, assist the physical processes of labour and birth and influence our behaviours and emotions.
If humans respected their origins as mammals more, the hormones they share at birth could be much more like those of other animals.
Oxytocin: the hormone of birth
For labour and birth to function, the hormone oxytocin must be present. Oxytocin is responsible for love and bonding, and it also plays a critical role in breastfeeding for all mammals.
It is needed in labour and birth for the uterus to contract and for boosting the production of prostaglandins, which help stimulate uterine contractions. As oxytocin levels rise, so does the strength of labour, triggered by pressure on the cervix as the baby moves down.
Oxytocin also acts as a natural pain relief by activating the brain’s reward centres during labour and birth, often experienced as a sense of euphoria during a physiological birth.
When labour is progressing as expected, oxytocin levels — alongside prostaglandins — are sufficient to maintain consistent and strong contractions.
If your labour stalls or does not begin on its own, you may be offered the synthetic hormone Syntocinon to assist your uterus in contracting. It is important to note that Syntocinon is administered into a vein, not your brain, where natural oxytocin is released. This means the same love, bonding, and pain-relieving effects seen with natural oxytocin are not present with artificial oxytocin.
In fact, high doses of synthetic oxytocin over a prolonged period can reduce natural oxytocin sensitivity and increase the risk of postpartum haemorrhage.
The role of stress hormones
For labour and birth to work, we also need a mixture of stress hormones known as catecholamines.
Adrenaline and noradrenaline — commonly referred to as our “fight or flight” hormones — are triggered by feelings of stress or excitement. When adrenaline is released, the body undergoes physical changes such as a faster heart rate and more efficient lung function. Blood is redirected to the brain, arms, and legs, preparing the body to act if needed.
Adrenaline is very important during birth, as it helps promote a sense of safety and alertness. It is continuously dispersed throughout labour and provides the energy needed to birth your baby.
However, like animals, our bodies will also use these hormones to pause labour if danger is sensed.
The fetal ejection reflex
When a woman is in the early part of the second stage of labour — when the cervix is fully dilated but there is not yet an urge to push — she may feel a desire to rest.
Suddenly, she may experience a burst of energy from high catecholamine levels. Combined with oxytocin, these hormones can promote strong contractions, leading to involuntary pushing, often referred to as the fetal ejection reflex.
These hormone levels drop quickly after birth, which can leave the mother feeling shaky or cold.
Prolactin and breastfeeding
Another essential hormone for labour and birth is prolactin, which plays a key role after birth in breast milk production.
When the newborn begins suckling at the breast, prolactin levels increase. Early and frequent suckling helps the breast become more responsive to prolactin, supporting a sufficient long-term milk supply.
Beta-endorphins: the natural pain relief
Our final key hormone is beta-endorphins.
Released by the brain during times of stress or pain, beta-endorphins can be as effective as pain-relieving drugs like pethidine. They help mothers enter a deeply focused, altered state often referred to as “labour land.”
However, the use of pharmacological pain relief during labour can reduce the levels of this hormone.
Beta-endorphins also play a role in memory and learning, which may explain the vivid recollections many women have of their birth experience. Like oxytocin, they contribute to feelings of euphoria and are also released during breastfeeding.
Interestingly, endorphins are present in breastmilk, contributing to the calm, content feeling babies often experience after feeding.
What happens when we feel unsafe
Now, returning to your labouring cat: when you disturb your furry friend, it can trigger feelings of fear, unsafety, and heightened alertness. This leads to an overproduction of adrenaline and inhibits the release of oxytocin — ultimately stalling or even stopping labour.
In humans, this is often seen during the transfer from home to hospital in early labour. Contractions that were regular and intensifying at home may slow down or become more manageable due to peaks in adrenaline and noradrenaline, which suppress oxytocin.
By disrupting the safe space your cat chose, you undermine their sense of safety — and the same can happen in human birth.
The importance of environment
All of these hormones must work together to support a mammalian labour and birth process. While we understand many of these mechanisms, there are still factors influencing birth that we are continuing to learn about.
Evidence shows that all mammals — whether human or animal — seek a safe place to give birth. This behaviour is known as the nesting instinct.
To labour effectively, we must feel:
Safe
Calm
Private
Final thoughts
When we support these fundamental needs, we support the natural hormonal flow of labour — and ultimately, the birth experience itself.