Hormones of Labour

If you plan on or have ever attended an Antenatal or birth class then you are bound to have learnt about the hormones of labour. To be well informed and really know what to expect of labour and birth, a general understanding of the hormones involved is essential. It can feel a bit technical but by knowing a little about the ins and outs of some of our body’s hormones, you can properly prepare for labour, understanding what is happening in order to help you work with your body towards a positive birth experience.

Decisions you make about the care you receive can either help or hinder how these hormones work so it’s important to understand how they work, why they are important and how they may be disrupted so that you can make informed decisions.

Basically… both the mother and the baby’s body’s make birth hormones which if left undisturbed, work together to ensure labour and birth progress smoothly. These hormones have a number of roles:

- Preparing your body to give birth

- Starting labour

- Preparing the baby for labour and extrauterine life

- Preparing the mothers breasts to feed baby

- Building a bond and love between mother and baby

So today we will cover the four main hormones of labour: Oxytocin, endorphins, adrenaline and prolactin

Oxytocin – aka the hormone of love. It’s the hormone that is released with orgasm, in heated kisses or when you’ve had that warm rush of heat up your body after watching your kids do something beautiful and you just feel so in love with them. It’s also responsible for contractions in labour as well as milk ejection ‘letdown’ when breastfeeding.

As your pregnancy progresses, oxytocin receptors increase preparing your body for labour. Oxytocin is what causes the uterus to contract which thins out and dilates the cervix, pushes the baby lower and out of the birth canal to be born. Levels of oxytocin increase gradually in labour and peak just after birth. As the baby is pushed onto the mother’s cervix and pelvic floor, stretch receptors trigger a further increase in oxytocin levels which then strengthens and encourages more contractions. With the highest level of oxytocin occurring at birth, often women feel a sense of alertness and elation as their baby is born, which is sometimes referred to as a post-birth high.

Oxytocin is also present in the baby at birth and remains elevated for the babies first 4 or 5 days which helps mum and baby bond and get to know each other. Oxytocin is responsible for the let-down reflex in breastfeeding. So baby is born, hopefully is brought onto mum’s bare chest at birth for skin to skin time and to initiate a first breastfeed.

Then on top of contracting the uterus to expel the baby, oxytocin also continues to work on the uterus once baby is out in order to deliver the placenta. With high oxytocin levels, strong contractions lead to separation of the placenta from the internal wall of the uterus and then assist in clamping the uterus together to stop the bleeding (like putting pressure on an open wound).

If oxytocin levels are low during labour, contractions may slow or stop, which means labour can take longer and often leads to health care providers recommending interventions. Reasons why oxytocin levels may be hindered include an epidural as sensations of stretching as the baby is being born are altered and therefore the regular increase in oxytocin is disrupted. Oxytocin can also be hindered by the release of stress hormones adrenaline and noradrenaline which ill flesh out in a bit…

I guess if you can picture this idea that oxytocin levels are high with orgasm – try and imagine a couple trying to make a baby in a hospital room with bright lights on, people watching and telling them they’ve got a time limit. Of course no one in this situation is feeling high levels of oxytocin and so no ones going to be orgasming in this scenario. But this is exactly how we set up for birth – we have women in white bright rooms with machinery around, and strangers watching, telling them what to do and how long they have to do it – so of course oxytocin levels struggle. I’ve said it before in other episodes, but wherever you plan to give birth – create an environment that is calm, comfortable, relaxing and TBH could be somewhere you’d have sex – because you want to encourage as much oxytocin release as possible to help this labour and birth progress as smoothly as you can.

Some ways that you can help increase the production of oxytocin in your body during labour and birth include:

- staying calm and comfortable and not feeling stressed (in order to avoid the release of the stress hormones),

- create an environment that promotes oxytocin and have people in your environment that you trust and feel safe with

- staying upright in labour so that the pressure of the baby on the cervix and pelvic floor can increase production of oxytocin

- nipple stimulation in labour and then skin to skin and breastfeeding if baby is born and you need assistance in delivering the placenta as sucking at the breast increases oxytocin levels.

Beta Endorphin – aka the body’s natural pain killer.

During times of pain or stress the brain releases beta endorphin to help calm and relieve pain. Levels of endorphins are often higher at the end of pregnancy and during an unmedicated labour levels of endorphins continue to rise. It is the hormone that helps women have what Dr Sarah Buckley calls the ‘on another planet’ feeling or an altered state of consciousness during an unmedicated labour.

High levels can cause a reduction in oxytocin which can slow the labour but this can be seen to be a positive natural way to help the mother cope with the pain – you see a woman start becoming overwhelmed as the pain increases and then somehow she continues to cope for another hour or two before that pain becomes too much and then again, somehow she gets past that and keeps pulling through – this is where a release of endorphins has kicked in. You may have heard women or midwives even talk about how intense an induction of labour is and part of this is because if a woman has the synthetic oxytocin inducing her contractions, she misses out of this natural endorphin hit that comes with an unmedicated labour. Also, when pain medications like morphine or an epidural are introduced during labour, levels of endorphins greatly decrease.

Following the birth, beta-endorphins assist in the bonding that occurs between the baby and mother (as the baby will also have high levels of endorphins from the birth process). High levels of endorphins in labour also stimulated the release of prolactin which prepares the mother to breastfeed once bub is born. It is also passed to the baby in breastmilk which explains baby’s milk drunk, natural high following a breastfeed.

It is thought that a drop in endorphins in the days following the birth contributes to the baby blues.

Adrenaline (epinephrine) & Noradrenaline (norepinephrine) (known as catecholamines) – aka fight or flight hormones.

These survival hormones are activated by feelings of danger or fear and can slow contractions or stop labour altogether. Like animals in the wild, our bodies are made to give birth when feeling safe and if there is any concern for safety, naturally the body will postpone labour and seek safety. You can see this clearly where some women have experienced slowing of contractions or contractions completely stopping when they move from labouring at home to the hospital – again that analogy about being in a safe and comfortable environment

These fight or flight hormones can also be released in response to hunger. So it is really important to eat (especially in early labour) to gain energy for the long slog of labour that can go on for hours.

Too much adrenaline can also put the baby in distress as blood flow to the uterus, the placenta and therefore the baby is reduced which can lead care providers to recommend interventions like Caesarean section.

One positive affect that these fight or flight hormones have is during the second stage of labour. Often the woman finds her contractions may stop and she can rest for a short period before a sudden peak in these fight or flight hormones in combination with high oxytocin levels helps to quickly birth the baby by what’s known as the fetal ejection reflex. In thinking about the example of the animal in the wild, at this stage this fight or flight response is to speed up the birth so the mother can gather up the newborn and get to safety.

To keep these fight of flight hormones at bay during that first stage of labour there are a number of things that women can try including:

- staying calm and comfortable – like I’ve already touched on - create an environment where you feel safe

- Being informed means you can be prepared for conversations that may arise, and can help you feel like you have some control over what is happening

- Having a trusting relationship with your care provider who knows and supports your wishes – a lot of research shows the benefits of Continuity of Midwifery Care models in doing this

- Avoiding disruptive or intrusive procedures

Catecholamines can drop quickly after birth causing a woman to get shaky and feel cold. Often a warm blanket is wrapped around the woman to ensure oxytocin levels remain elevated which is needed to prevent excessive bleeding.

Prolactin – aka the mothering hormone & is best known for its role in breastfeeding.

Prolactin levels in the blood increase throughout pregnancy which stimulates the growth & development of breast tissue preparing the breasts for milk production. During pregnancy high levels of estrogen and progesterone prevent secretion of milk from the breasts but the steep decline in these pregnancy hormones post birth means the milk secretion is no longer blocked. As a baby sucks at the breast prolactin levels increase which stimulates milk production and therefore the more a baby sucks at the breast the more milk will be produced. This is particularly important in establishing lactation and a good milk supply so letting bub feed as much as bub wants over the first 6 weeks will be really beneficial.

Research has also shown that prolactin levels are higher at night so those night BFs that you may dread, are particularly important for keeping up your milk supply.

Prolactin is also known to affect the mothers brain, inducing maternal behaviours, reducing stress and when combined with high levels of oxytocin (which is seen either just after birth or with breastfeeding), is believed to stimulate a mothers satisfaction and selfless devotion to her baby.

For the baby itself, prolactin plays an important role whilst the baby is still inside in development and maturation of the fetal lungs. And once born, is essential for newborn growth & development and helps the baby adjust to life outside the womb.

Ways to promote high levels of prolactin include staying calm and relaxed, keeping baby and mum together from birth and try to initiate early breastfeeding and continue responding to your newborn by breastfeeding on demand. Avoiding mixed feeding, supplementing and use of a dummy if possible whilst establishing lactation (first 6 weeks) so that your breasts get as much stimulation as possible. Avoid contraceptives that have estrogen as this can cause a decrease in milk production. Smoking is also known to decrease prolactin levels.

So, they are the four main hormones of labour that you will hear about if you’re going to antenatal or birth classes or reading books about labour and birth. I think they’re really interesting but also important to understand so that mothers can trust what their bodies are doing, and how labour works. It helps us see how complex labour and birth is and how important these hormones are in achieving an optimal birth & postnatal experience.

You’ll have picked up from episode 12 where I discuss some pain relief options for labour, and also through some of what I’ve touched on today that these hormones can be disrupted by the introduction of medications and interventions. I thought I’d just quickly flesh out some of the effects intervention can have on inhibiting the way the hormones of labour play out…

- Syntocinon during labour does not cross the ‘blood brain barrier’ meaning that it doesn’t reach the brain. Which means it isn’t working as the hormone of love – it will have its physical effect on the uterus – making it contract, but it doesn’t bring with it all the euphoric, loved up emotions that come with natural oxytocin. And unfortunately, there is a negative feedback to the brain from the body’s oxytocin receptors which signal the brain to reduce its natural production of oxytocin. Synthetic oxytocin is also shown to prevent that much needed increase in endorphins that unmedicated labours and births experience as I mentioned earlier.

- Opiate painkillers like Morphine but also fentanyl and other drugs used in epidurals come with risks to both mother and baby which I explain in ep12. But the use of these drugs, like oxytocin will inhibit the woman’s own production of her natural pain killer endorphins. As I also mentioned earlier an epidural will inhibit the fetal ejection reflex as the stretch receptors on the mother’s pelvic floor are numbed and the burst in adrenaline that is needed in second stage doesn’t happen. This means the effort of pushing out the baby may be greater – which may explain why women who have an epidural statistically have an increased length of second stage and are more likely to need assistance with the birth by instrumental delivery.

- Caesarean section – this would depend on whether it’s an elective caesarean with no labour or an emergency following a labour… If no labour has occurred research shows significantly lower levels of all four of these hormones in mothers which can make you question what effect this would have on the mother/baby relationship and initial postnatal period. For babies as well, if they’ve missed out on the process of labour, they have missed out on the catecholamine surge which puts them at a greater risk of respiratory compromise and low blood sugar levels. Depending on the type of CS and the hospital that it happens in sometimes babies and mums will be separated at birth and the initiation of skin to skin and breastfeeding can often be set back a few hours which as I’ve touched on can affect the production of prolactin and also oxytocin which are essential in mother baby bonding and breastfeeding.

Obviously, Caesareans are often needed to save lives so we can’t get too upset by some of the potential disruptions that happen if a CS is needed. However, being aware and choosing pathways or models of care that support an undisturbed birth as much as you can have control over, can be so beneficial. Not everyone can have or even wants to have an unmedicated/undisturbed birth, but if this is something that you are hoping to achieve, I thought I’d quickly share some tips to point you in the right direction…

Model of care – choose one that encourages and supports an undisturbed birth – a model of care or a health care professional that believes that women can give birth, trusts women’s bodies, and really supports your wishes. There’s a lot of research that points to midwifery continuity of care models as the way to go here so check out what options you have in your area.

When choosing who you’ll have as your labour and birth support, have people who again, trust that you can do it without medication and intervention. Whether that’s a doula or it’s a friend or mum who can be that support along with your partner, make sure you build a team that wants what you want. It’s no good having your anxious mum there questioning your ability or suggesting pain relief when they see you’re in pain, if that’s not what you want.

I’ve said it before and I’ll keep saying it – create a birth and labour environment that feels safe, warm, comfortable, where you feel unobserved and free to do whatever your instincts tell you to do

If you can avoid it – don’t use any pain relief measures that will alter or inhibit the natural release and working together of these incredible hormones

And following prioritise mum and baby being together from the moment the baby is born. Have skin to skin from birth and initiate breastfeeding within the baby’s first hour of life.

For those of you who may have had a medicated birth or birth with interventions obviously you can have incredible birth experiences, can feel an absolute joy and bond with your baby at birth and can still have wonderful breastfeeding experiences so this isn’t to say you’ve missed out. And for people heading towards labour and birth I think being educated and informed is so important and can be so helpful in having a positive birth experience, however we also need to remember that it’s not just us as the mum in this birth process and so things can go down a path that you hadn’t planned or hoped for and that’s okay. Try to go into birth informed, prepared but also flexible.

Okay, I hope that wasn’t too much information and that it all made sense. I understand it can be hard being just audio and not visual content so if you need to save this episode and re-listen closer to your due date, do that! Because as I always say – being educated and informed is so helpful in equipping you to make confident decisions – whether that’s around birth or parenting…

If you’re keen to read up on this topic more here are some great resources:

Dr Sarah Buckley – Pain in Labour: Your hormones are your helpers, 2020

Childbirth Connection - The Role of Hormones in Childbirth

Infant and Young Child Feeding - The Physiological basis of breastfeeding, 2009

Yoga Baby – Hormones of Labour & Birth by Dr Sarah Buckley

Photo by @kalinorton