Four major hormonal systems are active during labor and birth. These involve oxytocin, the hormone of love; endorphins, hormones of pleasure and transcendence; adrenaline and noradrenaline (epinephrine and norepinephrine), hormones of excitement; and prolactin, the mothering hormone. These systems are common to all mammals and originate deep in our mammalian or middle brain. For birth to proceed optimally, this part of the brain must take precedence over the neocortex, or rational brain. This shift can be helped by an atmosphere of quiet and privacy with, for example, dim lighting and little conversation, and no expectation of rationality from the laboring woman. Under such conditions a woman intuitively will choose the movements, sounds, breathing, and positions that will birth her baby most easily. This is her genetic and hormonal blueprint. All of these systems are adversely affected by current birth practices. Hospital environments and routines are not generally conducive to the shift in consciousness that giving birth naturally requires. A woman’s hormonal physiology is further disturbed by practices such as induction, the use of pain killers and epidurals, cesarean surgery, and separation of mother and baby after birth.
Hormones in Birth
Oxytocin, The hormone of love
Perhaps the best-known birth hormone is oxytocin, the hormone of love, which is secreted during sexual activity, male and female orgasm, birth, and breastfeeding. Oxytocin engenders feelings of love and altruism; as Michel Odent says, “Whatever the facet of love we consider, oxytocin is involved.”1 Oxytocin is made in the hypothalamus, deep in our brains, and stored in the posterior pituitary, the master gland, from where it is released in pulses. It is a crucial hormone in reproduction and mediates what have been called the ejection reflexes: the sperm ejection reflex with male orgasm (and the corresponding sperm introjection reflex with female orgasm); the fetal ejection reflex at birth (a phrase coined by Odent for the powerful contractions at the end of an undisturbed labor, which birth the baby quickly and easily2); and, postpartum, the placental ejection reflex and the milk ejection, or let-down reflex, in breastfeeding. As well as reaching peak levels in each of these situations, oxytocin is secreted in large amounts in pregnancy, when it acts to enhance nutrient absorption, reduce stress, and conserve energy by making us more sleepy.3 Oxytocin also causes the rhythmic uterine contractions of labor, and levels peak at birth through stimulation of stretch receptors in a woman’s lower vagina as the baby descends4. The high levels continue after birth, culminating with the birth of the placenta, and then gradually subside.5 The baby also has been producing increasing amounts of oxytocin during labor;6.7 so, in the minutes after birth, both mother and baby are bathed in an ecstatic cocktail of hormones. At this time ongoing oxytocin production is enhanced by skin-to-skin and eye-to-eye contact and by the baby’s first attempts at suckling.8 Good levels of oxytocin will also protect against postpartum hemorrhage by ensuring good uterine contractions. In breastfeeding, oxytocin mediates the let-down reflex and is released in pulses as the baby suckles. During the months and years of lactation, oxytocin continues to act to keep the mother relaxed and well nourished. Oxytocin expert and researcher Professor Kerstin Uvnas Moberg calls it ‘…a very efficient anti-stress system, which prevents a lot of disease later on. In her study, mothers who breastfed for more than seven weeks were calmer,when their babies were six months old, than mothers who did notbreastfeed. Outside its role in reproduction, oxytocin is secreted in other situations of love and altruism, for example, sharing a meal.9 Researchers have implicated malfunctions of the oxytocin system in conditions such as schizophrenia,10 autism,11 cardiovascular disease,12 and drug dependency,13 and have suggested that oxytocin may mediate the antidepressant effect of drugs such as Prozac.14
Beta-endorphin: natural pain relief
As a naturally occurring opiate, beta-endorphin has properties similar to pethidine (meperidine, Demerol), morphine, and heroin, and has been shown to work on the same receptors of the brain. Like oxytocin, beta-endorphin is secreted from the pituitary gland, and high levels are present during sex, pregnancy, birth, and breastfeeding. Beta-endorphin is also a stress hormone, released under conditions of duress and pain, when it acts as an analgesic and, like other stress hormones, suppresses the immune system. This effect may be important in preventing a pregnant mother’s immune system from acting against her baby, whose genetic material is foreign to hers. Like the addictive opiates, beta-endorphin induces feelings of pleasure, euphoria, and dependency or, with a partner, mutual dependency. Beta-endorphin levels are high in pregnancy and increase throughout labor,15 when levels of beta-endorphin and corticotrophin (another stress hormone) reach those found in male endurance athletes during maximal exercise on a treadmill.16 Such high levels help the laboring woman to transmute pain and enter the altered state of consciousness that characterizes an undisturbed birth. Beta-endorphin has complex and incompletely understood relationships with other hormonal systems.17 In labor, high levels will inhibit oxytocin release. It makes sense that when pain or stress levels are very high, contractions will slow, thus ‘…rationing labor according to both physiological and psychological stress.18 Beta-endorphin also facilitates the release of prolactin during labor;19 prolactin prepares the mother’s breasts for lactation and is thought to be important in preparing the baby’s lungs and heat-regulating systems for life outside the womb.20.21 Beta-endorphin is also important in breastfeeding. Levels peak in the mother at 20 minutes,22 and beta-endorphin is also present in breast milk,23 inducing a pleasurable mutual dependency for both mother and baby in their ongoing relationship.
Fight-or-Flight Hormones: the body response to stresses
The hormones adrenaline and noradrenaline (epinephrine and norepinephrine) are also known as the fight-or-flight hormones, or, collectively, as catecholamines (CAs). 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. In the first stage of labor, high CA levels inhibit oxytocin production, therefore slowing or inhibiting labor. CAs also act to reduce blood flow to the uterus and placenta, and therefore to the baby. This makes sense for mammals birthing in the wild, where the presence of danger would activate this fight or flight response, inhibiting labor and diverting blood to the major muscle groups so that the mother can flee to safety. In humans, high levels of CAs have been associated with longer labor and adverse fetal heart rate patterns (an indication of stress to the baby).24 After an undisturbed labor, 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 fetal ejection reflex. The mother experiences a sudden rush of energy; she will be upright and alert, with a 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.25 Some birth attendants have made good use of this reflex when a woman is having difficulties in the second stage of labor. For example, one anthropologist working with an indigenous Canadian tribe recorded that when a woman was having difficulty in birth, the young people of the village would gather together to help. They would suddenly and unexpectedly shout out close to her, with the shock triggering her fetal ejection reflex and a quick birth. After the birth, the mother’s CA levels drop steeply. A warm atmosphere is important; a new mother is very sensitive to temperature and if she cools down significantly, the cold stress will keep her CA levels high, inhibiting her natural oxytocin release and therefore increasing her risk of postpartum hemorrhage.26 Noradrenaline, as part of the ecstatic cocktail, is also implicated in instinctive mothering behavior. Mice bred to be deficient in noradrenaline will not care for their young after birth unless noradrenaline is injected back into their system.27 For the baby also, birth is an exciting and stressful event, reflected in high CA levels. These assist the baby during birth by protecting against the effects of hypoxia (lack of oxygen) and subsequent acidosis.28 High CA levels at birth ensure that the baby is wide-eyed and alert at first contact with the mother. The baby’s CA levels also drop rapidly after an undisturbed birth, being soothed by contact with the mother.
Prolactin, Hormone of submission or surrender
Known as the mothering hormone, prolactin is the major hormone of breast milk synthesis and breastfeeding. Levels of prolactin increase in pregnancy, although milk production is inhibited hormonally until the placenta is delivered. Levels decrease during labor but then rise steeply at the end of labor and peak with birth. Prolactin is a hormone of submission or surrender–in primate troops, the dominant male has the lowest prolactin level–and produces some degree of anxiety. In the breastfeeding relationship these effects activate the mother’s vigilance and help her to put her baby’s needs first.29 Prolactin has been associated with nurturance from fathers as well as mothers, earning the additional label “The hormone of paternity”30. New fathers with higher prolactin levels more responsive to their babies’ cries.31 Animal studies show that prolactin release is also increased by carrying infants32. The baby also produces prolactin in pregnancy, and high levels are found in amniotic fluid, secreted by the baby’s membranes as well as the mother’s uterine lining.33 Prolactin is also secreted into breastmilk, at least in the rat.34 According to one researcher,“… there is evidence that prolactin plays an important role in the development and maturation of the neonatal [newborn] neuroendocrine [brain-hormone] system.”35
Undisturbed Birth is exceedingly rare in our culture…
Undisturbed birth is exceedingly rare in our culture, which reflects our ignorance of its importance. Two factors that disturb birth in all mammals are firstly being in an unfamiliar place and secondly the presence of an observer. Feelings of safety and privacy thus seem to be fundamental. Yet the entire system of Western obstetrics is devoted to observing pregnant and birthing women, by both people and machines, and when birth isn’t going smoothly, obstetricians respond with yet more intense observation. It is indeed amazing that any woman can give birth under such conditions. Some writers have observed that, for a laboring woman,having a babyhas a lot of parallels with making a baby: the same hormones, the same parts of the body, the same sounds, and the same needs for feelings of safety and privacy. How would it be to attempt to make love in the conditions under which we expect women to give birth? When I gave birth to my fourth baby, Maia Rose, I arranged a situation where I felt very private, safe and undisturbed, and had my easiest and most ecstatic labor and birth: one-and-a half hours with an unexpectedly breech baby. I believe that this birth proceeded optimally because of this lack of disturbance, and because of my freedom to follow my own instincts. Undisturbed birth is possible in a variety of settings, but must always involve a feeling of emotional security for the birthing woman. A familiar and supportive companion, such as a midwife or doula, can play an important role in creating and protecting a private space for the laboring woman, especially in a hospital setting.
© Dr Sarah J Buckley – First published in Mothering magazine 2002
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