Sarah Buckley MD
First published in Australia’s Parents’ Pregnancy magazine Autumn 1999 as ‘Your Hormones are Your Helpers’
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 4 newborn kittens in the linen cupboard.
Birth among mammals
Why does birth seem so easy and matter-of-fact to our animal friends when it is so difficult for us? There are certainly anatomical differences, such as the altered shape of the pelvis and birth outlet that is a result of our upright stance. Our babies need to twist and turn to navigate these convolutions, whereas even our nearest cousins, the great apes, have a near-straight birth canal.
However, all other features of human birth are shared with other mammals- those animals that suckle their young. The birth process involves the same hormones- the body’s chemical messangers- in all species of mammal. These hormones, which originate in the deepest and oldest parts of our brain, cause the physical processes of labour and birth, as well as exerting a powerful influence on our emotions and behaviour.
Researchers such as French surgeon and natural birth pioneer Michel Odent believe that 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.
The hormones of birth
Labour and birth involve peak levels of the hormones oxytocin- sometimes called the hormone of love- and prolactin, the mothering hormone. These two hormones are perhaps best known for their role in breastfeeding. As well as these, beta-endorphin, the body’s natural pain-killer, and the flight-or-fight hormones adrenaline and noradrenaline play an important part in the birth process; there are many more hormonal influences on birth that are not well understood.
All mammals seek a safe place to give birth. This “nesting” instinct may be due to an increase in prolactin levels- prolactin is also sometimes referred to as the nesting hormone- or perhaps to a change in the balance between the female hormones oestrogen and progesterone that occurs soon before labour. At this stage,as you may have observed with your cat, interference which the nest- or more importantly with the feeling of safety-will stall the beginning of labour.
Researchers are not yet certain which hormone, or group of hormones, actually start the process of labour, but it is thought to be initiated by the baby, perhaps when the placenta reaches its limits in supplying nourishment and oxygen. The stress hormone cortisol, which also aids in maturing the lungs, seems to be involved. Oestrogen plays the important role of “wiring up” the uterus, so that it can contract in a well coordinated way in response to oxytocin during labour.
Even after labour has started, there are certain conditions that will stall, or even stop the process. If the flight-or-fight 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 obviously an advantage to stall labour when there is danger, and to seek safety. Many women have had the experience of their labour stopping when they entered the unfamiliar surroundings of a hospital.
Michel Odent cautions that even hunger, which also causes the body to release flight-or-fight hormones, can create difficulties with the establishment of labour. He advises women to eat- if they are hungry- in the earliest stages of labour; many hospitals have a policy which prevents labouring women from eating once they are admitted.
Oxytocin- the love hormone
Oxytocin causes the uterus to contract during labour. Levels of oxytocin gradually increase throughout labour to peak at around the time of birth, when it is thought to contribute to the euphoria and receptiveness to her baby that a mother feels after an unmedicated birth. This peak, which is triggered by sensations of stretching of the birth canal just before delivery, does not occur when an epidural is in place. Interestingly administration of an epidural has been found to interfere with bonding between ewes and their newborn lambs.
Synthetic oxytocin is often given by drip- that is, directly into the bloodstream- when labour contractions are inefficient. Oxytocin given in this way does not enter the brain, and therefore does not contribute to the post-birth “high”, and in fact can lead to a reduction in a mothers own oxytocin production by “negative feedback”. Sometimes midwives suggest nipple stimulation to improve contractions in labour, which, like breastfeeding, causes oxytocin levels to increase.
Oxytocin has another crucial role to play after the birth. Oxytocin causes the contractions that lead to separation of the placenta from the uterus, and its release as the “after-birth”. When oxytocin levels are high, strong contractions occur that reduce the chance of bleeding, or post-partum haemmorrhage.
Putting your newborn baby to your breast is the easiest way to increase oxytocin levels, but Michel Odent also emphasises the importance of privacy during the hour following birth. This gives the opportunity for uninterrupted skin-to-skin and eye-to-eye contact between mother and baby – conditions that are not often met in a hospital delivery room. One study showed that mothers who cuddled and suckled their babies in the first hour maintained higher oxytocin levels, interacted with their baby more at four days, were more tolerant to stress or monotony, had lower blood pressure and less body tension, and breastfed for longer.
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. As the hormone of orgasm, labour and breastfeeding, oxytocin encourages us to “forget ourselves”, either through altruism- service to others- or through feelings of love. Oxytocin, injected into specific parts of the brain, induces mothering behaviour in virgin animals.
The flight or flight hormones- sometimes referred to as catacholamines (pronounced cat-e-kol-a-meens), or CAs, because of their chemical structure- have an important role to play in the second stage of labour, which is when birth actually occurs. Michel Odent observes that during this second stage, a woman may express what he calls ‘physiological’ (or normal) fear, as well as having the dry mouth, dilated pupils and sudden burst of energy that are all characteristic of high levels of CAs.
This burst of CA’s gives a mother the energy to push her baby out, and Michel Odent observes that women are usually upright during this stage, often also having a sudden need to grasp something and bend at the knees. Some traditional cultures have used this flight-or-fight effect to help women having difficulty with the delivery by surprising or shouting out at this stage. It makes sense, at this point-of-no-return, for fear or danger to speed up the birth, so that mother and newborn baby can run for safety.
CA levels peak with the birth, then drop very quickly. High levels of CAs in animals have been shown to help with imprinting- the process which bonds mother to offspring-, so it may be assumed that CAs are part of the euphoric “hormonal cocktail” that a mother experiences in the first hour after an unmedicated birth. This steep drop in CA levels can make a mother may feel cold or shaky. At this stage a very warm atmosphere is essential, according to Michel Odent, to keep CA levels low and to allow oxytocin to work effectively.
The other major birthing hormone, prolactin, is most noteworthy for its effects after the birth. Prolactin levels are high during pregnancy, but its effects are blocked by the presence of other pregnancy hormones. With the expulsion of the placenta, prolactin’s effects are unblocked, and it becomes the major hormone of breast milk synthesis. Suckling by the newborn baby increases prolactin levels, and it is believed that 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.
Like the other hormones, prolactin has effects on emotion and behaviour. Prolactin stimulates ‘aggressive/defensive’ behaviour in new mothers- what I call the “tiger mother” effect. As well as this, prolactin helps us to put our babies needs first in all situations by increasing “submissiveness” and vigilance. When prolactin is combined with oxytocin, as it is soon after birth and during breastfeeding, it encourages a euphoric and selfless devotion to the baby that contributes to the mothers satisfaction and her baby’s health, both physical and emotional, and
Beta endorphin (pronounced beet-a en-door-fin)is one of the endorphin hormones which are released by the brain in times of stress or pain, and which are the bodies natural equivalents to opiate drugs like morphine and pethidine.
In pregnancy beta-endorphin levels are very high, and it may even play an important role in keeping women pregnant. During labour, beta-endorphin helps to relieve pain, and contributes to the “on another planet” feeling that most women have 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, but moderate levels of beta-endorphin are certainly helpful in labour. Endorphins have been shown to induce dependency and attachment. 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, endorphins, can induce a euphoric high, and are released during love-making 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 also 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 all your fear. You’ve packed your new nursing bra, and you know that prolactin will come to your aid as well. As you take your last look around the house, you catch the eye of your cat; lying down as her kittens attach to her nipples, she winks at you.