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The Hormones of Labor and Birth (and Why You Should Care)

Hormones are an essential part of normal labor and birth. In this blog post you’ll learn about the nine hormones of labor and birth and why they matter for you.

mom calm and happy right after birth in water

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I’m guessing you’ve heard about the princess that could feel a pea under her 20 mattresses. It seems silly that she could feel something that small. But something else pea-sized affects all of us day-to-day. It’s called the pituitary gland.

The pituitary gland produces and secretes hormones. Hormones manage and affect almost every function of your body. 

And for women, hormones are at their highest levels during pregnancy, labor, and birth.

(To be sure I’m not misleading anyone, let me be clear: the pituitary gland does produce hormones. But during pregnancy many hormones are actually produced by the placenta instead of the pituitary gland.)

Why Should I Care About Hormones?

Hormones are like little chemical messengers in our body. They come from our brain and travel through our bloodstream, managing basically every system and function in our bodies.

Hormones affect things like growth and reproduction. They are also connected to common health issues like anxiety, weight gain, and gut health, to name just a few. Those are topics for another day though.

When it comes to labor and birth, hormones matter for one simple reason: they control the entire process.

Inherent in that is the fact that if you mess with the hormones, you mess with the process.

The Dance of Hormones

The interplay of the various hormones involved in labor and birth has been called a dance. It’s a delicate process with certain steps that need to occur, and it can be thrown off easily.

Delicate and precise, the physiology of hormones in mother and baby is beautiful. It’s all designed to work together synergistically to provide ideal outcomes for baby and mom.

When medications and other medical interventions are introduced into that dance, the steps get all messed up. And usually, one intervention will lead to another and another, further compounding the problem.

That common downward cycle is called the cascade of interventions, which you can learn about in The Cascade of Interventions [Explained].

The Hormones of Labor and Birth

For as long as women have been giving birth, they’ve needed hormones to direct labor so it could proceed safely and effectively. That was essential for the continuation of the human race, especially a world of past years that had very little medical knowledge and no emergency rooms.

After birth, women needed hormones to kick in to help them fill two basic human needs of their children – nourishment and protection, which in this case take the form of breastfeeding and attachment.

We now live in a world that has hospitals, formula, and other alternative solutions that women of the past didn’t have. But hormones are still an indispensable part of the process of labor and birth.

But what are these hormones we’re talking about? What are they called and what functions do they have? Wonder no more.

Here are the 9 hormones of labor and birth that you need to know about and why each one matters for your birth experience. 

1. Oxytocin

If you only read one section of this article, read this one. Oxytocin is basically running the show. It plays a role in preparing your body (and your baby) for labor, helps contractions happen efficiently, and contributes to recovery and bonding after birth.

Oxytocin Prepares Your Body for Labor

Let’s start at the beginning. Oxytocin does two main things to help get you ready for labor. 

Before I explain those things, though, you need to understand that in those last couple weeks of pregnancy, your uterus and your baby develop hormone receptors. These receptors are like a lock that hormones fit into like a key. They open the door and make it possible for oxytocin to bond to the uterus (and the baby) and do its job.

Once enough oxytocin has bonded to those receptors, contractions start and labor begins. That is the first way oxytocin gets you ready for labor. 

Note: If labor is induced by Pitocin (synthetic oxytocin) before those receptors have developed, it is likely that the induction will fail because your uterus simply can’t utilize the Pitocin or contract appropriately. 

The second way oxytocin helps prepare your body for labor is its role in “ripening” the cervix. In order for a baby to be born, a mother’s cervix (the small passageway that connects her uterus and her vagina) has to soften enough that it can thin out and open up.

Oxytocin Helps Labor Progress Efficiently

Once labor has begun, natural oxytocin, produced by your body, controls contractions. These natural contractions are perfectly orchestrated to be strong enough to help labor progress but not so strong that it’s too much for you or your baby to handle.

Natural contractions have breaks in between and feel like waves – with a gradual start, a peak, and a release.

Oxytocin vs Pitocin + an Epidural

Many women are induced or receive Pitocin at some point during labor. Contractions started by Pitocin, though, are stronger and longer and closer together than natural contractions and can get out of hand if not managed closely.

I’ve heard it said that Pitocin contractions feel more abrupt and, therefore, harder to handle, not like a wave you can feel coming on that has a peak and a natural easing at the end.

Because it makes labor more painful, Pitocin often leads to an epidural. This is problematic because of how it interferes with oxytocin in a woman’s body.

Oxytocin creates its own positive feedback cycle which encourages labor to progress normally. But that cycle is interrupted when an epidural is administered.

When a woman is numbed by an epidural, she is no longer feeling labor sensations. If she isn’t feeling anything, her body doesn’t know to keep producing the hormones needed to help the process continue normally. And once those hormones stop, labor slows or stops altogether. 

More Pitocin can be given to replace her oxytocin that has shut off and labor can continue, but now labor is being controlled by a machine and a medication, not your body, and that has its own dangers.

Oxytocin Aids in Recovery and Bonding

After labor is over, oxytocin still has a role to play. While you hold your new baby, oxytocin is telling your uterus to continue contracting. This has two purposes: 1) to expel the placenta and 2) to help your uterus begin to shrink. 

This is when one dangerous side effect of using Pitocin during labor might show up.

Remember those hormone receptors your uterus develops? They can be overwhelmed by artificially high amounts of Pitocin. And when they get overwhelmed, they stop working well.

If they stop working well, the message from the oxytocin (or Pitocin, which is sometimes given again after birth) to keep contracting isn’t received and your uterus doesn’t shrink. If your uterus doesn’t shrink, you bleed more.

And that’s when postpartum hemorrhaging happens.

In those same moments when your uterus is supposed to be expelling the placenta and shrinking, you, hopefully, have your baby on your abdomen and you’re beginning to initiate breastfeeding.

Breastfeeding stimulates the production of oxytocin, further increasing the ability of your uterus to shrink down. (That’s why breastfeeding is one of the original cures for postpartum hemorrhaging.)

That oxytocin released while breastfeeding has another purpose, even after the contractions stop. Oxytocin is the hormone of bonding. It helps you develop your maternal instinct and your love for your new baby. It also aids in creating a secure attachment for your child.

As a final benefit, oxytocin may help in preventing postpartum depression. Though studies are somewhat inconclusive, generally, higher levels of natural oxytocin are linked to lower rates of postpartum depression.

2. Beta-endorphins

Beta-endorphins are one of about 20 different types of endorphins that exist in our bodies. They’re the ones we usually think about when we refer to endorphins (like when we’re talking about how exercising helps us feel good). 

“Endorphin” is a combination of two words: “endogenous,” meaning internal, and “morphine,” which you probably know is the name of an opioid, the strongest class of pain-relievers we have. Why do we call this hormone “internal morphine”? Because that’s exactly what it is.

We humans literally produce an opioid-level painkiller inside of us in response to stress and pain. It produces an overall good, happy feeling, reduces stress, and changes the way our brain perceives pain.

So the assumption that women who give birth unmedicated are doing nothing to alleviate the pain is actually incorrect. We have methods of pain management too – they’re just internal!

RELATED >> How to Cope With Contractions: Natural Pain Relief During Labor

3. Prostaglandins

If we’re being technical, prostaglandins actually aren’t hormones. But they are hormone-like, so we’re going to talk about them anyway.

Prostaglandins are produced by your body wherever they are needed, unlike most hormones which are produced in the hypothalamus in your brain and released into the bloodstream. In non-pregnant people, they work to control inflammation, blood flow, and blood clotting.

In pregnant women, prostaglandins are one of the main elements that start spontaneous labor. Working with oxytocin, prostaglandins soften your cervix so it can begin to dilate. This happens naturally when your body and baby are ready for labor to begin.

If a doctor were to induce you, prostaglandins (in gel or pill form) would likely be used vaginally to help ripen your cervix. Prostaglandins are also the reason some people say that sex can trigger labor because semen contains high amounts of prostaglandins.

4. Catecholamines

Catecholamines (cat-uh-coal-uh-means) is the fancy word for the hormones epinephrine (which is often called adrenaline) and norepinephrine. Epinephrine and norepinephrine fuel our natural fight-or-flight response.

These two hormones play lots of important roles in labor and in making sure your baby is healthy when he or she is born.

At the end of labor, mom naturally gets a surge of catecholamines (remember, that’s adrenaline) that gives her a final boost of energy to push her baby out.

This same surge benefits the baby too. Without it, the baby is more likely to develop labor hypoxia, which means he or she doesn’t have enough oxygen, and is more likely to have breathing problems after birth. 

Catecholamines also play a role in heat regulation for the baby immediately postpartum. They stimulate use of oxygen, fatty acids, and sugars, all of which help to produce and regulate heat.

When the baby is born by c-section, both mother and baby miss out on this surge of hormones.

Induction can also mess with the catecholamines because the baby’s systems, including the endocrine (i.e. hormone) system, aren’t fully developed and won’t function as they would in a full-term baby.

When Helpful Ends and Hurtful Begins

Like I said, adrenaline and norepinephrine are our “fight or flight” hormones. This fight-or-flight response can be helpful when we’re in dangerous or stressful situations. In labor, it’s very not helpful.

While a healthy surge of these catecholamines at the end of labor helps the baby arrive safely, too much of these hormones in the beginning or middle of labor can slow or stop contractions.

We were designed to have that natural fight-or-flight response; it’s a good thing. But a laboring woman shouldn’t have to worry about her safety. 

Unfortunately, that can be hard – on a psychological level – in a world where birth often happens in hospitals.

In a hospital, surroundings are unfamiliar, strangers are coming in and out of your room, bright lights are shining on you, machines are beeping, and you’re receiving cervical checks every few hours.

That kind of situation could stress anyone out. It is far more likely to cause stress to a tired mother who has already been laboring for hours.

Beyond that, whether at the hospital or anywhere else, if a woman in labor is isolated or left without familiar, continuous support, it is likely that she will feel unsafe. And feeling unsafe will trigger that fight-or-flight response and labor will begin to slow.

5. Prolactin

Prolactin levels are low in men and in non-breastfeeding women. In lactating women, prolactin levels are very high. That’s why prolactin is often called the breastfeeding hormone. 

Prolactin aids in breast development throughout pregnancy and stimulates milk production after giving birth. Together with oxytocin, prolactin promotes bonding between mother and baby. 

Beta-endorphins also work together with oxytocin and prolactin, all stimulating release of the others, to achieve a successful vaginal birth.

Prolactin levels actually decrease during labor and then, like catecholamines, spike before birth. Because of this, getting a c-section may mean that mom and baby miss out on elevated levels of prolactin. That may be part of the reason mother and baby pairs who experience a c-section are less likely to breastfeed

It has also been suggested that natural peaks in prolactin (and cortisol, which we’ll talk about next), combined with early and frequent breastfeeding promotes development of prolactin receptors, which may aid in ongoing milk production.

6. Cortisol

Cortisol is often thought of as a stress hormone, but it’s not all bad. Like catecholamines, if too elevated, cortisol can cause labor to slow or stop. But in appropriate amounts, cortisol has many functions during late pregnancy, labor, and birth.

Cortisol may play a role in helping a baby’s organs finish developing.

Healthy levels of cortisol can also promote contractions, increase the effectiveness of oxytocin on bonding and attachment, and help to improve a mother’s mood postpartum.

7. Relaxin

Relaxin is a hormone you’ve probably heard about if you’ve been exercising throughout pregnancy. This is the hormone that makes your joints and muscles a little looser.

It’s important in preparation for birth because it helps your pelvis be more flexible as your baby navigates his or her way through.

Relaxin levels rise quickly during labor which continues to prepare your pelvis and also helps your cervix soften and dilate.

8. Estrogen

Fun fact: there’s actually three kinds of estrogen. E2 is the one found in women during their childbearing years – it’s the most common and the most potent. E1 is found in women after menopause. E3, called estriol, is the type found in pregnant women. 

If you know your pregnancy hormones, you know that progesterone dominates during pregnancy. But estrogen – in this case, estriol – also plays a role.

During pregnancy, estriol helps regulate other hormones, helps baby’s organs develop properly, and helps grow and direct the functioning of the placenta.

Estriol helps your uterus grow as your baby does and helps your uterus be more efficient during labor.

9. Progesterone

Progesterone does a lot of things during your menstrual cycle and during pregnancy. When it comes to birth, progesterone has one main role: preventing it from happening too early. 

Progesterone and prolactin counteract each other. If progesterone is high, it keeps prolactin low. This is what you want during pregnancy – you don’t want to be producing milk yet and you don’t want labor to start too soon.

If prolactin is high, it keeps progesterone low. This is what you want at the end of pregnancy – for labor to be able to begin and for your body to start producing milk.

Note: Some women can get pregnant while breastfeeding. In that case, prolactin and progesterone can coexist without causing problems.

Now You Know

If you’re still reading, I’m proud of you for taking the time to learn about something most women know very little about. Clearly, you want the best for yourself and your baby and you’re putting in the work to get there.

Hopefully you understand now why hormones are so important to labor and birth. They are integral to a safe, effective labor and birth. 

With that knowledge, I hope you also have a clearer idea of why a woman would choose to labor and give birth unmedicated. There are so many positives to avoiding medications and interventions when they aren’t medically necessary!

So just remember, even though labor might feel a little chaotic and very intense, what’s happening internally is a delicate dance. 

The fewer things you do to interrupt that dance, the higher your chances are of a calm, happy birth experience. And that’s what I want for you — a birth day that you look back on with pleasant memories and gratitude!

I promise that’s possible!

Until next time,

Allison

Sources: 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4720867/

https://www.yourhormones.info/topical-issues/hormones-of-pregnancy-and-labour

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