What happens to your back and pelvis when you are pregnant?

Why is it sore? Between 50-80% of pregnant women will report SIJ (pelvis) or lumbar spine pain throughout their pregnancy. This pain is associated with the biochemical and structural changes during pregnancy and throughout postpartum (ie after giving birth) while the mother is still breastfeeding. When you are pregnant the hormone relaxin is produced and it continues to rise during the 1st trimester and in the final weeks of pregnancy. This hormone as the name suggests “relaxes” or loosens the muscles, tendons and ligaments in the body in order to allow the body to accommodate the growing baby. This hormone also breaks down collagen and prevents it from being synthesized. So what does all this mean? Well firstly, the increased weight of the belly means your pelvis tilts forward and as a result, your back compensates by arching back further i.e. the curve in your back deepens in order for you to maintain your balance. This “hyperlordotic” position can then cause the joints in your back to jam up and be irritated as the normal lubrication and movement through them is reduced. What about the pelvis? The joint between your pelvis (the illium) & your spine (the sacrum) is called the sacroiliac joint (SIJ). Normally the rough, groove like connecting surfaces of the sacrum and ilium interlock and help stabilise the joint. However when you are pregnant the relaxin hormone loosens and widens the joints at the front and back of the pelvis (SIJ and pubic symphysis) which reduces their stability and changes the efficiency of the muscles which attach around that region. Essentially the joint itself is loose, the ligaments become lax, and the muscles which usually stabilise the pelvis aren’t able to work as efficiently. When you put all this together with the increased load on the baby you have an unstable pelvis which often causes pain.

Trauma at birth can also tear or loosen some of the ligaments in the pelvis. The pain around the pelvis will typically be a dull ache but can become a sharper pain with activities like standing from a seated position, climbing stairs and getting out of the car. Usually its on one side but can be across both, and the pain can refer down to the buttock or back of the thigh.

What can l do?

  • avoid excessive unilateral (ie on one leg weight bearing activities eg excessive twisting, lifting, single leg stance postures, stair climbing.
  • Get out of a chair or car with even weight through both feet.
  • Sleep on your side with a pillow between your legs and under your pelvis.
  • Get a physio to teach you how to train your core muscles as research has shown that these muscles are very important in stabilising your lower back and pelvis (they act like a corset around your low back and pelvic region).
  • Avoid lying on your back for long periods of time, particularly after 19 weeks of pregnancy. This is because the weight of the baby and uterus can compress blood vessels & reduce the blood flow to the placenta and baby.
  • When standing, maintain a good posture to alleviate the stress in your back and pelvis.
  • Stand upright as though someone is pulling on a string attached to the top of your head.
  • Keep your abdomen and buttocks pulled in to reduce the curvature in your lower back. Do not hold your breath.
  • Keep your knees slightly bent when standing as locking the knees can increase the amount of curvature on your lower back.
  • When sitting, choose a good straight backed chair and avoid slouching. Bend with your hips and not your back.
  • Avoid lifting or carrying heavy objects.
  • Reduce your stride length.
  • A maternity belt around the pelvis can provide some relief as it re-stabilises your pelvis. Speak to your physio for this.
  • Start training you pelvic floor muscles to prevent incontinence happening:
    • try to not go to the toilet on the first urge, but wait till the second urge
    • think of your pelvic floor muscles (muscles that allow you to hold your urine in) as a hammock and gently draw them up towards your belly; perform 10x 10 sec holds daily
    • using those same muscles perform 10 strong contractions (no need to hold these)

Pregnancy can be a tricky time for low back & SIJ pain, and often new mums find problems in these areas once they are caring for their baby as well. There is a lot that can be done to help re-stabilise your low back and pelvis to reduce these problems, and also advice about common daily activities that can help you reduce the strain you put through your back. If you are not sure then please chat to us or your local physio about how we can help you enjoy this exciting time of your life!

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