What happens to a woman's body as she gives birth?
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What happens to a woman's body as she gives birth?

Every labour is different – but there are certain, sometimes surprising, experiences a woman can expect when giving birth. What are they?

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Birth is often described as a "miracle" and in many ways, of course, it is. There’s the fact a baby can go from living in a tiny, protected bubble to independently taking its first breath; there’s the sheer power of nature and the extraordinary strength of women and their bodies.

"Even after 20 years, I am still blown away every single time I see a baby born," says Dr Vicki Woodward, an obstetrician from Melbourne’s Royal Women’s Hospital. "I still cry at births."

In other ways, birth is not that miraculous: it's a primal and imperative act without which we wouldn’t exist.

A human is born in Australia every minute and 44 seconds, the Australian Bureau of Statistics estimates. Globally, about 250 babies are born each minute.

No two labours are quite the same, but there are certain processes that can be expected as a woman’s body arranges and rearranges itself, in sometimes surprising ways, to give birth. "When women understand what’s happening in the body, even though it’s uncomfortable … it’s reframing it as a positive," says Hilary Rorison, an adviser from the Australian College of Midwives. "It’s your body actually working hard to do something, it’s not pain for the sake of pain."

So what does happen to a woman’s body during birth? Why is it often a good sign if a woman yells at people during labour? And what difference can various interventions make along the way?

Credit:Illustration: Dionne Gain

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What are the first signs a woman is going into labour?

The suddenness of labour is something scientists have not been able to fully explain, but research suggests it is the fetus that releases physical and hormonal signals to initiate birth.

"There is a complex interplay that we don’t truly understand," Woodward says. "If we really knew exactly what triggered birth, we would use that method when inducing." (More on "inducing" later.)

The first stage of labour, called the latent phase, can begin hours, days or even weeks before the actual birth. Common experiences include irregular contractions, "practice" contractions called Braxton Hicks, lower back or period-like pain, a vaginal passing of blood-stained mucus, or the baby dropping lower in the pelvis. This phase also often includes the waters breaking, when the amniotic sac in which the baby is ensconced ruptures.

Woodward says women might have diarrhoea too. "To get a baby out of your pelvis, all your ligaments and everything has to relax and stretch and make room for the baby to move through. So it relaxes all your other muscles, including those of the bowel wall."

But she says the most important change is that the cervix – the neck of the womb – starts to move forward and soften, with the help of a hormone called relaxin. "[The cervix] starts by being about two to three centimetres thick and then, miraculously, over the course of that first part of the labour it becomes paper thin – and then it will really start to open up."

It can be hard to tell when labour is truly kicking off. Every mother has her own story. Aedin Treloar has two sons – Cullen, three, and Oisin, seven months – and was not sure if her waters had broken when she went to hospital the first time (they had, a bit).

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Carly Clark was surprised, despite being in pain, to discover her cervix was already more than halfway open when she arrived at hospital both times she gave birth, to daughters Mackenzie, in 2017, and Andie-Rose in 2019.

"I had a fear I would turn up and they’d say, 'You’re nowhere near ready to give birth,' " she says.

Credit:Illustration: Dionne Gain

Contractions – why?

A contraction is when the muscles of the uterus tighten – which is when women feel pain – then relax. "I think [what] surprises women so much is how hard their tummy goes," Woodward says. Each contraction works to push the baby down and to open the cervix so the child can pass through.

Clark describes contractions as "like the extremity of severe period pain", worsening as labour progresses. "It would be like a rubber band constricting inside you as tight as it can," she says. "There’s not a lot of reprieve."

Treloar likens the pain to a "screwdriver" sticking into you.

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The culprit is another hormone, oxytocin – more commonly known as the "love hormone" because it is involved with bonding and breastfeeding –stimulating the uterus to contract.

Another hormone, prostaglandin, also helps to open the cervix and makes the body more receptive to oxytocin. And the body makes its own pain relievers in the form of beta-endorphins.

"If you ask a woman if she felt like she had pain relief and it was a natural birth, she’d probably say no – but when you’re talking to them, it’s like they’re on another planet," Rorison says.

Meanwhile, the "Ferguson reflex" is doing its work: the baby drops into the pelvis and pushes against the cervix, prompting the body to release oxytocin. This then drives contractions and pushes the baby’s head further into the cervix, causing more powerful contractions, in "a positive feedback loop".

It’s important to minimise a woman’s stress, Rorison adds, as the stress hormone cortisol can make labour more painful or slow.

How do you know when to go to hospital?

"A good active labour is really strong, regular contractions that are making your toes curl," Woodward says. "They’re relentless and they roll on through."

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In the "active" phase, there are usually between two and four contractions that each last from 45 seconds to a minute, in a 10-minute block. Imagine feeling an extreme cramp for the time it takes to do a couple of dozen push-ups or to floss your teeth – over and over again, for hours. The cervix tends to dilate about one centimetre for every one to two hours of regular contractions, usually faster if someone has given birth before.

It’s at this point that a woman will often be instructed to go to hospital – 96 per cent of births in Australia occur in hospitals, according to the Australian Institute of Health and Welfare (AIHW).

This phase of labour ends once the cervix is dilated by 10 centimetres. "[This] stage is absolutely the longest. For women having their first baby, they can be in active labour – where you’re truly contracting regularly – for eight to 10 hours, and it might be four to six hours for second babies," Woodward says.

How is a labour induced? What is a “stretch and sweep”?

About a third of Australian births in 2018 were induced – initiated by medical intervention. Often it’s because a woman is overdue, Woodward says, but it can also occur due to health complications or for social reasons. "Our aim when doing an induction is to try to mimic normal birth as much as possible," Woodward says.

But how do you hasten a baby’s arrival?

In a "stretch and sweep", a clinician runs their fingers around the cervix with the aim of triggering a release of hormones that will set off labour.

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Or, if the cervix is thin and open enough, the clinician inserts a small, hook-like tool to break a woman’s waters if they haven’t already broken. "Sometimes that’s just enough to get things going," Rorison says. "That’s more common with people having subsequent babies."

If the cervix isn’t yet open, a balloon catheter can be inserted to create pressure and encourage it to open.

Synthetic versions of hormones oxytocin and prostaglandin can also be administered, by drip and by gel or pessary, respectively, to help prime the cervix and nudge the uterus to start contracting.

But the main difference between an induced labour and a natural one is that it can be more painful. Woodward says it’s not entirely clear why: it could be that a woman who is being induced was always going to have a slightly more difficult labour anyway, or that being induced doesn’t allow the body enough time to "warm up". Research also suggests synthetic hormones don’t cross into the mother’s brain and so don’t offer the same coping effects.

Credit:Illustration: Dionne Gain

When is getting grumpy a good sign?

A woman moves to the second stage of labour via a "transition" phase, which tends to last about half an hour. "It comes with an awful feeling of, I just can’t do this any more," Woodward says, "and they get quite restless and angry and grumpy … you’ll often see obstetricians and midwives looking at each other with sort of slight smiles on their face because we know they’re doing really well."

(This response can be blunted when a woman has had an epidural; see below.)

"When the movies show women yelling at people, that’s the kind of classic transitional behaviour. And it’s a real signal to everyone around … the baby is nearly here.

"Once we start pushing with the contractions, it feels very different to just having to suffer through them."

'It’s a bit like you’ve run a marathon and now I’m going to ask you to sprint the last kilometre. It’s very, very unfair.'

The urge to push is triggered when the baby’s head fills the pelvis and presses on the bladder and bowel. Rorison explains: "It stimulates the same nerve as when you have to do a poo. So it’s just this overwhelming urge to push."

Woodward says this part can be extremely difficult for mothers.

"It’s really, really hard work. It’s a bit like you’ve run a marathon and now I’m going to ask you to sprint the last kilometre. It’s very, very unfair."

A baby’s head is usually about 9.5 centimetres in diameter, she explains, but because the birth process takes time, the mother’s vaginal tissues can gradually stretch. "How much stretch the tissues have in them is sort of dependent on your genetics."

Pushing often takes between 60 and 90 minutes for a first baby and anywhere from two or three pushes to half-an-hour for subsequent births.

"The uterus has fabulous muscle memory … It contracts much stronger and more efficiently with the second baby," Woodward says. "But also because mum’s done it before, it enables them to know how to push really well."

Monica Dux, mother of two and author of Things I Didn’t Expect (When I Was Expecting), says birth classes had her picturing her vagina as "an opening flower" and she wasn’t prepared for just how primal labour would feel.

"It was most obvious in the sounds I made. I can’t replicate that moaning. You go into a different part of yourself," says Dux.

"It really struck me that something happened to me that was like nothing else I’d ever experienced."

Without an epidural, the baby coming out feels like a lot of "stretching and stinging" and the head crowning, or emerging, is often described as "a ring of fire", says Woodward.

"The classic everyone talks about is it’s like giving birth to a watermelon."

Three-quarters of women having a vaginal birth experience either a tear or a pre-emptive surgical cut to minimise tearing, called an episiotomy, AIHW data shows.

But, of course, as Clark recalls, "All I could think about at that point in time is, I’m about to meet this little baby I’ve carried for nine months inside me."

Woodward says contractions often become further apart in the last 20 minutes as the head comes out, giving the woman a chance to catch her breath. "I think it’s nature’s really clever way of slowing things down to help ease the pressure of the baby on the perineum [the area between the vulva and anus].

"Then, after the shoulders are out, the baby tends to slither on out."

Does pain management change the process?

Ball squeezing, foot stamping and using a bath or shower are all methods of dealing with labour pain. Machines that involve attaching electrodes to a woman’s back to send electrical current to her body, called TENS machines, are also popular as are “hypnobirthing” and “calm birthing”, where women practise particular mantras, breathing techniques or meditation.

But what if a woman wants more?

Inhaling nitrous oxide gas will take the edge off the pain, Woodward says, and this won’t get to the baby. Some women opt to pair this with a morphine injection, which can cross the placenta. It is safe but can slow a newborn’s first breath if given too close to the birth, so is used with caution.

While those two measures don’t really change the process of a natural birth, Woodward says, an epidural can – injecting anaesthetic into a woman’s back to make her numb from the chest down. Epidurals don’t generally reach the baby but they can lead to a longer labour. It can be harder to push, and there is a slightly increased risk of the use of forceps – like “tongs” that can help to gently pull out the baby by its head – or a vacuum device that acts as a suction cup on the baby’s head. But Woodward adds that most epidurals these days are patient-controlled with a button, so women can administer less when they reach the pushing stage.

Rorison says an epidural can be “absolutely brilliant”.

“If a woman has a baby that’s in the wrong position … and she’s getting an early urge to push, or if she’s really tired and has been labouring for a while and [her cervix is] not dilating, for some women they have that epidural and their whole body relaxes and they go on to have their baby,” she says.

Rorison adds that epidurals do interfere with some labour hormones, leading to a drop in maternal oxytocin, probably because the mother’s sensory feedback is numbed.

What happens during a caesarean section?

Two-thirds of Australian births are vaginal and a third are done by caesarean section, where baby and placenta are removed from the womb via an incision close to the pubic hair line (avoiding the abdominal muscles).

An elective caesarean is planned for reasons such as having had a C-section previously (almost three-quarters of vaginal births after a caesarean are successful, Woodward says, but there is a one-in-500 chance of the scar rupturing, which can be dangerous for mother and baby); or a breech presentation, where the baby’s bottom is down and head is up, which is thought to be less safe for the baby; or, sometimes, it is simply the mother's choice.

An emergency caesarean usually occurs because a labour isn’t progressing or the baby has become stuck.

But at the end of any C-section, the same hormonal triggers that occur when a placenta is delivered vaginally (more on this below) will also occur, Woodward says, and more hospitals are advocating for women to have immediate skin contact with their baby while surgery on their abdomen continues, because of its role in promoting bonding and breastfeeding.

Woodward adds that babies born by elective C-section may have different gut microbiomes because they don’t pick up the good bacteria in the birth canal, but this is not thought to be harmful.

Some label it the 'easy option' or use the phrase 'too posh to push' while idealising a drug-free, vaginal birth.

C-section is major abdominal surgery, so you’re off heavy lifting and driving for up to a month, but Woodward says recovery from vaginal birth can be difficult too. "Some people have an easy, nice, elective C-section and feel fine the next day while someone will have a complicated vaginal birth and feel rotten."

Treloar had two C-sections: one planned and the other because her labour was not progressing after almost 11 hours on synthetic oxytocin to induce. Both births were "beautiful", she says, and she is baffled by the stigma still surrounding C-section; some label it the "easy option" or use the phrase "too posh to push" while idealising a drug-free, vaginal birth.

"We behave like it’s the worst thing that could happen to you," Treloar says. "What’s so wrong with a C-section?"

Credit:Illustration: Dionne Gain

So the baby is out. What’s next?

While babies practise breathing in the womb, their lungs are still filled with water when they are born. They take their first breath of air once their head and chest are out of the vagina, typically within the first minute.

"The first breath is initiated by a few factors," says Rorison. "One is the cold air on its face, another is the sudden decompression of the chest following birth."

Shaking and slapping babies to prompt breathing is no longer the done thing. "But we may tickle their toes or ask the mother to blow gently on their face. That usually does the trick," Woodward says.

A baby’s first breath stimulates its body to absorb all fluid from its lungs, so the lungs can take over the job of oxygenating blood from the placenta, an organ that provides oxygen and nutrients to the fetus during pregnancy.

This period is dubbed 'golden hour' and the baby is usually very alert, eyes wide open and really paying attention.

Newborns are usually placed on their mother’s tummy or chest. The uterus pauses and the skin-on-skin time triggers a spike in oxytocin.

"We try to not interrupt that, there are really awesome things going on in terms of the mum and baby bonding," Rorison says.

Rorison says this period is dubbed "golden hour" and the baby is usually very alert, eyes wide open and really paying attention. It’s also often when babies first crawl to their mother’s breast to feed. The initial form of milk, called colostrum, is produced before or immediately following birth.

"But many babies in the first hour or so will mouth around and not suck deeply at the breast. This is normal. The important thing is to allow them to be close to you," Woodward says. "If they feed, great. If they don’t and they just want to smell you and taste you and cuddle, also great."

Clark describes this moment as one of total elation, joy and relief. "When they place that little body on your chest, it’s complete and utter love."

Treloar agrees: "It’s so, so amazing … I couldn’t have imagined anything different."

How do they know when to cut the umbilical cord?

The umbilical cord, which carries blood between the baby and the placenta, is usually clamped about five minutes after birth, Woodward says. These few minutes give the newborn a little time to get extra nutrients from the placenta as it adjusts to life out in the world.

Rorison says: "We like to 'wait for white' – as in, wait for the umbilical cord to have no blood left in it … I've had some babies where the cord is white at five minutes, others at 15."

Once clamped, the baby is no longer attached to the placenta and the cord can be cut.

'I tell partners, when they cut the cord … it’s a bit like cutting tough calamari.'

The cord – about half a metre long and two centimetres thick – has one big vein and two smaller arteries surrounded by thick connective tissue called Wharton’s jelly.

"I tell partners, when they cut the cord, that it’s tougher than they expect. It’s a bit like cutting tough calamari," Woodward says.

A plastic clamp, which looks like a clothes peg, stays on what’s left of the cord attached to the baby’s belly button. This remainder then dries up and falls off after about a week.

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But wait – there’s more?

The burst of oxytocin from the skin-on-skin contact between mother and child helps the uterus to contract again so the placenta can come away.

"Women seem surprised by the birth of the placenta. They are so focused on the baby, that often the placenta is forgotten," Rorison says.

Once the placenta separates from the uterine wall, "it just sort of slides on out", Woodward says. Most placentas "deliver" about 10-15 minutes after the baby, but it’s normal for this to take up to about an hour.

This stage is when midwives and doctors are often most nervous.

Rorison says this stage is when "midwives and doctors are often most nervous". It’s why women are often given an injection of synthetic oxytocin just as the baby is born.

The placenta needs to be fully expelled and the uterus then needs to contract down on itself to prevent excessive bleeding from where the placenta had been attached. Post-birth contractions put pressure on the uterine blood vessels to stop them bleeding freely, Rorison says. "It’s about the size of a dinner plate (22 centimetres in diameter, on average) … that’s a dinner plate-sized wound on the uterine wall."

After-birth contractions continue and are usually most painful in the first 48 hours. "It’s the body working to keep you safe but it can be really uncomfortable," Rorison says.

Some women experience postpartum chills, where they feel shaky or cold, which Rorison says may be due to a surge in adrenaline or loss of fluid and heat during birth. It’s usually over within a couple of hours of birth.

Credit:Illustration: Dionne Gain

Why do women get tearful or agitated after giving birth?

"The birth of the placenta allows this mass hormonal flush – it’s one of the biggest hormonal changes a woman will ever experience in her life – and that causes the milk to come in," Rorison says.

Oxytocin, again, and prolactin are the two primary hormones that cause the breasts to engorge and produce milk made up of proteins, fats and other nutrients – and making breast milk is a staged process. It usually increases in volume and becomes transitional breast milk three or four days after the baby is born, Woodward says. It becomes "mature" about two weeks later.

The massive hormonal shift can feel overwhelming. "Lots of women get the baby blues where they’ll spend a day crying," says Woodward. "That’s about 70-80 per cent of women."

Every system in your body, from the gastrointestinal tract to respiratory system, will be recalibrating post-pregnancy.

Clark recalls becoming very emotional. "I realised this little person was going to rely on me for a long time."

Treloar felt severely agitated. "I remember really wanting to leave hospital … I was so close to tears."

When pregnant, a woman’s blood volume rises by about 50 per cent and her heart rate and cardiac output increase to cater to herself, her growing baby and the placenta.

"The other thing that happens during pregnancy is fluid shifts out of the blood vessels and into the peripheral tissues, and that’s why women get puffy legs and ankles and fingers," Woodward says. "And [as soon as the baby’s out] all that fluid starts to come back into the blood vessels and your heart rate changes. So it’s quite incredible."

In fact, every system in your body, from the gastrointestinal tract to respiratory system, will be recalibrating post-pregnancy.

Woodward says women don’t generally notice too many of these post-birth changes, aside from perhaps fewer heart palpitations or shortness of breath. There is also evidence of an increase in endorphins, which Rorison says give women "a bit of a high" for a couple of days after the birth.

How does birth change a woman’s body long-term?

One-hundred years ago, 70 babies died for every 1000 born. In 2018, the number was three. There are very few maternal deaths – 27 occurred on the day of birth between 2008 and 2017 that were directly related to pregnancy or labour.

But tragic complications do occur, as does birth trauma, with some women experiencing lasting impacts.

Most common is damage to the pelvic floor muscles, Woodward says, which run between the pubic and tail bone supporting the bladder, uterus and bowel. "It gets damaged in labour even when it’s a perfectly lovely, normal labour," she says. "That’s why pelvic floor exercises [before and after birth] are super, super important."

Post-birth issues can include reduced sexual satisfaction, severe perineal tearing, prolapse (where pelvic organs herniate into the vagina) and urinary, faecal or wind incontinence. Roughly one in seven women experiences postnatal depression in the weeks after her baby is born. Some mothers develop postpartum post-traumatic stress disorder.

She would never quite return to her old body … but she points out that all bodies change, regardless, as they age.

Rorison says regardless of how a woman gives birth, she needs to feel heard, respected, informed and safe for the best chance at positive outcomes.

"A woman can have a birth, on paper, that is a normal vaginal birth, no pain relief but it can feel traumatic for her – or she can have an emergency C-section and feel really happy with that," she says. "It’s all about how we treat women in labour."

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Woodward adds that the body’s recovery after pregnancy and birth can take time. "Literally every single system of the body is changed during pregnancy," she says. "It’s a miracle that within six to eight weeks after birth a lot of those have gone back to normal."

Dux hadn’t anticipated that she would never quite return to her old body – she says she sometimes pees when she jogs, and her stomach carries stretch marks and excess skin – but she points out that all bodies change, regardless, as they age.

"You do change quite profoundly, not in a bad way, but as a culture we don’t give women space to have that," Dux says. "What our bodies do to make a baby is really, really hard work … and it’s amazing we do that."

And while many changes may sound unnerving, Woodward points out there is one positive change that tends to outweigh the negatives: "The baby and that lovely relationship you have for the rest of your life."

Credit:Illustration: Dionne Gain

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