Back pain in pregnancy

The third trimester promises that the fulfillment of the joys of pregnancy is imminent. Your little bundle of love is almost ready to arrive on dry land to say “hello world”.  Now, the second trimester brought with it the fun days of nesting, energy, glowing skin (for some) a nice, neat bump to be proud of. Your forte was planning and organising, everything was peachy.  However, with less than three months to go something seems to be going to pot. Yes, I have been there too! As a mom of two, I can totally relate to the tricky third trimester where back pain is prevalent amongst many pregnant women (every second one of us).  

Back pain can be experienced in all stages of pregnancy. Often regarded as a self-limiting problem, many women are left in the dark to scrounge around the internet to find some solutions. It DOES NOT have to be this way. But first, let’s clear up a few important facts about back pain in pregnancy: 

 Not ALL back pain in pregnancy is self-limiting. You should see a doctor immediately if the following occurs: 

  • You’re unable to pass urine 
  • You have a complete loss of bowel or bladder control 
  • Unremitting (day and night) severe back pain 
  • Numbness in the groin, genitals, and bottom 
  • Sudden unexplained weight loss 

The above is not that common (about 2% of pregnancies).  However, NEVER ignore them!  They could be as a result of a concerning condition called Cauda Equina syndrome.  Your spinal cord may be compressed which may result in permanent nerve damage. You should seek a surgical opinion in A&E as a matter of priority. 

So, what causes back pain in pregnancy? 

Back pain is complex and multidimensional, yes even in pregnancy. Our beliefs, lifestyle, habits, diet, health, sleeping, resting, exercise and emotions can influence it.  

The obvious scapegoat is the cocktail of hormones to many an expectant mom in pain. I felt so guilty, when I was sick, in pain, or could not sleep at night because I was meant to be endlessly grateful for the hormones giving my growing baby all the best to expect in Chez Utero.  

What do hormones do for us?

If our brain was the mothership for all human conscious and unconscious processing, our endocrine system would certainly be the first commander for all missions. The entire development of the baby from when they are simply two cells with ½ the DNA each on a mission to unite, divide, thrive, and conquer is controlled by hormones. In the early stages,  

FSH (follicle stimulating hormone) is responsible for the growth of eggs in the ovaries. 

hCG (Human chorionic gonadotrophin) is a hormone produced by the cells that surround the early embryo and can be detected in the urine after as little as 7-9 days after fertilisation.  Over the counter pregnancy tests reveal the presence of this hormone and hence whether you are pregnant. Those cells that produce hCG go on to form the placenta. 


Not only is a female’s sexual development and menstrual cycle, but this hormone is also the wonder hormone that protects bones and joints. Oestrogen not only helps the uterus grow but maintains uterine lining too, but acts as an important, regulator for other hormones. Oestrogen also helps the development of baby’s organs. This powerful hormone also causes pregnant women to have a stuffy nose and causes hyperpigmentation patches on the skin. 


Progesterone helps to regulate the menstrual cycle, and in pregnancy, helps thicken the lining of the uterus. The lining is like a soft cushion ready for a fertilised egg. The ovaries usually produce progesterone but when pregnancy occurs, higher levels are produced by the placenta. Progesterone together with, relaxin are on a common mission to prepare the mom’s anatomy for later pregnancy and eventually labour.  They help soften ligaments and cartilage, and make a mom’s joints more pliable and mobile to allow for the growth of your little one.


I remember when I first read about this hormone as a 4th year Physiotherapy student, I was convinced it was an oversimplified and convenient name for a hormone, (akin to renaming the uterus- the womb). But no, it is indeed the scientific name and relaxin meets the full expectation of what it sounds like. Over each trimester it “relaxes” or softens your ligaments and joints in preparation for labour. However, because the hormone is released into your circulatory system, it does not only affect the pelvis but the entire body, making joints more mobile. It can sometimes cause you to feel unbalanced too. In the third trimester, relaxin also softens widens, and lengthens the cervix.  


Dubbed as the love hormone, oxytocin has been found to be present in higher volumes in people in the early stages of romantic attachment.   The warm fuzzy feelings like trust, security, and contentment are linked to oxytocin too. In pregnancy, it is mostly known for stimulating labour contractions. Once your little baby has been born, it helps mobilise milk into the breasts and also aids with decreasing the size of the uterus.  

 Watch this handy video about what hormones do in pregnancy:


The incredible multiplication of cells is complex, beautiful, genetically predetermined. This astounding process mind-blowing to say the least is so rapid, with profound changes in ligament laxity and an enlargening uterus. Your centre of gravity moves forward, a lot!  So, the lumbar spine and sacroiliac joint have to work harder to withstand these changes and increase in load. Let’s put this in context. According to Yousuf et al. 2011, the angle of the thoracic spine curvature increased by 12% between 12 and 22 weeks and increased by a total of 24% between 12 and 32 weeks.  They also found that the lumbar spine curvature increased by 18% between 12 and 22 weeks and by a total of 41% between 12 and 32 weeks.  The human spine is robust and responsive to change, however, these rapid changes in the spinal curvature can sometimes cause overload, and if the supporting muscles and structures are not robust and strong enough, it will cause a failure of the tissues, and can cause a strain on discs, facet joints and the sacroiliac joint too.  

 Similarly, as the baby grows in size, the abdominal muscles stretch and lose their effectiveness as dynamic stabilisers of the lower back too. Sometimes the muscles can separate (diastasis recti) which can cause an inefficiency in the way your back and sacroiliac joint tolerates load and can cause pain too.

Weight gain

Have you heard the urban legends and old wife’s tales before?  

 “Eat what you want- you’ll lose it when you give birth” 

“The baby will keep you busy and the weight will fall off” 

“Keep eating, the baby gets it all” 


There are others too, some so ridiculous, I cannot even bear to type them!  According to a 2020 study, women with a Gestational weight gain (GWG of ≥15 kg) had a higher prevalence of persistent lower back pain. But why? The reason may not be as simple or obvious. The reality is that our spines are strong, robust, and resilient and can withstand load. We will keep reminding you of this because there are far too many worry mongers out there spreading false information.  In 2014, researchers found that BMI (body mass index) did contribute to back pain but did not necessarily cause structural changes in the spine. However, increases in adipose (fat) tissue may cause metabolic changes that could be responsible for back pain. In patients with a BMI over 30 overexpressed pro-inflammatory cytokines are present. Those increased levels of cytokines are considered to be the link between obesity and inflammation 

Why should you avoid obesity in pregnancy?

Elevated levels of chronic inflammation can cause and detrimentally increase leptin in the body. Leptin is a hormone in the body, secreted by fat cells that helps us regulate our body’s energy. Too much leptin will stop your hypothalamus from knowing when it is full. (The hypothalamus is in the middle of the brain and lets us know when we are full and satisfied by food, or thirsty) The more fat cells that we have the more leptin your body will make. So, too much leptin means not knowing when you are actually full! Therefore, again we can see that maintaining a healthy BMI during pregnancy will help you know when you have eaten the correct amount of food!


Stress and anxiety 

Pregnancy is a life-changing life moment and can come with a rollercoaster of emotions, highs, lows, even the expected. Birth stories, the financial considerations of preparation for your little one, changing family dynamics, the impact on relationships can all set your mind racing. Everybody responds differently to stress, some of us need it to motivate us and some of us suffer negative consequences. A recent study amongst healthcare workers showed that psychological stress increased the incidence of lower back pain. There’s plenty of evidence in good-quality research about the negative effect that stress has on back pain. Pain is complex and has many dimensions and should not be oversimplified. There are so many contributing factors! Perceptions, history, and social factors also play an important part. We call this the biopsychosocial framework. A complex model demonstrates that pain is complex and multi-factorial. I prefer calling it the patient-centered approach. What we need to understand is that pain has many influences and that a variety of psychological and social factors not only affect back pain but also can impact your life, and function.  

Survival of the fittest, does stress really need us to react this way?

Stress, can raise your body’s resting cortisol, stimulate, and exhaust your fight or flight system (sympathetic nervous system) and perpetuate pain. The stress associated with having a baby and the chemicals associated with that can then make it easier for future stresses to bring on pain. It becomes a bit like a trigger such as a piece of music or a fragrance that can remind you of a specific moment in your life. Inevitably over time, this can change the way the body behaves. Eventually, this can actually cause a depletion of serotonin (happy hormones). 



We live in a stressful world, so what?

Stress is a normal part of life. It is not the stress that is bad but our response to that stress. If you have a big increase in stress or something has changed in your life where it’s harder to cope with stress, then stress can increase your sensitivity and can increase your chance of having pain. Not only is stress (and stress tolerance) related to the persistence of pain, it is also related to how we recover. Prominent levels of stress can impair our recovery from physically taxing components of our lives. Sometimes a  stressful or traumatic event can cause us pain. That stress and the chemicals associated with that can then make it easier for future stress to trigger pain.  Has a song or smell ever brought a memory back to your mind? So too can a stressful moment trigger pain.  It does not mean that you are weaker or have injured or re-injured yourself! All it means is that you have a heightened sensitivity  and it’s easier for normal life stressors to trigger a pain response. 

Lack of sleep 

Sleep is protective. It helps us to both heal recover. A powerful desensitizer, often more potent than medicines. It builds our tolerance to all the things that can sensitize us. Lack of sleep (less than 7 hours for some) or interrupted sleep can sensitize you. So, perhaps your pain should be 1/10 but consistently missing sleep amplifies that pain to 4/10. . Lower levels of sleep have been linked with both increases in injury (e.g stress factors in athletes or the military) and increases in pain related to changes in the nervous system’s sensitivity. In his book “Why we sleep” by Matthew Walker, shares  two of his sleep studies- one online and the other in a sleep lab. Walker shows how sleep deprivation and poor quality sleep affect the brain and how we perceive pain.

Does a lack of sleep make you feel grumpy?

Walker found that there was increased activity in the pain centres of the brain (the somatosensory cortex) and not to our surprise, decreased activity in the reward seeking part of the brain (nucleus accumbens) . Dopamine, the “feel-good hormone” is a neurotransmitter. It’s associated with satisfaction, pleasure, and rewards. Eating a delicious meal, winning a game or helping someone in need caused a  surge of dopamine in the brain! Dopamine helps obtain goals, through the feelings of  pleasure-reward  and also helps us avoid unpleasant or painful stimuli. So, a lack of sleep caused decreased levels of dopamine and hence explains the misery we often feel when we lack sleep.

What is pain sensitivity and what does it do?

Another key brain region found to slow down in the sleep-deprived brain was the insula, which evaluates pain signals and prepares the body to respond. Even small changes in sleep patterns showed changes in pain sensitivity. This means that even slightly less sleep in a night showed that patients experienced higher levels of pain the next day. The self-preserving part of the brain analyses pain and picks our own body’s painkillers to kick in to help. However, a lack of sleep causes this mechanism to not work as efficiently. 



It’s really important to us at Vitality Physio to debunk myths and give answers to our patients about their pain. We will empower you to understand, manage, cure, and prevent injury.  Book with us for a free chat about your back pain and we can advise the best ways to help! Whichever stage of pregnancy you’re at, you can count on us to help you with your back pain.