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Jun
01

Pain in Labor: Your Hormones Are Your Helpers

Author // Sarah J. Buckley, MD

Imagine this. Your cat is pregnant, due to give birth around the same time as you are. You have your bags packed for the hospital and are awaiting the first signs of labor with excitement and a little nervousness.

Meanwhile, your cat has been hunting for an out-of-the way place—your sock drawer or laundry basket—where she is 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 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 different shape of our pelvis and birth outlet due to 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.


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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 originate in deep and ancient parts of our brains and promote the physical processes of labor and birth. At the same time, they powerfully influence our emotions and behavior to make the journey to motherhood as smooth and pleasurable as possible for all mammalian mamas.

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 smooth, pleasurable, and even ecstatic, birth.

All mammals seek a safe place to give birth. This “nesting” instinct may be due to an 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 with the nest—or, more important, with the feeling of safety—can stall the beginning of labor.

Labor tends to start at night for day-living species, including women and our feline friends. This is likely related to lower levels of the labor-inhibiting fight-or-flight hormones adrenaline and noradrenaline, and also to the labor-promoting effects of melatonin, which we release at our usual sleep time.

Even after labor has started, there are certain conditions that will slow, or even stop, the process. If the fight-orflight hormones are activated by feelings of fear or danger, contractions can slow down. Our mammalian bodies are designed to give birth in the wild, where it is an advantage to postpone labor when the laboring female senses danger.

Similarly, many women have had the experience of their labor slowing, or even stopping, when they entered the unfamiliar surroundings of a hospital, and some of us can be as sensitive as a cat to the presence of an observer. Giving birth outside of our own familiar environment can cause the sorts of difficulties that captive animals experience when giving birth in a zoo.

Even hunger, which also causes the body to release fight-or-flight hormones, can stop labor from progressing, and it makes sense to eat if hungry in the earliest stages of labor. Generally, women (and cats) do not want to eat once labor is established, but every woman is different.

Labor and birth involve a complex orchestra of birthing hormones. This includes: oxytocin, sometimes called the hormone of love; beta-endorphins, the body’s natural pain-killers; the fight-or-flight hormones adrenaline and noradrenaline (epinephrine and norepinephrine), along with the stress hormone cortisol; and prolactin, the major hormone of breast milk production. There are many more hormonal influences on birth that are not well understood.

Oxytocin is made in the laboring mother’s brain and released into both her brain and body. Oxytocin levels increase (as measured in the blood) and coordinate the rhythmic contractions of labor. At the same time, oxytocin elevations in the brain give natural calming and painrelieving effects that counter labor’s stresses.

Oxytocin levels are even three to four times higher around the time of birth, triggered by the sensations of stretching of the birth canal as the baby is born. This also causes peak oxytocin levels in the brain, which powerfully activate the reward and pleasure centers as the mother meets her offspring for the first time. This activation not only feels good, but it also ensures that the new mother will be rewarded and motivated to give the dedicated mothering that human babies, kittens, and all mammalian newborns require.

This system can be disrupted by birth interventions. For example, when an epidural is in place, the loss of sensations leads to reduced oxytocin in the brain and body. This can slow labor and cause difficulties at the pushing stage. The reduction in brain oxytocin can reduce the feelings of pleasure and ecstasy that help the new mother fall in love with her baby.

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 “afterbirth.” When oxytocin levels are high, strong contractions reduce the chance of bleeding, or postpartum hemorrhage.

Putting your newborn baby to your breast is the easiest way to increase oxytocin levels. However, oxytocin is a “shy” hormone, so it is important to feel private and safe during the hour or so following birth. Uninterrupted skin-to- skin contact with your newborn will also help to optimize oxytocin release and reduce the chances of bleeding.

The postpartum oxytocin surge also opens up superficial blood vessels on the new mother’s chest and breasts, giving a very effective warming system for her skin-to-skin baby.

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 open and receptive to social contact and support. As the hormone of labor and breastfeeding, oxytocin brings feelings of love and connection that will help through the years of mothering.

Synthetic oxytocin can be given by intravenous infusion directly into the bloodstream to speed labor. It is commonly administered following an epidural to counter the slowing of labor due to the reduction in natural oxytocin. It causes longer, stronger contractions, but does not enter the brain, and so does not have the calming, pain-relieving effects of natural oxytocin.

When administrated at high doses for a prolonged period, synthetic oxytocin can cause reduced sensitivity in the laboring woman’s uterine oxytocin system due to a reduction in her uterine oxytocin receptors. This increases her risk of bleeding after the birth.

The fight-or-flight hormones—also called catecholamines, or CAs—can interfere with oxytocin release during labor and after the birth. However, they have an important role to play in the pushing (second) stage of labor, which is when birth actually occurs.

At this time, when her cervix is fully open but the urge to push may not be strong, a woman can feel the need to rest for some time. This is sometimes known as the “rest and be thankful” time. After this, she may quite suddenly experience the dry mouth, dilated pupils, and sudden burst of energy that are all characteristic of high levels of CAs.

This gives a mother the energy to be upright and push her baby out. Michel Odent observes that some traditional cultures have used this fight-or-flight effect to help women having difficulty at this stage by surprising them, or shouting out. It makes sense, at this point-of-no-return, for fear or danger to speed up the birth, so that a mother can gather up her newborn baby and run for safety.

The new mother’s CA levels drop quickly after the birth, which can make her feel cold or shaky. At this stage a warm, private, safe atmosphere, with unlimited contact with her baby, will help to keep her CA levels low and allow oxytocin to work effectively to prevent bleeding.

Prolactin is the major hormone of breast milk synthesis, and levels are increased at the end of labor, likely in preparation for breastfeeding. Suckling by the newborn baby increases prolactin levels. Early and frequent suckling from the first days makes the breasts more responsive to prolactin, which in turn helps to ensure a good long-term supply of milk.

Beta-endorphins are released in the brain in times of stress or pain, and give natural pain relief, equivalent to drugs like pethidine/meperidine. Beta-endorphins help us to deal with pain in labor, as well as supporting the altered state of consciousness that will encourage us to follow our instincts. As part of the hormonal cocktail after birth, beta-endorphins play a role in bonding between mother and baby, who is also primed with endorphins from the birth process. Endorphins are actually present in breast milk, which explains the natural high that babies can get after they breastfeed.

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.


Pathways Issue 10 CoverThis article appeared in Pathways to Family Wellness magazine, Issue #10 and #64.

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