What Actually Happens to Your Body During Pregnancy?
Pregnancy is often described as a time when your body “changes”.
That's putting it mildly.
Over roughly 40 weeks, your cardiovascular system, respiratory system, metabolism, hormones, muscles, joints and nervous system all adapt to support a growing baby.
And some of those changes can be surprisingly relevant to the aches, pains and stiffness you may experience along the way.
So, what's actually happening?
It's not just about the growing bump
The most obvious change during pregnancy is, of course, your growing abdomen.
As the uterus enlarges, your body has to accommodate an increasing amount of weight at the front of your body. Your centre of mass changes, and your trunk and pelvis have to adapt to these new mechanical demands.
Your posture and movement may change as a result.
But it's important not to think of this as your body developing one particular “pregnancy posture”.
There is considerable variation between individuals, and your body is continually adapting throughout pregnancy.
You aren't simply moving into a new position and staying there. Your body is constantly adjusting to the changes taking place.
Then there are the hormones
Pregnancy involves some dramatic hormonal changes.
Oestrogen, progesterone, relaxin and other hormones all change throughout pregnancy and have effects throughout the body.
These hormones aren't simply preparing you for labour. They influence the cardiovascular system, metabolism, reproductive system and connective tissues, among many other things.
And this is where some of the common explanations for pregnancy-related aches and pains become a little too simplistic.
Relaxin: the hormone everyone talks about
Relaxin is probably the hormone you're most likely to hear about when people talk about pregnancy and joints.
It has important roles during pregnancy, including effects on connective tissue and the changes involved in preparing the body for childbirth. Relaxin can influence collagen metabolism and the mechanical properties of connective tissues.
This has led to the common explanation that relaxin simply “loosens your ligaments”.
There's some truth behind this, but it's an oversimplification.
It doesn't mean that all of your ligaments suddenly become loose or that your joints become unstable.
And it certainly doesn't mean that every pregnancy-related back or pelvic pain is caused by a pelvis that has become “loose”.
Pregnancy-related musculoskeletal pain is much more complicated than that.
Your pelvis doesn't simply “come apart”
The pelvis has to accommodate significant changes during pregnancy and childbirth, so it's understandable that pelvic stability can become a concern.
The joints of the pelvis do undergo changes during pregnancy, but this is part of a much broader adaptation of the musculoskeletal system.
Importantly, pain and joint movement aren't the same thing.
You can have pelvic pain without having an obvious increase in joint movement, and increased movement doesn't automatically mean that a joint is painful.
This is one reason why describing pregnancy-related pelvic pain simply as your pelvis being “out of alignment” or “unstable” isn't particularly helpful.
Your muscles have a new job too
As your body changes, your muscles have to adapt to different loads and positions.
The abdominal wall stretches as the uterus expands. The pelvic floor supports increasing loads. The muscles around your spine and pelvis work within a changing mechanical environment.
Meanwhile, you're carrying more weight and often moving differently.
This doesn't necessarily mean your muscles are becoming weak because you're pregnant.
Their job is changing.
This is one reason staying appropriately active during pregnancy can be helpful when medically appropriate. Exercise gives your muscles an opportunity to maintain strength and physical capacity while your body adapts to its changing demands.
Your centre of gravity is changing
As your baby grows, the distribution of weight through your body changes.
Your nervous system has to continually adapt to this.
Balance can therefore feel different, particularly later in pregnancy.
This doesn't necessarily mean you've suddenly become less coordinated. Your brain is learning to control a body whose size, shape and weight distribution are changing week by week.
It's a remarkable example of how adaptable the human body is.
Why can your back start to ache?
Pregnancy-related low back and pelvic pain is common.
A large systematic review and meta-analysis estimated that around 63% of pregnant women experience lumbopelvic pain, although there was considerable variation between the studies.
There isn't one single explanation for this.
The changing mechanical demands on the spine and pelvis are likely to contribute, but so can changes in muscle function, activity levels, previous pain, sleep and other individual factors.
This is important because it means there isn't one universal exercise or treatment that will work for every pregnant person.
Two people can have very similar pregnancies and completely different experiences of pain.
Why can other parts of your body start hurting?
Pregnancy-related discomfort isn't limited to the lower back and pelvis.
You may notice changes in your:
hips
ribs
upper back
neck and shoulders
wrists and hands
feet
Sometimes the explanation is mechanical - your body is dealing with different loads.
Sometimes it's related to changes in activity, sleep or the positions you're spending more time in.
And sometimes several factors are contributing at once.
For example, sleeping can become more difficult, you may spend longer in certain positions, your daily activities change and you're carrying an increasingly heavy baby.
Your musculoskeletal system has to deal with all of it.
Does pregnancy mean you should stop exercising?
For most people with an uncomplicated pregnancy, no.
Current evidence supports physical activity during pregnancy, with exercise offering benefits for maternal health and helping to maintain physical capacity.
Exercise may also help with pregnancy-related back and pelvic pain, although the evidence varies between different types of exercise and different outcomes.
The important point is that exercise during pregnancy doesn't have to mean following a rigid pregnancy workout programme.
Walking, swimming, strength training, cycling, mobility work and other activities may all be appropriate depending on the individual, their pregnancy and any medical considerations.
As pregnancy progresses, the way you exercise may need to change.
That's adaptation - not failure.
If you are unsure about exercising during pregnancy, particularly if you have a medical or pregnancy-related condition, speak to your midwife or maternity team.
And then the baby arrives...
And the changes don't stop when your baby is born.
After months of adapting to pregnancy, your body suddenly has a completely different set of demands.
Feeding, carrying, lifting and settling a newborn can mean spending a lot of time in positions your body isn't used to - often while you're tired and not getting as much sleep as you'd like.
Your body is also recovering from pregnancy and, depending on your birth, from labour and delivery.
So it's completely understandable if you don't feel like your “old self” straight away.
Recovery isn't a switch that gets turned on after birth. It's another period of adaptation.
If you're interested in what happens to your body after pregnancy and some of the common aches and pains new mums experience, take a look at our blog:
Because looking after yourself isn't an extra job to add to the list.
It's part of looking after your baby too.
When should you get some advice?
Although aches and pains are common during pregnancy, significant or persistent symptoms shouldn't automatically be dismissed as “just pregnancy”.
It may be worth getting advice if pain is:
persistent or getting worse
affecting your sleep or everyday activities
limiting your mobility
stopping you from doing things you want or need to do
causing you significant concern
And it's important to remember that not every pain during pregnancy is musculoskeletal.
If you develop a new, severe or unusual symptom, or anything that concerns you about your pregnancy, contact your midwife, GP or maternity team for appropriate advice.
The Take-Home Message
Pregnancy is much more than a growing bump.
It's a period of profound hormonal, mechanical and physiological adaptation.
Hormones such as relaxin, oestrogen and progesterone influence tissues throughout the body. At the same time, your changing weight distribution, centre of gravity, muscle demands and activity levels require your nervous and musculoskeletal systems to continually adapt.
That can contribute to aches, pains and changes in how your body feels - but it doesn't mean your body is failing.
It's adapting to one of the biggest physical changes it will ever experience.
And perhaps that's a better way of looking at pregnancy-related aches and pains:
not as your body going wrong, but as your body doing an enormous amount of work.
Would you like some help?
If you're pregnant and struggling with back, pelvic, hip or other musculoskeletal pain, you don't necessarily have to put up with it until your baby arrives.
An assessment can help identify what's contributing to your symptoms and whether there are ways to make everyday movement more comfortable.
If you'd like to talk to us about your symptoms or book an appointment, get in touch with the team at Exmoor Osteopathy on 07824 168862, email info@exmoorosteopathy.co.uk, or:
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