Pain During Pregnancy: An evolutionary/osteopathic perspective

Dr. Edmund Bruce-Gardner

Being pregnant can suck.  Although many of us, like me, will never really know what it is like, we will (in all likelihood) all know someone who is (or has been) pregnant; and if you don't believe me: ask them!

Pregnancy could mildly be described as a time of some changes. The process of growing another human is a complicated one, and it will put stresses and strains on your body it will never have experienced before.

Apart from the constant tiredness, morning sickness, cravings, swelling, mood swings, and breathlessness, some not-small percentage of expectant mothers will also suffer from various aches and pains.  These are most commonly experienced in the low back and pelvis, but (particularly in the later stages) will often be reported in the mid/upper back, thoracic cage (i.e. ribs), shoulders and neck.

To understand some of these issues, it is helpful to go back to a beginning. Not the beginning, of course!

So, about six million years ago, plus or minus, our ancestors started walking on two legs, a trait called bipedalism.

This necessitated a whole host of changes, many of which might be considered a bit 'bodgy', as they were a cobbled-together adaptation of existing structures rather than a redesign, so to speak. 
​

I allude to this in my blogs on the shoulder, and the knee, in explaining why they so often develop similar issues in people all over the world, with very different lifestyles.

These changes have particular relevance in pregnancy, because many of them involved the way that the pelvis and spine fit together and work

As the orientation of the skeleton became more upright, changes to the shape of the pelvis and hips, muscle alignments and even the bony ridges and features have forced us accept a number of trade-offs. ​

It is worthy of note that these trade-offs are not necessarily minor; arthritis appears to have been an issue, especially in the low back, pelvis and knees, since hominids developed bipedal locomotion.

The spine developed a number of curves, helping us to bring our body weight over our hips (or, more accurately, to align the gravitational centres of head, thorax and abdomen) and cushion the brain from the shock of ground-reaction forces from walking.

The femurs (thigh bones) turned to point more inwards, bringing our feet more directly under the centre of our bodies.

The pelvis became much shorted and bowl-like, giving better leverage to the hip muscles. The pelvis also got larger as we shifted from a quadrupedal (four-legged) to bipedal (two-legged) stance, and the abdomen relatively smaller.  This means that limited space for abdominal expansion during pregnancy.

This in turn leads to several problems, including 'squeezing' of the foetus between the anterior (front) abdominal wall and the lordosis (inwards curve) of the lumbar spine; and consequent compression of the large blood vessels in the region and forward expansion of the abdomen.

(a) Pan (chimpanzee) (b) Australopithecus (human ancestor) (c) Human female (d) Human male (From Lovejoy, 2005)

​The birth canal has changed from a horizontally-oriented cylinder to a vertically-oriented curved tube, presenting much more resistance to the poor baby as it tries to descend through this awkward, narrow passageway.  

This is exacerbated by the increase in head size (due to our wonderful, complex, massive brains) that human babies developed over the course of our evolution.

The implications of some of these changes are more obvious, especially with regards to giving birth.  However, what does this all mean with respect to pain and pregnancy?

Early in pregnancy, in the first trimester, there is normally a slight posterior rotation (bacwards tilt) of the pelvis caused by displacement pressures of the other organs.  This actually flattens out the curve in the low back, which puts a little more strain on the lumbar erector spinae (muscles that hold you upright and support that curve).  It also stretches the hip flexors (muscles at the front of the hip) and forces some contraction in the upper abdominal muscles at the front.

Towards the end of the first trimester, the abdomen as a whole is starting to change shape and orientation.  As the uterus enlarges, pressure will be placed on the diaphragm (the dome-shaped muscle between thoracic, or chest, and abdominal cavities), forcing the region between the mid- and low back into extension, or backwards bending.

Early postural changes in pregnancy. From Stone (2007)

The majority of breast changes also take place in the first half of pregnancy, and the increased weight can pull forwards, increasing the roundedness of the shoulders and upper back curve, and of the inwards curve in the bottom of the neck.

Late postural changes in pregnancy. From Stone (2007)

Later in pregnancy, the pelvis has commonly started to rotate anteriorly (forwards), with a consequent re-organisation of spinal curves.  Now there is an increase in the lumbar lordosis, which places a strain on the abdominal muscles. This may also increase the pressure on the pubis and lower end of the ribs, and/or pelvic floor and pelvic ligaments.  The head position will also shift, increasing strain at the junction of neck and upper back.

All of these contribute to the classic 'waddling' gait of pregnancy.  Each person will apply different strategies while walking to cope with these underlying changes, so an individualised assessment of your compensatory mechanisms is essential to effective management.

TL:DR pregnancy is a time of massive changes throughout your whole body. 
How well you cope with these shifting stresses and strains determines how much discomfort you are likely to suffer. 
Some of the structures in the body have been adapted on-the-fly to cope with the transition from walking on all fours to two legs.
Unfortunately the areas where this is most true are also fundamentally involved in pregnancy and childbirth.
By assessing just how your structure and function are compensating for each other, your osteopath can help to make this wonderful, exciting - but potentially uncomfortable - time as easy as possible.