The Legend of Relaxin
Is relaxin ruining your life?
TLDR: probably not.
Is relaxin the cause of your pregnancy pain?
Again, probably not.
There’s a super pervasive myth that relaxin is the obvious explanation for so many things: loose ligaments, joint pain, the feeling of turning into a noodle during pregnancy. It’s believable. It’s even kind of cute; the hormone is literally called “relaxin;” of course it gets blamed for instability.
But what if relaxin is not the problem?
If we critically think about what this hormone does and doesn’t do, we can confidently say that blaming relaxin for every pregnancy-related ache might actually be holding pregnant people back from effective care.
So what’s actually up with relaxin?
Relaxin is a hormone produced by the placenta and ovaries during pregnancy and in larger quantities than when someone is not pregnant. Relaxin does work on the pelvis to soften connective tissue, but its main job is to support growth of the uterus and prepare the cervix for a potential vaginal birth.
Relaxin is not a blanket of instability for the whole body. Rather, the effects are targeted and specific because our bodies are extremely smart and efficient.
Timing of relaxin: peak and plateau
Most of the time, pregnancy pain happens in the second and third trimesters, but guess when relaxin levels are at their highest?
The peak is quite early in pregnancy: around week 12-14. It falls quite a bit after that and then level stays pretty stable. It’s also much higher in people carrying multiples. So if relaxin is the cause, we should see the worst symptoms in the first trimester and in people gestating twins, but that’s not what we see.
Myth #1: relaxin is making all my joints unstable.
Current available research shows no relationship between blood relaxin levels and measured or perceived joint instability or pain.
There’s a lot of redundancy built into the body system for a reason. There are many components to stability, meaning you are definitely not made of jello even if it feels like you are. Sometimes the body just needs movement or other supportive strategies to help develop the neuromuscular adaptations for control that it may be craving.
There’s no arguing that a pregnant person’s body changes dramatically during this transition, but the body is well equipped to manage these changes.
Myth #2: I’m in pain because everything is just too loose.
The established risk factors for pregnancy-related pelvic girdle pain are:
previous history of low back pain (the system is primed for this already)
multiparity (meaning more than one pregnancy. There can be some sensory redistribution due to a previous pregnancy or injury and people with kids often have lower energy reserves.)
dissatisfaction with work
psychosocial factors
Catastrophizing (imagining the worst possible outcomes)
Fear-avoidance behaviors (avoiding movement because of pain or fear you’re causing tissue damage)
Emotional distress (like anxiety or depression)
Belief that the pain will not improve
family history/genetic predisposition (may be related to expectations or certain behaviors)
Some of these, like negative expectations, can unfortunately even stem from a conversation with a well-meaning healthcare provider. This is an example of the phenomenon called nocebo (the opposite of placebo). This means someone can experience more pain or other symptoms simply because they expect it.
Expecting a bad outcome can physiologically create one.
Just to be clear, having one or more risk factor DOES NOT mean pain is inevitable. There are plenty of people with many of these risk factors who never develop pregnancy-related pain.
Myth #3: You just have to deal with pain until relaxin goes away.
No! Stop! Who told you that?!
Symptoms can absolutely improve or disappear during pregnancy. Say it out loud! Tell your friends!
It can definitely help to work with someone who understands the neuroscience of pain and pregnant bodies, with extra glitter if they also use a biopsychosocial framework and have some training in mental health. (Like me! Occupational therapists are perfect for this.)
Here are some things my patients typically find helpful:
Strength training: muscles need to be loaded to feel safe. Glutes, abdominal muscles, and adductors can improve perception of pelvic girdle stability and efficiency of load transfer
Education on breathing mechanics and pressure management can help you keep the ribcage mobility you need for better diaphragmatic movement. The pelvic floor and the nervous system respond to movement of the diaphragm to stay balanced and help you achieve a solid parasympathetic (rest and digest) state when you need to. Breathing can change a lot in pregnancy because there’s just less room for the diaphragm to descend.
Support garments and taping can give external feedback to the nervous system to keep everything feeling safe and supported. This does not mean anything is unstable! External support is not holding you together; it’s just giving your nervous system some safety information so you can move better and your muscles can react to the demands placed upon them instead of gripping all the time. The pelvis is resilient with or without your sacroiliac belt.
Manual therapy can reduce pain, but again it’s because we’re communicating with the nervous system. Your therapist’s hands are not “correcting your alignment” or “putting you back into place.” We are just helping calm the nervous system. Your brain is in charge of changing your muscle tone and your overall level of sensitivity.
We need to move beyond these biomechanical explanations for all pain, including the pain experienced by pregnant people! The tissues can certainly play a role, but it’s not because of instability from relaxin. Other hormones can also change the sensitivity threshold for pain and fatigue, but that’s another blogpost.
This research comes from Dr. Sinead Dufour and her team in Ontario, Canada. If you’d like to read more, here is a link to the infographic they made.
My favorite quote from the infographic is:
“The strongest predictor of resolution of pregnancy-related pelvic girdle pain (PPGP) is having the belief that it will go away.”
Your body is resilient. Don’t let your healthcare provider dismiss you and blame your pain on relaxin. See someone to get properly assessed and help you with a plan to build your capacity for life while pregnant.
This content is for informational purposes only and is not medical advice. Please consult your qualified medical provider for an individual assessment or plan of care.
Reference:
Pulsifer, J., Britnell, S., Sim, A., Adaszynski, J., & Dufour, S. (2022). Reframing beliefs and instiling facts for contemporary management of pregnancy-related pelvic girdle pain. British journal of sports medicine, 56(22), 1262–1265. https://doi.org/10.1136/bjsports-2022-105724
