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What Causes Labour To Start?

Pregnancy is a long process, but it all comes down to one important final event: labour. It’s one many women spend months and even years of their lives wondering about, anticipating, and potentially even dreading. The experience is like no other - a total mystery until you do it for the first time. In fact, even science can’t tell you so much about the mysteries of labour. Like why does it happen when it does? What causes it?

In this article, we break down the how and why of labour.

What Happens Before Labour

While you may be looking at your due date, 40 weeks after your date of conception, as something concrete, it really amounts to little more than an educated guess. In reality, term labour can last for between 37 and 42 weeks. In fact, nearly a third of women don’t even give birth within ten days of their expected due date. Even crazier, only five percent of babies are born on their actual due date.

So what exactly goes on in your body in those last few weeks that determines when the baby will finally emerge? Here are just a few signs your body is getting ready for labour.

First, weeks or days before your delivery, you’ll probably start having something called Braxton Hicks contractions. These aren’t the real contractions that push out the baby during labour. Instead, they help your body prepare for the real thing. It’s basically just your uterus tightening and contracting and is usually considered painless, though some women mistake it for true contractions. That’s why they’re often nicknamed “false labour.” The main difference is that Braxton Hicks contractions don’t actually change the shape of your cervix.

Speaking of your cervix, it also experiences some changes right before labour in preparation to let a baby through. Namely, it’ll get thinner and softer. It may also expel something called a show, which is a mucus plug. It’ll look like a pinkish blood-stained, well, ball of mucus. It’s not pretty, but then again, neither is pregnancy.

Other first signs of labour include cramping, loosening of joints, and having diarrhoea, as your rectum is one of the pelvic muscles that loosens pre-labour. Many women also report the phenomenon of nesting, or the desire to clean and organize in preparation for their baby’s arrival.

One other, slightly more pleasant, body change you can expect before labour is something called lightening, which is when you suddenly have more room to breathe before labour. This happens because your baby engages, or shifts further down your pelvis so that its head is facing toward your cervix in preparation to come out of the birth canal.

Signs That Labour is Starting

While all of the above early signs of labour can occur days and even weeks before you give birth, there are other symptoms hours before labour that are more useful as signs that labour has started. One of the best-known ones is when your “water breaks,” which usually happens no more than 24 hours before you go into labour.

So what’s actually happening when your water breaks? Well, when your baby develops inside your womb, it lives in a bag of fluid, your amniotic sac. When your baby is ready to emerge, that sac will break, and all of the fluid will have no place to go other than to come out of your vagina. But it’s not always the dramatic event you see in movies. Sure, it may come out in a big rush, but it also may just trickle. And there’s a chance it won’t even happen at all and that your baby will be born still in the amniotic sac. That’s why you can’t rely on your water breaking as the only surefire sign that you’re going into labour.

The only true symptoms of going into labour are the ones that are used to define the beginning of labour: having contractions. This is when your body works to open up your cervix so that your baby can come out. This happens when your uterus presses down on your baby, whose head then presses down on your cervix. This, and the release of the hormone oxytocin, will trigger contractions.

Contractions will probably feel like physical discomfort, dull ache, and pressure in your pelvis, back, and lower abdomen. A lot of women compare them to strong period cramps. Toward the beginning of labour, they’ll start out as weaker, shorter, and farther apart from one another. As you get closer to giving birth, they’ll become longer, stronger, and more frequent.

The Stages of Labour

The phase when your cervix dilates from zero to six centimetres is called early labour and it can last for quite a long time, as long as hours or even days. During early labour, your contractions will be mild and irregular at first and then progressively become more intense and frequent. Even though you may want to head to the hospital immediately, many doctors recommend staying at home during early labour, where you’ll be more comfortable and are less likely to need medical intervention.

After your cervix expands to six centimetres, you’ll reach what is called active labour, when your cervix dilates from six to ten centimetres. During this stage, your contractions will come every three to four minutes, will last around 60 seconds each, and will feel much more intense and uncomfortable, to the point that it’ll be difficult not to focus on them. At this stage, you’ll want to head to your birthing place, whether that be the hospital or just a prepared birthing area in your home. Active labour will generally last between four to eight hours.

Together, these two phases make up stage 1 of labour. Stage 2 of labour will be when you actually deliver your baby, which includes all of that pushing you hear so much about. This can take anywhere from a few minutes up to a few hours, though you can expect it to take longer if you’re giving birth for the first time.

Unfortunately, that’s not the end of labour. In stage 3, you’ll deliver the placenta, which can take anywhere from five minutes to an hour. You’ll continue to have contractions and will need to push again in order to get the placenta out. After that, your uterus will immediately continue to contract in order to get back to its normal size. It’ll take up to six weeks for this process to be completely finished.

Learn more: Postpartum - A survival guide for the fourth semester.

Hormones and Labour

Just like with every part of pregnancy, there are a lot of hormones at play in the labour process. First up: oxytocin, which is often known as the cuddle hormone, as it is released when people snuggle up or bond. Oxytocin also plays a role in labour, as it triggers contractions (and also the letdown of your breast milk).

All of the loosening of your cervix, joints, and bowels that comes along with labour is caused by the hormone relaxin, which does exactly what it sounds like. Another hormone, prostaglandin, also helps to open up your cervix, as well as allows your body to be more receptive to oxytocin.

One hormone you’re likely to be very grateful for is beta-endorphins, a type of endorphin that not only helps with pain relief, but also creates feelings of joy and euphoria. Beta-endorphins also slightly suppress your immune system so that it doesn’t overreact to the “foreign object” that is your baby.

Finally, your body will also release epinephrine and norepinephrine, also called adrenaline and noradrenaline, which you might know as the fight-or-flight hormones. Typically associated with stress, a rise in epinephrine increases your levels of prostaglandin and cortisol, which stimulate contractions and help give you the energy to push during stage 2 of labour.

Learn more: Pregnancy Hormones – Why can’t I keep it together?

What Causes Labour

All of this useful information aside, you may still be wondering… what causes labour after all, especially if you’ve reached your due date, are tired of waiting, and want to induce, or artificially trigger, labour.

Well, the potentially disappointing truth is that the precise cause of labour is one of the many medical mysteries that scientists still don’t have a real answer to. The best we can do is share a few theories that scientists are considering for possible causes of labour.

Researchers have found that there is something that tends to be present in a greater quantity in the amniotic fluid as a woman starts labour: telomeres. These are a part of our DNA that responds to ageing, and could potentially work to signal to a foetus that it’s time to be born. The idea is that this a way for an unborn baby to essentially tell its mother that it wants to come out.

Another theory has to do with fetal lung development. At around 32 weeks of pregnancy, your baby’s developing lungs start to produce something called surfactant protein, (SP-A), which helps your baby breathe once it leaves your uterus. During late pregnancy, SP-A activates immune cells that are busy clearing the uterus of viruses and bacteria. Those immune cells, also called macrophages, make their way over to the uterus wall where they stimulate an inflammatory response that is thought to begin the process of labour.

Inducing Labour

Now, all of this science-y talk is all well and good, but you can’t exactly inject yourself with surfactant proteins if you want to induce labour. So what can you do?

Interestingly, about 25% of all labours in the United Kingdom are induced, most often because the mothers are considered overdue to give birth, usually at around 42 weeks. Doctors will choose to induce labour in order to reduce risk to both mother and baby, as there is a higher chance of stillbirth and other complications if you go over 42 weeks pregnant.

In the hospital, inducing labour is done by applying a topical form of the hormone prostaglandin to the cervix. If this isn’t an option because of reasons such as the mother having had prior uterine surgery, a doctor may choose to open the cervix mechanically with a catheter or graduated dilators insead.

To encourage a woman’s water to break, a practitioner might swipe their finger along the membranes that connect the amniotic sac, which triggers the uterus to release prostaglandin, softening the cervix and causing contractions. If this doesn’t work, the doctor may even manually rupture the amniotic sac.

If, after a few hours, none of these steps brings on regular contractions, doctors will typically administer Pitocin, a synthetic form of the hormone oxytocin, intravenously. This is usually successful at triggering contractions within half an hour, and these contractions are stronger, more regular, and more frequent than those that occur with natural labour.

Inducing Labour at Home

Of course, there are often situations in which women want to move things along on their own and induce labour at home before a doctor may agree to do it in a hospital. For that reason, there are many different methods that are commonly used to bring on labour. However, you should know that these don’t have any sort of scientific evidence, ultimately amounting to little more than old wives’ tales. However, if the anecdotal evidence is to be believed, some of these methods are very effective. Here are just a few.

- Moving around: Taking a walk or going up and down the stairs is thought to encourage labour by helping your baby drop further down into your uterus.

- Having sex: Between stimulating the uterus, triggering the release of oxytocin, and introducing high-in-prostaglandin semen into your body, there are many reasons why having sex is often recommended as a way to naturally induce labour.

- Eating something spicy: Because digesting them can trigger the release of prostaglandins, eating hot foods is commonly cited as a way to encourage labour to begin.

- Castor oil: Due to its loosening effects (it’s often used as a laxative), castor oil is often used as a way to induce contractions. Just beware that this method tastes pretty gross and isn’t considered the safest option. You’ll definitely want to talk to your doctor before you try it.

Ultimately, whether you induce your own labour at home, are induced at the doctor, or simply let nature takes its course, we hope this article has been able to help you understand what you can expect when your due date comes - whenever that may be.

If you have more questions around childbirth, pregnancy, or postpartum care, visit our free consultancy platform - Ask Lola&Lykke Experts.

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