During labor, you want contractions that are longer, stronger, and closer together. But why? Dr. Sarah Buckley and Adriana take a deep dive into the amazing and fascinating hormonal dance that happens during the birthing process, and how interventions such as synthetic oxytocin or an epidural can lead to a cascade of interventions that negatively impact the process for both the birthing person and their baby. They also talk about ways to support the physiology of birth (regardless of what path it takes) in order to help fill any “hormonal gaps” that may occur.
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- Hormonal Physiology of Childbearing report, by Sarah for Childbirth Connection (now hosted by the National Partnership for Women & Families)
- Pain in Labour: Your hormones are your helpers, by Sarah Buckley
- The Role of Hormones in Childbirth, Childbirth Connection
- Sarah Buckley’s “Hormonal Physiology of Childbearing: Evidence and Implications for Women, Babies, and Maternity Care,” a review for birth educators and doulas, by Penny Simkin
- Orgasmic Birth (and the shorter adaptation Organic Birth: Birth is Natural!), from Debra Pascali-Bonaro
- Gentle Birth, Gentle Mothering: A Doctor’s Guide to Natural Childbirth and Gentle Early Parenting Choices, by Sarah Buckley
Related Birthful episodes:
- The Baby’s Birth Experience
- Your Baby, The Mammal
- How to Avoid a “Cascade of Interventions”
- Third Stage of Labor
- [Breastfeeding] Epidurals and Breastfeeding, What’s the Connection?
- [Postpartum] Hormones After Birth
- Why Employers Need to Value Your Parenting Skills
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Helping Your Mammalian Body (and Baby!) Have an Easier and More Connected Birth
Adriana Lozada: Hello, hello, Mighty Parent or Parent-To-Be! Welcome to Birthful. I’m Adriana Lozada, and as we forge on in our series about Birth Beyond The Clinical Experience, today we’re going to take a deep dive into the amazing and fascinating hormonal dance that happens during the birthing process. We’re also going to take a look at the protagonist role of oxytocin in not only bringing on contractions, but also helping you cope with the intensity so that you and your baby are more ready to fall in love, and we’ll also look at what all of this has to do with your motivation to take care of your baby.
My guest for this is none other than Dr. Sarah Buckley who has spent years, years deep in research, studying the hormones of physiological labor and birth along with how they are impacted by interventions and part of our conversation will be on how you may experience this physiological flow of hormones in your body, but also what happens to the physiology when you have, say, an induction, an epidural, or a pre-labor cesarean. And of course, your hormonal experience is tightly intertwined with what your baby experiences during the birth process, and so we’re also going to talk about how these hormonal changes help get your baby ready for the outside world, and what you can do to help fill in any hormonal gaps that may be brought on by interventions. This is such a mind-blowing and jam-packed episode that you may want to listen to it more than once. You’ve been forewarned.
You’re listening to Birthful. Here to inform your intuition.
Adriana: Welcome, Dr. Sarah Buckley. It is so lovely to have you on the show. I’m really excited about this conversation we’re gonna have today. But before we start, why don’t you tell the listeners a little bit about yourself. Where are you from? How do you identify?
Sarah Buckley: Thanks so much, Adriana. It’s a pleasure to be here. I’m a GP, a family physician by training. I live in Brisbane, Australia, which is a beautiful subtropical city on the east coast of Australia. I’m medically trained, as I mentioned, and currently I’m doing a PhD looking at oxytocin and childbirth from all kinds of different perspectives.
Another important thing about me is I had four children all born at home. And they were such positive experiences, that’s really what propelled me into this type of work. I’m the author of the book, Gentle Birth, Gentle Mothering, and also in 2015, I wrote an extensive report called Hormonal Physiology of Childbearing. And you could say my PhD is like an update to that and an expansion of that as well.
Adriana: Well, and I love how deeply you’ve gone into the research of the hormones and the physiology of birth and, trying to really get to all these unknowns, right? I mean, there’s still so many unknowns, like: Why does birth start? I’ve heard you say we still don’t know that, but you have sussed out so many things that are vitally important and given birth workers and, everybody who’s read your report, that knowledge of like, “Oh, this makes sense”. Of course the body would build in redundancies, and of course the body would have ways to make this work even if nobody were around. And so I think what I wanted to do with our conversation today is talk about that experience of birth from the hormonal point of view. How does that dance happen and what can people expect?
Sarah: Well, I think the first thing to say is that we are mammals. We have mammary glands. We suckle our young, so the way that we give birth is really very similar to all of our mammalian cousins. And a mammalian birth has evolved over 65 million years. And for almost all of that time, even humans were giving birth in the wild.
So birth has evolved to be successful in the wild where there’s no fences, no walls, and the birthing female is very vulnerable to predators. So that really explains a lot of how birth works, and also when birth doesn’t work. Because if you think about any mammal giving birth in the wild, it’s critical that she’s at a safe place because she’s not going to be able to defend herself easily against predators, and she’s gonna be very attractive, because she’s making strange noises, there are smells, the blood, the amniotic fluid, the baby… all of those things would attract predators. So she has to know she’s in the safest place possible. So, her subjective sense of safety is critical. So birth works best when women, like all mammals, feel safe, right? And feeling safe at a very basic brain level at our limbic system.
So it’s not an intellectual idea, like going to hospital or having an obstetrician is the safest way. It’s really, you know, it’s a primal sense of safety, and that primal sense of safety is really triggered when we are in unfamiliar surroundings, when we’ve got unfamiliar people, unfamiliar noises, even things that we see that are not familiar. So being in a familiar place is really the kindest thing we can do to our limbic system in relation to labor and birth.
Adriana: Right! And it’s not something that, like you said, that we’re thinking about. It really has to come from that viscera— from your body at a level that you can’t really control.
Sarah: That’s exactly right. And some women will kind of prowl around in labor almost like an animal, looking for the safest place. And often where women will choose to give birth is like the smallest room they can find, which is the shower or the toilet or something like that. And they’ll choose to be with people that they know. I mean, it’s a very unusual situation for modern birthing women to be in a strange place with strange people.
And just going back to some of the science around it, it really explains where there’s so many benefits to having at least someone there that you know, like your own doula, supportive birth companion, your own midwife— continuity of midwifery care, having the same midwife through pregnancy, through labor and birth, and afterwards— it’s a recipe for feeling safe and feeling safe is a precondition for the oxytocin system as well.
Adriana: Right. So then that was gonna be my question: So why does the body need to be feeling safe in order for this birth to happen?
Sarah: Yes, well… I’ve explained it from an evolutionary point of view and if we sort of start talking about the hormones now. So oxytocin is, Michel Odent calls it “the shy hormone.” We don’t release it easily when we don’t feel safe. So, you know, making a baby involves a lot of oxytocin and we certainly need to feel safe there. You know, socializing with people. That involves oxytocin as well. We do that more likely, more easily when we feel safe. So oxytocin is a hormone that was first discovered as oxy- = fast, –tocin = birth, the hormone that makes birth go fast. But subsequently, we’ve discovered so many things about it in the last a hundred plus years, and we know that oxytocin is actually made in the brain and released from the brain into the body and during labor and birth— and a few other situations I’ll describe in a minute— it goes into the bloodstream, finds its way to the uterus. It actually finds what we call the oxytocin receptors, which are on the outside of the uterine muscle cell. And when oxytocin binds to its receptor, it’s like putting a key into a lock. It turns the key and then it sends a chemical message into the cell saying contract. And that’s what’s happening during labor. We’re releasing oxytocin from our brain, actually from the pituitary gland, impulses to the uterus, and then the rhythmic contractions of labor are happening.
But at the same time, and this is really what we’ve discovered more recently about oxytocin, it has a myriad of effects. Within the brain, it’s actually what we call a neuromodulator. It modulates or changes a whole lot of settings we could say in the brain. So in terms of labor and birth, it makes us feel calmer. It really reduces fear and stress. It also has pain-relieving effects, which is very helpful in labor and birth as well. And at the same time, it switches on during labor and birth, what we call the “pleasure and reward centers” in the brain. These are the dopamine pathways. And the reason it’s doing that is because straight after birth, the mother and any mammalian mother is gonna meet her babies for the first time, and Mother Nature does her best at making sure that’s a positive experience.
I say it’s like the best first date ever, because the mother’s brain, pleasure and reward centers are maximally activated. And then she gets the sensations of her babies, the smell, the sight, the taste. Most mammals lick their babies, a touch of her babies. And those things get connected up, we say “fired and wired” together. So that from the first meeting, her baby’s resource of pleasure and reward, and that’s gonna motivate her to give that dedicated care that every mammalian newborn needs. So that’s kind of basic mammalian birth physiology and oxytocin is a mammalian hormone. So it’s very, we could say, efficient and effective that at the same time that oxytocin is causing the contractions of labor, it’s also preparing the mother and the mother’s brain in particular for meeting her babies on the next stage of species survival basically.
And the other thing I say about oxytocin, that’s important to know, apart from the brain and the receptors, is that oxytocin perpetuates what I call the “snowball of labor.” So labor is an event that starts small, becomes bigger and bigger, and in the end becomes virtually unstoppable, like a snowball. And the reason it has this pattern is because labor involves what we call “positive feedback loops.” “Feed forward cycles” is another term for that.
So the opposite of that is negative feedback loops, and that’s all of us sitting here— you know, if we hear a strange noise, my dog just barked, you know, I can get a burst of adrenaline, it puts my heart rate up, it puts my blood pressure up— I’m ready for fight or flight. My body detects those signals, my heart rate’s higher than it needs to be right now and it brings it down. That’s a negative feedback. And that keeps my body even, all my body processes even— that’s good homeostasis.
But that… it’s not like that in labor. Labor is not homeostatic, as I said. Labor starts small, gets bigger and bigger, becomes unstoppable because of positive feedbacks.
An important one, involving oxytocin in the process of labor is what people might know as “the Ferguson reflex.” So what’s happening all through labor is as the baby’s going lower, it’s pressing on the mother’s cervix, lower uterus, lower vagina, and those sensations, which are quite intense, if you’ve given birth you’ll recognize that. Those sensations are actually fed back to the brain by a specific nerve pathway. And when that information from those sensation reaches the brain, the brain actually releases more oxytocin, and that oxytocin comes from the brain through the bloodstream, back to the uterus, binds with the receptors causes, stronger contractions, more sensations, and then more release from the brain. So that’s a positive feedback cycle.
And that’s one of the positive feedback cycles that has labor be an accelerating process. And it’s also very effective and efficient— you know, as labor progresses, it gets bigger and bigger. And then at the pushing stage we get these very strong contractions, strong sensations, you might have noticed, a lot of feedback and a lot more oxytocin. So it also helps us to have an efficient and effective pushing stage. You get our babies out as quickly as possible.
If we go back to that evolutionary model, any animal, the pushing stage in the wild is especially dangerous. So Mother Nature builds in these processes to make sure that the pushing stage in particular is as efficient and effective as possible.
And all that time that this positive feedback loop is happening, we’re also getting that release not just from the brain, but also into the brain. So all those calming, connecting, pain, relieving, switching on reward and pleasure center effects are happening, even more as time goes on to help any mammalian mother to, you know, to get too unsettled by labor to not have an aversive experience. You know, Mother Nature wants it to be a positive experience, and most animals don’t go to classes to learn. You know, it has to happen through the processes of labor and birth, and that’s part of what I call Mother Nature’s superb design.
Adriana: And I think it’s really important to note that, because when we put birth in the hospital, then we start having all these medical checks and making sure things are being measured and cervical checks, but the body doesn’t care about any of that. So what I’m hearing is that progress in labor, from a mammalian point of view, it’s kind of tuning into is it getting longer, stronger? Are contractions closer together? Like: Is it building? Are these loops really working?
Sarah: That’s right! That’s right. And I’ve got to also say that, you know, labor isn’t… I mean, we put it on a partogram, near the little graph they fill out in hospital of how many centimeters dilated your cervix is, and how strong your contractions are. And it’s kind of expected to go in a linear way. But you know, most biological processes aren’t linear. If you’ve watched a child develop, you know that they are crawling and it might take a very long time. Some children, until they walk, and some children, it’s not very long. Like everyone has their own individual pattern and just going back to what you said before that the pattern of labor, we would have to say reflects the feelings of the woman, of the birthing female.
Is she safe? If she feels safe, it’s gonna go pretty well. If she doesn’t feel safe, it may slow down. And many women have had that experience of starting labor at home. It’s all going well. They feel like they’re almost ready to give birth, they get to hospital and everything slows down or stops and that’s exactly what we are talking about.
At this limbic system, primitive brain level, that birthing person doesn’t feel safe. So, you know that feeling of safety is so essential during labor and birth. So, you know, one takeaway from this is what I say the basic needs of the laboring woman is that she feels private, that she feels safe. And actually, if you think about mammals birthing in the wild, is that she feels unobserved.
So, you know, the most skillful birth attendants, which are generally midwives, are skillful for supporting physiological birth, really know how to observe without being obvious. They know where a woman is in labor by the sound she’s making, by the way she’s moving, you know, and we’ve superimposed on that, as you say, the cervical examinations and that is quite disruptive to women. It’s not a safe feeling to have someone you don’t know put their hand in your vagina, right? So how do all those things and all those observations that we do in hospital contribute to the progress of labor and birth? Probably in a negative way, we would have to guess.
Adriana: Well, and we know… I mean, if you look at the work of Michel Odent, which I know you’re a big fan of his amazing work, also saying that observation/feeling observed is one of those things that triggers your neocortex— triggers your thinking brain— which then if you are thinking, it’s hindering those mammalian activities of these hormone secretions, because it’s not letting your body just do the birthing. Like, if you’re thinking, you’re not birthing… and back and forth.
Sarah: Yes, that’s exactly right. We really have to sink into the limbic system, not just for that assessment of safety, but that’s kind of where it’s all happening. That’s where oxytocin’s being released from. That’s where we’re gauging what’s going on. And for women that really feel unobserved and free to move in labor, it’s a very primal, it’s an almost animalistic process. Women will prowl around. They’ll behave in strange ways. They’ll let people know exactly what they want and don’t want. And that’s really the recipe for an effective and efficient labor and birth is being able to get into our primal nature and let all those hormones just flow. I mean, it’s like good sex really.
You know, when we have really good uninhibited sex, we get into that not-thinking, that primal kind of animalistic body nature. And that’s really what promotes an efficient labor in birth as well.
Adriana: I find that also your body is kind to you. I’m so glad you mentioned that. You reminded us that birth is not linear, because as a doula I’ve seen it— I’ve seen labors that take so, so long to get to,whatever, five centimeters and then suddenly there’s a baby in an hour. But I’ve seen this more in homebirths; hospital births don’t kind of allow for this where labor will start and stop.
And one anecdote that comes to mind is a client who was having contractions overnight, and then in the morning, she had older kids, so to get her kids out to school labor sort of went back burner and got them ready for school and they left and during the day she was doing things, contractions were less, right? And when her kids came back at 3:00 p.m., they stopped and got dinner ready. They ate, she went to bed, contractions were nowhere to be seen. And then at 3:00 a.m. she woke up, her water broke and had a baby in an hour.
Sarah: So effective and efficient, isn’t it, for what she has to do in the rest of her life? I mean, that’s a perfect illustration really of that interaction between the sense of, well, we couldn’t say safety ‘cause she probably feels safe, but, you know, she probably doesn’t feel in a little nest until the children are settled right in their own space.
Adriana: Such a good interaction. So then in these feedback loops, we talked about how people want to get into places that they feel safe, usually not observed where they can just let go and be able to be vulnerable and let the body do what it needs to do.
How does that match when we take it into the mostly medicalized spaces where we give birth? If you’re not in a birth center or at home, how can you support your hormonal processes in that environment that is not conducive and is so interruptive?
Sarah: Yes, that’s a really important question. So, you know, if we look at the research, as I mentioned, you know, the two things that really help with that is having continuity of care with your own midwife— so a midwife that you feel safe with that looks after you in pregnancy, during labor and birth and postpartum as well.
So just an anecdote from myself: I had my first baby at home, and she was a little bit ahead of schedule and I had a fast labor, and I remember that time of thinking, “Oh my God, this is gonna happen,” and being scared, having this fear. And my, at that point, my midwife walked in and I just looked in her eyes and there was this transmission of safety.
Like, I knew this woman, she knew me. I’d had all these consultations in my pregnancy. We knew each other, what we wanted, what I wanted. We had this almost like physical connection with each other. And that transmission that transmitted to me through that gaze that happened, and I felt safe when I had my baby like 15 minutes later.
So that sense of safety of being with someone. So, taking your own midwife, taking your own doula, supportive birth companion, has the same effect as well, the same benefits of reducing the needs for almost every intervention and increasing satisfaction. So that’s one thing.
The second thing I want to mention is using the snowball of labor to your own benefit. So remember I said labor gets bigger and bigger and in the end becomes virtually unstoppable? Well, you wanna go to hospital when your labor is virtually unstoppable because as I mentioned, often you go to hospital and labor’s going pretty well at home and you go to hospital and it stops. But there is a point in labor where you can’t stop it, where the snowballs just sort of gonna go on and on.
And there is actually, like, a hormonal theory for that. And the theory, well that, the evolutionary context for that is if you think of a mammal giving birth in the wild, early in labor, predator turns up, you get a fight or flight reaction or for women, you go to hospital where you are not safe in that limbic system way.
And, you know, everything slows down. So you, and you go and find a safe place. Or in hospital you… help you to make your environment feel safer. You settle in and then things can start again. But at the end of labor, if you imagine a mammal birthing in the wild at the end of labor, and a predator turns up and she’s almost pushing her baby out, it’s too late to stop, right? You can’t just suddenly stop that. So what tends to happen is that flood of adrenaline, that flood of fight or flight hormones, tends to actually accelerate labor at that stage. And it’s kind of connected to a little bit of what I described, can be physiological fear, even without fear from the outside.
You can feel a little bit of fear when you get to that transition and the fight or flight hormones kick in, but in a sense of stress and change and like moving into hospitals, sometimes that extra stress and the fear of not being in this safe, familiar environment can actually trigger the end of labor and the baby can be born as soon as you walk in the door, like. ten minutes after you arrive. That’s also a common story.
So using that snowball of labor and going to hospital at the last minute so that you’re not there for very long and there’s no time to do any of those interventions and you don’t need them. So that’s my number two. Number two, hint.
But the third one is to pay attention to your limbic system. So the limbic system is this primitive brain and it’s always scanning, “Is this place safe?’ And the way that it discerns if the place is safe is through our senses— you know, our sight, our hearing, our taste, our smell, our touch.
So how can we protect our senses in that transition to hospitals? So like having a pillow or an eye mask to protect, you know, your vision, so you’re not seeing all these unfamiliar things. Having a familiar smell… I mean, smell is very connected to the limbic system, actually to oxytocin. So some people take in a smell that they like, a smell that they’re familiar with, the smell of their partner, you know, that kind of thing.
So smell and hearing, you know, wearing headphones, that’s where people have used certain tapes or hypnobirthing tapes that they’re familiar with, and then they play those in labor. So using the senses to protect yourself and to kind of reassure your limbic system really, that you are in a safe place.
So those are, those are my hints for, helping to feel private, safe, and unobserved in any situation.
Adriana: Love those! And that connection with also you mentioned the hypnobirthing tapes, of connection to mindfulness. I find that people that have a mindful practice during pregnancy and have… Can easily access those deeper brainwaves, have that practice installed, seem to be able to access them quicker when they’re in the throes of labor or in this situation that you mentioned, like going to a hospital and wanting to feel safe again and can more easily, shut off that thinking brain as well.
Sarah: That’s interesting because that’s also— and this is actually a function of oxytocin that I didn’t mention— that oxytocin is a neuromodulator. So it shifts processes in the brain. And one of the things that oxytocin does is it shifts us out of our sympathetic fight or flight alertness system, and it shifts us into our parasympathetic, which is our calm and connection, relaxation thing.
And what you’re describing really is people that can shift from the stress system into the parasympathetic, the calm system, and that’s actually part of the processes of labor and birth as well. Like the parasympathetic nervous system actually promotes contractions as well. And the sympathetic nervous system kind of inhibits contractions.
So oxytocin is helping us to get there. But as you say, we can use our circumstances, we can use training, you know, brain training, really like mindfulness to help us to get into the parasympathetic nervous system and labor as well.
Adriana: So then if we’re talking about oxytocin, we have to talk about synthetic oxytocin too, because I feel like the rate of inductions is steadily increasing, and I read that it was close to 50% of people will have either some sort of exposure to synthetic oxytocin, be it an induction or an augmentation. Do the two act the same? How do they differ?
Sarah: Yes. Well, those are all good questions, and we’ve actually just published a paper as part of my PhD research about synthetic oxytocin. In the paper, we— actually, it’s called a systematic review, so we did a structured process that allowed us to find all the papers that have been published in a particular area.
So we found all the papers that had been published where they measured women’s oxytocin levels in their blood when they were having synthetic oxytocin in labor. And we also found papers that measured newborn oxytocin levels when their mothers had had synthetic oxytocin infusions in labor and it’s very interesting to see how all that marries together.
Synthetic oxytocin and natural oxytocin are actually exactly the same molecule, so that if a woman’s having synthetic oxytocin and we measure her blood, we can only find oxytocin, you know, whether it’s her own or the synthetic version, we don’t know ’cause it’s exactly the same molecule. So, it is exactly the same molecule.
But everything that I’ve talked about oxytocin, really, is different from synthetic. Because it’s made in the brain and released into the brain, it has these calming connecting, pain relieving, reward and pleasure center activating pleasurable effects. But synthetic oxytocin, we don’t administer it into the brain, right? We administer it to the body.
Adriana: Thank goodness.
Sarah: Through an infusion. So we give it into the body. And into the body, yes, it causes oxy- = fast, -tocin = birth. It makes the contraction stronger, and it makes them closer together, but it doesn’t go into the brain. And what that means is we get these stronger contractions. We don’t get the parallel increase in brain oxytocin that helps us to cope with those stronger contractions.
So generally having synthetic oxytocin in labor, whether it’s for an induction or whether it’s for speeding up labor (as we say, augmenting labor), it really is more stressful, it’s more painful.
And the other problem with synthetic oxytocin, is it tends to trigger what’s been called the “cascade of interventions,” because you’re getting these stronger contractions often at the beginning of labor before you’ve had a chance to kind of build up your natural pain relieving processes.
And because you’re not getting that brain help, you tend to get stronger, more painful contractions, and you generally need some strong pain relief, like an epidural. So, the cascade of intervention often starts with synthetic oxytocin, and then you have the epidural, and then that has consequences for your oxytocin system, and then you end up having difficulty pushing your baby out. And then you might even need a cesarean as well, so one intervention has led to a whole lot of other interventions.
And some of these are kind of, we say, filling in the hormonal gap because, as I said, natural oxytocin, the pain relieving effects builds up as the contractions build up. But we’ve kind of separate those things— we’ve got strong contractions without the pain relieving effects— we’ve caused a hormonal gap in the brain mix, would say, and then we need to fill that with some kind of other pain relieving effect.
Adriana: Well, and it’s almost because those intense contractions and close to other contractions are kind of happening much earlier, you tend to have them for much longer. Right? Meaning it’s sort of the goal is to get contractions to be every two to three minutes lasting a minute and a half to two minutes. So about five contractions in ten minutes, no more than that. That’s the sort of protocol gauge that I’ve seen, but they’re trying to get to that pattern as soon as possible, which sometimes the body is only a little bit dilated, which means that then they’re holding that contraction pattern for many, many hours, whereas with, physiological, endogenous, body-made oxytocin, that sort of contraction pattern, that intensity would only be when, as you mentioned before, it was, like, unstoppable, not at the beginning.
Sarah: That’s right. The snowball’s too big early in labor is the problem, exactly. I think that’s true. And yeah, as you say, we haven’t built up our own endogenous pain relief. And the other problem is, as we mentioned, the contractions are stronger, but they’re also closer together than our natural contractions are.
And the important thing about contractions— and I refer you to our paper, we’ve got a beautiful model of this— the important thing about contractions for the mother and the baby is the break in between. So we have this intense sensation, we have actually the uterine muscle squeezing. And as the muscle squeezes, you know, that muscle, uterine muscle, is working the same as any muscle. It’s contracting and relaxing. And if you go for a run, you know your muscles contract and relax, and after a while they get sore, right? They get sore because the contractions of the muscle squeeze the blood supply. So for some period of time, blood isn’t flowing in there to supply oxygen, to supply fuel, to take away the waste.
And you know, like a long run, you get sore muscles because lactic acid builds up. Lactic acid is a byproduct of what we call anaerobic metabolism. There’s not enough oxygen getting into the muscle. And what happens in labor as well, we’ve been discovering, is that if the contractions are too strong and too close together, the uterine muscle goes into a form of anaerobic metabolism. When we get lactic acid buildup and the lactic acid buildup makes it more painful, but also in the end, it can actually slow contractions down, you know? So for the mother, you know, the lack of an adequate break, the lack of the ability to replenish between contractions for a uterine muscle is significant, and it’s also very significant for the baby because the baby also relies on that gap between contractions to replenish.
I mean for the baby, you know, as in all placental mammals, there’s only one way out physiologically— which is through the vagina, which is due to the contraction of the uterus. But every time the uterus contracts, it squeezes not only the baby, but it squeezes the placenta, you know, the baby’s lifeline. And as it squeezes the placenta, the blood flow through the placenta, which is what nourishes the baby, gets cut off to some extent, gets reduced or cut off for some period of time. And then, the uterus relaxes, everything’s restored, the blood flow’s restored, the baby gets the blood flow replenished. So, you know, naturally in the placental mammalian birth, for the baby, it’s a… you know, it’s hypoxia, low oxygen levels, and then replenishment, hypoxia, then replenishment.
And mammalian babies are well adapted to this. We’ve been doing it for 65 million years, right? So, you know, we’ve got a whole lot of systems that protect the mammalian baby, and particularly the brain from the hypoxia, the inevitable low oxygen levels in labor. But it’s all designed to work on physiology where there is this adequate time for replenishment.
So the problem with synthetic oxytocin for the baby is the relative time of contraction versus relaxation is changed. There’s more time spent in contraction, less time spent in relaxation and replenishment. And that is a risk for the baby. And we know it’s a risk for the baby because a woman that’s getting administered synthetic oxytocin has to be monitored. Yeah. Because we’ve got to know, is this too much hypoxia for the baby?
And for some babies it is… you know, some babies can’t cope with those extra strength of contraction and the reduced time for replenishment, and some of those babies go into distress and they need to be born quickly or to be born by cesarean.
We know that that’s true for women who have synthetic oxytocin— there’s more cesareans for fetal distress. So that’s the risk for the baby and you know, is that harmful to the baby in the long run? We don’t really know, you know. Is that extra hypoxic stress in labor… most babies can cope with it and it seemed to be okay at birth, but is there… are there any effects, more subtle effects that might be happening from that as well? Questions that we haven’t really answered.
Adriana: And yeah, because as you were saying, like we know that the baby does have some redundancies in place to experience this oxygen sort of deprivation that usually we tend to see, again, as the baby is coming out… like I can think of the expected deceleration of head compressions that even I tell my clients (my doula clients) that the energy in the room will shift because the nurse is then really focused on listening to the baby in between every contraction to make sure are these normal decels expected and just part of the process, or are these things are not going so great? But what you’re saying is that those redundancies and that capacity to tolerate that sort of oxygen deprivation, has a limit to what it can do, and if it’s for an extended period of time, which is what can be caused with the synthetic oxytocin, then the baby starts not being able to tolerate it.
Sarah: For some babies, that’s true. It depends on the baby, and we don’t really know before labor starts, which is why we have to monitor every baby with synthetic oxytocin.
But I also wanna, just go back a point, which is to say this: The stress of being born, we could call it, the stress of this intermittent hypoxia is actually necessary for the baby. It’s not an unnecessary stress. It’s actually a good stress. It switches on a whole lot of systems for the baby, and in particular, it actually triggers for the baby a surge of what’s been called the “catecholamine” hormones. So this catecholamine surge comes from the stress of the hypoxia, comes from actually the pressure on the baby’s head as well.
And the baby gets an outpouring of adrenaline and noradrenaline. The baby gets such high levels that would cause a stroke in an adult, right? But the baby can tolerate it and it’s actually good for the baby. It’s waking the baby up. It’s actually working to prepare the baby for life outside the womb. It’s actually part of the baby’s safety mechanism that protects the brain from the low oxygen levels. It also protects the metabolism from low oxygen levels. It triggers anaerobic glycolysis, the breakdown of glucose even under low oxygen conditions. And it also begins to prepare the baby’s lungs for life. Outside the wo, it opens up the airways, it reduces the lung fluid, increases lungs, surfactant, which is the lung lubricant.
So all of these, this actually intermittent hypoxia. The processes of labor for the baby are actually really important, part of the stress of being born. And if we go to the other end of the spectrum, which is babies that don’t have any labor, so the baby’s born by a pre-labor cesarean, some of the problems that they have are really because they didn’t have labor. So they tend to have a low blood glucose because the catecholamine surge actually helps the baby to get ready for life outside the womb. It gets the baby’s glucose and fuel stores activated free fatty acids, glucose. It also actually helps the baby to begin to produce their own heat because in the womb, the mother’s keeping the baby warm, obviously. But outside the womb, the baby has to produce its own heat. So the breathing, preparation, the preparation to make their own heat, the metabolic fuel activation. Those things don’t happen for a pre-labor cesarean baby. So they tend to be hyperglycemic, they tend to be cold, and they’re more likely than a baby born vaginally to have difficulty breathing after the birth.
Adriana: So it’s just a perfectly calibrated system made to work, right?
Sarah: Yeah, exactly.
Adriana: Sarah, in your research, what have you seen in terms of, we talked about the effects of synthetic oxytocin. What about the effects of other interventions like epidurals?
Sarah: Yeah, so I’ve talked about epidurals in my hormonal physiology report, and we are doing the same systematic review for epidurals working on it at the moment, which is looking at all the studies on mothers and, and babies where they’ve measured oxytocin levels in women with and without epidurals. And the studies do show that there’s a drop in oxytocin for the mother.
And to understand that we’ve gotta go back to our feedback loop that we talked about, our positive feedback loop. And by the way, you can go to my website and go to my blogs and look at my epidural blog and this little picture of this feedback loop if it’s easier to follow.
So the feedback loop, this positive feedback loop that helps to trigger the snowball of labor is dependent on the sensations from the mother’s cervix, vagina, up to the the brain. That information coming up, and that’s what tells the brain to release oxytocin. And the trouble with epidurals is they’re so effective at reducing sensation, at relieving pain, and they actually stop that branch of the feedback loop. So what happens is oxytocin levels go down, or in some cases, in some studies, they just level out, you know, they don’t go up— the snowball doesn’t get any bigger, because the feedback loop has been slowed down or even stopped.
And if we think about the other consequences of that feedback loop, it’s not just increasing oxytocin in the body and driving this snowball of labor, it’s also increasing oxytocin levels in the brain.
So it’s given that calming, connecting, pain relieving activation of pleasure and reward centers as well. So women who have an epidural don’t get all of those benefits as well. There’s a couple of studies we’ve reviewed that have looked at that, and one, for example, looked at, what we call “personality changes.”
So when women go through physiological labor and birth, and we think it’s due to the oxytocin peaks in the brain, they not only get switching on pleasure and reward centers, but they also get a change in personality. And if you think about what we need to mother, you know, we do need to be slightly different or different from what we were beforehand.
So the changes in personality that women get, they become more sociable, they become more relaxed, they describe less physical tension in their bodies. And again, these are all kind of oxytocin effects as well. So in these studies, when women had had an epidural, they didn’t get those personality changes. And the explanation that we would have for that is they didn’t get those peaks of oxytocin in the brain during labor that triggered those changes in personality, that triggered that activation of pleasure and reward centers, calming, connecting, pain relieving effects either.
And you probably are aware, you may be aware that when women have an epidural, they’re less likely to be able to push their baby out. There’s a disadvantage there. They’re more likely to need forceps or a vacuum extraction. And again, that’s our positive feedback loop that’s been slowed down or even stopped. They’re not getting that hormonal help, extra oxytocin to have an effective and efficient pushing stage.
Adriana: So then if somebody’s had a labor that required or had these interventions for whatever reason, what I’m hearing is that it can affect the bonding. So if that’s the situation, is there a way to kind of reset these or reconnect these opportunities or this bonding?
Sarah: Yes. Well, I’ve gotta say, first up, we don’t really have research that’s looked at bonding with epidurals, or not high-quality research. There are some older studies that did find some, we could say changes. Example, in one study at one month, women who’d had an epidural described their babies as less adaptable, more intense, and more bothersome.
And it really, for me, that would be consistent with that they didn’t have that full activation of the pleasure and reward centers at the time of birth and that first date ever, that best first impression wasn’t triggered, and then that comes into the rest of the mothering. So I… and I also wanna say that I’m not saying that if you have an epidural or a cesarean as well, that you can’t bond with your baby. But I think this Mother Nature’s best help, best possible start, there’s a hormonal gap there. So the hormonal gap, as I said, is an oxytocin gap, and probably other hormones as well.
And I just wanna say something else about that because you know what happens is it’s not just the processes of labor and birth that’s missed. It’s all of the lead up, all of the changes that happen in the lead up to labor that make birth as effective and efficient as possible. And one example, we talked about oxytocin receptors and the receptor is what oxytocin binds to like putting a key into a lock and just like oxytocin levels can go up and down, receptor numbers can go up and down.
And if we want an effective and efficient labor and birth, we want a high number of receptors ’cause we want the mother’s uterus to be as sensitive as possible to oxytocin. And that’s actually what happens! People have done studies and measured oxytocin receptor density in the uterus from non-pregnant through to early-, mid-, late-pregnancy and labor, and the number of oxytocin receptors, or the density, goes up from about one and a half to three and a half thousand. So there’s this massive increase in sensitivity, we could say responsiveness to oxytocin in the mother’s uterus.
So then what happens at the onset of labor and birth? The mother releases oxytocin, but she actually doesn’t need very much, she doesn’t need very high levels of oxytocin because her uterus is so sensitive. So it’s not just labor and birth, it’s all these background preparations.
I describe it a bit like a royal wedding, you know? There’s been all these preparations for the exact moment that the spontaneous or physiological onset of labor. And if we induce women, for example, before they’re fully ready, before their baby’s ready it’s like everyone turning up at Westminster Cathedral a week beforehand and expecting everything to be the same. All those final preparations won’t be done!
So the full number, in terms of oxytocin receptors, the woman, by definition, is not gonna have the full sensitivity/responsiveness to oxytocin when she’s being induced. So, it’s… basically, we could call it a window of opportunity. The processes of labor and birth are a window of opportunity for all these things to happen, and if we miss that window of opportunity, for example, through a pre-labor cesarean, maybe even through an induction, it’s gonna take a lot longer to fill in that hormonal gap.
So filling in a hormonal gap, and we’re talking about epidurals to start with, you know, means filling in that brain deficit in oxytocin and in sheep studies actually, the way they fill that hormonal gap was actually injected oxytocin into the brain. But obviously we’re not gonna do that, but we want to have a maximum number of opportunities to release oxytocin, and we do that when we’re skin to skin with our babies. And we do that when our babies suckle, with the letdown or milk ejection reflex. So we release oxytocin.
So skin-to-skin and breastfeeding are the two things that will fill in the hormonal gaps. But we can’t just do it one-off. We can’t even do it for an hour. Actually, if we wanna fill in that hormonal gap, it’s gonna take a lot of patience.
For example, in that personality study that I talked about where women who’d had an epidural didn’t get those changes in personality that women get after physiological labor and birth. Those women breastfed when they breastfed, exclusively for four to six months they got those changes in personality. So it takes a lot longer when you miss that window of opportunity. The window of those peaks of oxytocin on top of all the preparations that have happened.
And same for a pre-labor cesarean. We haven’t talked about that much, but obviously you miss all of the preparations and then you miss the in-labor processes. And the other thing that can happen after a cesarean is it can be hard to get the mothers and babies back together. There’s so much paperwork, and as I said, sometimes the babies have problems. They’re cold, they’re hyperglycemic, their blood sugar’s low, they have breathing difficulties and they get separated.
So for a pre-labor cesarean as well, skin-to-skin contact as soon as possible. You know that it is possible in some circumstances and some institutions to do a cesarean where the baby gets put on the mother’s body straight away and never gets taken off— you know, that’s the ideal.
And then opportunities to suckle as well. For the baby, the baby’s missed all those preparations, the baby’s missed the catecholamine surge that wakes the baby up on every level. So babies born by a pre-labor cesarean are often a bit sleepy. They’re not quite ready. It’s like I say, it’s like someone coming into your bedroom at night and pulling back the covers and shining a bright light on you and pulling you out of bed— you know, you’re not quite ready for it, you know?
So the pre-labor cesarean baby needs that patience as well to fill in those hormonal gaps. And I’ll share another anecdote about this, which is a story I read in a magazine of a woman who’d had two natural births. The third one, she needed a pre-labor cesarean. These interventions could be life-saving in some situations!
And she said, “When I got my baby back, my baby felt different.” And she’s kind of explaining everything that I just explained about the catecholamine surge. And she said, my instinct was to have my baby skin-to-skin. And after three days of skin-to-skin, my baby felt the same. So she could have had an hour and a half of labor. The baby would be the same, but because she missed that window of opportunity, also caught an early sensitive period, she had to be a lot more patient. Yeah. And three days of skin-to-skin filled in that hormonal gap for her and her baby.
Adriana: So fascinating! Is there anything else you wanted to make sure we talked about before we ended?
Sarah: Yeah, just one more thing, which is an important finding from our synthetic oxytocin paper. So, when I wrote my report, and I know there’s a lot of talk out there about synthetic oxytocin and the baby, you know, and some animal studies, raising concerns that when we get synthetic oxytocin labor, it crosses the placenta and crosses into the baby and could have long-term effects on the baby. Some people have suggested that it could make the baby at risk of autism, for example.
Well, the reassuring thing that we found in our study was that the newborn oxytocin levels are already a bit higher— they’re higher than the mother, probably because the process of labor and birth, the stress, the massage-like movements, the skin, stimulation the baby gets through the contractions and trigger oxytocin for the baby as well.
And we also didn’t find any evidence that the baby’s oxytocin levels were higher when the mothers had received synthetic oxytocin. And we also took the trouble of going back to the animal studies and we did some dose calculations. What dose did the animals get? How much did they weigh? How does that apply to mothers and babies?
And we really found that the dosages, the infusion rates that women receive in labor of synthetic oxytocin are just not high enough to cross the placenta to get into the baby, to cross the baby’s brain. That is almost impossible. And also the levels really aren’t high enough to cross into the mother’s brain and have biologically significant effects. So that was a reassuring finding from our report about synthetic oxytocin.
Adriana: Well, thank you so much. Sarah for being here today and for sharing all your expertise. and best of luck with the PhD!
Sarah: Thanks so much, Adriana! And just I just want to end by saying that, you know, our bodies are superbly designed for growing babies, having babies, mothering our babies, and all we have to do really is tune into this Mother Nature, superb design and in labor. You know, how private, safe and unobserved can you make your laboring situation? Can you have a doula? Can you have your own midwife?
Model of care is really the one thing that’s gonna make the biggest difference to your experience of labor and birth. And that’s gonna make a difference to your first meeting with your baby and really set the scene for, you know, a positive, best possible start in life.
So… and if that doesn’t happen, if that’s not possible, there are ways to fill in the hormonal gaps. So, wishing you all, all the very best.
That was family physician Dr. Sarah Buckley who has been writing and lecturing to childbirth professionals and parents since 1997. She is also the author of the internationally best-selling book Gentle Birth, Gentle Mothering. If you go to sarahbuckley.com you can find links to free full versions of most of her research there and you can also read her blog. And if you prefer to connect via social media you can find Dr. Buckley on Facebook at Dr Sarah Buckley.
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And then come back for more ways to inform your intuition.
Lozada, Adriana, host. “Helping Your Mammalian Body (and Baby!) Have an Easier and More Connected Birth.” Birthful, Birthful, April 26, 2023. Birthful.com.
About Dr. Sarah Buckley
Dr. Sarah Buckley is trained as a general practitioner (GP, or family physician) with qualifications in GP-Obstetrics. She has been writing and lecturing to childbirth professionals and parents since 1997 and is the author of the internationally best-selling book Gentle Birth, Gentle Mothering.
Sarah has a special interest in the hormones of physiological labor and birth and the impacts of interventions. In 2015, she completed an extensive report on this topic, Hormonal Physiology of Childbearing, published with Childbirth Connection (U.S.).
She is currently a PhD candidate at the University of Queensland, researching oxytocin in labor and birth and the impacts of perinatal care interventions. She has co-authored several papers on oxytocin in labor, birth, and lactation.
Sarah is also the mother of four adult children, all born at home. She lives in the semi-rural outskirts of Brisbane, Australia.
For more about Sarah and her work, see her website, where you can find her blog and full links to much of her research.
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