@ Dr Sarah J. Buckley 2024 www.sarahbuckley.com
First published in Australia’s Parents Pregnancy magazine, Autumn 1999, as “Your Hormones are your Helpers.” Updated to 2024
| Imagine this. Your cat is pregnant, due to give birth around the same time as you are. You have your bags packed for hospital and are awaiting the first signs of labour with excitement and a little nervousness. Meanwhile your cat has been hunting for an out-of-the way place — your socks drawer or laundry basket — where she in unlikely to be disturbed. When you notice, you open the wardrobe door, but she moves again. Intrigued, you notice that your observation, even your presence, seems to disturb the whole process. And, wish as you might to get a glimpse into the mysteries of birth before it is your turn, you wake up the next morning to find her washing her four newborn kittens in the linen cupboard. |
Why does birth seem so easy to our animal friends when it is so difficult for us? One obvious difference is the altered shape of the pelvis and birth outlet that is caused by our upright stance; our babies need to twist and turn to navigate these unique bends. Even our nearest cousins, the great apes, have a near-straight birth canal.
However, in every other way, human birth is like that of other mammals — those animals that suckle their young — and involves the same hormones: the body’s chemical messengers. These hormones, which originate in the deepest and oldest parts of our brain, contribute to the physical processes of labour and birth, as well as exerting a powerful influence on our emotions and behaviour.
If we can be more respectful of our mammalian roots, and the hormones that we share, we can have more chance of a straightforward birth ourselves.
Labour and birth involve peak levels of the mammalian hormone oxytocin, the hormone of love. Oxytocin also has critical roles in breastfeeding (lactation) and maternal-infant bonding in all mammals.
The stress hormones cortisol, adrenaline and noradrenaline (epinephrine and norepinephrine) are also involved in mammalian birth processes. There are many more hormonal influences on birth that are not well understood, including prolactin, melatonin and relaxin.
All mammals seek a safe place to give birth. This “nesting” instinct may be due to increase in levels of prolactin, which is sometimes referred to as the nesting hormone. At this stage, as you may have observed with your cat, interference which the nest — or more importantly with the feeling of safety — can stall the beginning of labour.
Even after labour has started, there are certain conditions that will slow, or even stop the process. If the fight-or-flight hormones are activated by feelings of fear or danger, contractions will slow down. Our mammalian bodies are designed to give birth in the wilds, where it is an advantage to postpone labour and to seek safety, if the labouring female senses danger.
For these reasons feeling private, safe and unobserved are basic needs for all labouring mammals, from mice to elephants and humans.
Similarly, many have had the experience of labour stopping when they enter the unfamiliar surroundings of a hospital, and some can be as sensitive as a cat to the presence of an observer. Giving birth away from our natural environment can cause the sorts of difficulties for humans that captive animals experience when giving birth in a zoo.
Natural birth pioneer Michel Odent, who writes about the need to ‘mamamlianise’ birth, cautions that even hunger, which also causes the body to release fight-or-flight hormones, can stop labour from progressing. He advises women to eat if they are hungry during labour. Many hospitals, though, have a policy that prevents labouring women from eating once they are admitted.
Oxytocin is the hormone that causes the uterus to contract during labour. Levels of oxytocin gradually increase as labour strengthens, triggered by the sensations of pressure in the cervix and vagina as the baby moves down. Oxytocin levels peak around the time of birth, promoting very effective contractions with the final pushing stage.
Oxytocin levels also increase in the brain over the course of labour, with calming and pain-relieving effects. By activating brain reward centres from labour to birth, oxytocin contributes to the euphoria and receptiveness that a mother can feel towards her baby after physiological (unmedicated) birth.
Oxytocin has important roles to play after the birth. Oxytocin causes vasodilation- opening of the blood vessels- on the new mothers chest that provides a natural and very effective warming mechanism for her skin-to-skin newborn. Skin-to-skin contact straight after birth allows the newborn to find the breast (also called the breast crawl) and will further increase oxytocin levels for both mother and baby. These oxytocin elevations will help them to recover from the stresses of labour and begin the oxytocin-related processes of breastfeeding and bonding.
Oxytocin also causes the contractions that lead to separation of the placenta from the uterus, and its release as the “after-birth”. High maternal oxytocin levels caused by maternal-newborn skin-to-skin contact following physiological birth will promote the strong contractions that reduce the chance of bleeding (postpartum haemorrhage.)
Oxytocin helps us in our emotional, as well as our physical, transition to motherhood. From the first weeks of pregnancy, oxytocin helps us to be more emotionally open and more receptive to social contact and support. Oxytocin stimulation of brain reward centres provides pleasure and reward for all mothering activities, especially infant contact and suckling/breastfeeding
Synthetic oxytocin is often given by drip – that is, directly into the bloodstream – when labour is too slow or contractions judged to be inefficient. Synthetic oxytocin given in this way does not enter the brain, and so does not have the direct calming and pain relieving effects of natural oxytocin in labour. While synthetic oxytocin does not reduce the labouring mothers own oxytocin production, increased pain and stress from stronger contractions may over-ride the oxytocin-linked calm and connection effects that help during physiological labour. In addition, high doses of synthetic oxytocin administered for a prolonged period in labour can reduce oxytocin sensitivity in the mothers uterus and increase the risks of postpartum haemorrhage.
The fight or flight hormones – also called catecholamines (pronounced cat-e-kol-a-meens), or CAs- are released with stress, which may interfere with oxytocin during labour and after the birth. However these hormones may have the opposite effect in the pushing (second) stage of labour, which is when birth actually occurs.
Early in second stage, when the cervix is fully open but the urge to push is not yet strong, a woman can feel the need to rest for some time. This is sometimes known as the “rest and be thankful” time. At some time after this, she may quite suddenly experience a dry mouth, dilated pupils and sudden burst of energy, and want to be upright at this time. These are all characteristic of high levels of CAs. The combination of high catecholamines and high oxytocin levels can promote very strong contractions, with an involuntary and irresistible urge to push. This has been called the ‘fetus ejection reflex’ and is the usual mechanism for birth in other mammals.
Some traditional cultures have used this fight-or-flight effect to help women who are having difficulty in birth by surprising or shouting out at this stage, causing a rush of catecholamines and a fast birth. Similarly, stress from entering the unfamiliar environment of the hospital in late labour can also trigger a catecholamine surge and a fast birth, even in the car park. It makes sense, at this point-of-no-return, for fear or danger to speed up the birth, so that a mother can then gather up her newborn baby and run for safety.
The baby also has very high levels of adrenaline and noradrenaline in labour, called the ‘fetal catecholamine surge,’
CA levels drop quickly after the birth, which can make a mother may feel cold or shaky. At this stage a very warm atmosphere may be essential to keep CA levels low and to allow oxytocin to work effectively to prevent bleeding.
Prolactin, another childbearing hormone, is most noteworthy for its effects after the birth. Prolactin is the major hormone of breast milk synthesis. Suckling by the newborn baby increases prolactin levels; early and frequent suckling from the first days makes the breast more responsive to prolactin, which in turn helps to ensure a good long-term supply of milk.
Beta endorphin (pronounced beet-a en-door-fin) is one of the endorphins that are released by the brain in times of stress or pain, and is a natural equivalent to painkilling drugs like pethidine.
During labour, beta-endorphin helps to relieve pain, and contributes to the “on another planet” feeling that women experience when they labour without drugs. Levels of beta-endorphin are reduced when drugs are used for pain relief.
Very high levels of beta-endorphin can slow labour by reducing oxytocin levels, which may help to “ration” the intensity of labour according to our ability to deal with it. Moderate levels of beta-endorphin help us to deal with pain in labour, as well as encouraging us to follow our instincts. As part of the hormonal cocktail after birth, beta-endorphin plays a role in bonding between mother and baby, who is also primed with endorphins from the birth process.
Beta-endorphin also switches on learning and memory, perhaps explaining why we remember our labour and birth in such amazing detail. Like oxytocin, endorphin hormones can induce euphoria and are also released during lovemaking and breastfeeding. In fact endorphins are actually present in breast milk, which explains the natural high that babies can get after a breast-feed. Beta-endorphin helps the body to release prolactin, underlining the elaborate interplay between these hormones of labour, birth and breastfeeding.
| So there you are, at the door, with your bag in your hand and a strong contraction. You remember the oxytocin and endorphins, which you also carry with you, and with your next relaxed breath, you breathe out fear and tension. You’ve packed your new nursing bra, and you know that prolactin will come to your aid as well. As you take a last look around the house, you notice your cat. She’s lying down as her kittens attach to her nipples, and as you catch her eye, she winks at you. |
