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Relaxin – Friend or Foe During Pregnancy?

Published: 16 December 2013

During pregnancy your body produces increased amounts of a hormone called Relaxin which has many physiological effects including:

  • Intrauterine ligaments relax to allow for expansion of your uterus to accommodate the growing placenta and foetus;
  • Increased elasticity and relaxation of muscles (including abdominal and pelvic floor muscles);
  • Arteries relax so they may expand to accommodate a 30-50% increase in your blood volume.  This in turn ensures your blood pressure doesn’t go through the roof;
  • Ligaments (which run between the bones of your body to provide joint stability) soften which means your joints have increased flexibility.  You may think this sounds great if you are usually quite stiff and could never do the splits – but looser ligaments can be a real nuisance to pregnant women.

Exercise choices and daily activities often need to be modified during pregnancy to decrease the risk of muscle and/or joint injury.  High impact exercise could lead to sprained knees or ankles or increased stretch and damage to the pelvic floor.  Heavy or poor lifting technique puts you at higher risk of back strain or disc prolapse.

Relaxin’s most valuable effect on ligaments is of course to the pelvic girdle (which is the pubic symphysis or joint at the front of the pelvis and the two sacroiliac joints at the back of the pelvis).  These pelvic joints need to be hyper-mobile to allow for the passage of the baby during childbirth.  Unfortunately, these pelvic joints don’t just loosen up right before your due date.  Women can experience varying degrees of pelvic joint instability throughout pregnancy and approximately 45% of all pregnant women suffer from pelvic girdle pain.  If you experience pelvic girdle pain in one pregnancy you do have a high risk of repeated episodes in subsequent pregnancies, but the severity cannot be predicted.

Symptoms of pelvic girdle pain could include any of the following:

  • Pain in the groin, pubic area, buttock, lower back or back of the thighs;
  • Pain could be unilateral or bilateral;
  • Clicking or locking sensation in the pelvic joints;
  • Aggravating activities could include walking (may feel like you are waddling), standing on one leg, up/down stairs, in/out car, rolling in bed, carrying heavy items in one hand.

Physiotherapy can assist greatly with managing your pelvic pain until your bundle of joy arrives.  Treatment can include provision of pelvic stability braces or crutches (for more severe cases of dysfunction), pelvic joint taping, hot/cold therapy, soft tissue massage techniques, strengthening exercises for the abdominal and pelvic floor muscles and education and advice around lifestyle modification to avoid aggravating activities.

It is important that your birthing team are aware you have pelvic instability as certain positions such as wide legs in stirrups should be avoided if possible.  In most cases, pain associated with pelvic instability disappears within a few weeks of birth, but in more severe cases you may need ongoing treatment.

Nicole Tayler – Physiotherapist, Back In Motion Patterson Lakes