Biomechanical Changes During Pregnancy

The human body is a master at adapting to change, this includes physical, psychological, and hormonal change. A good example of this is when a woman falls pregnant, the body must adapt accordingly in order to carry and provide nourishment for another human life.

The associated weight gain, which is natural during pregnancy, requires the musculoskeletal system to adapt. These adaptations alter stance and gait, effecting posture and movements patterns compared to an unpregnant woman. The woman’s centre of mass will change as the baby grows to compensate for the altered gait and to improve stability due to the increased anterior load.

Hormonal changes will also affect the musculoskeletal system, such as the hormone Relaxin. Relaxin decreases stiffness in cartilage, joints and tendons and creates laxity in connective tissue to allow growth of the baby inside the woman’s uterus and more laxity (or loose ligaments) within the pelvis to facilitate an easier delivery


The overall postural effect of pregnancy by the final month is as follows:

  • Anterior tilt of the pelvis.
  • Hyperextended knees.
  • Increased lumbar lordosis.
  • Posterior shift of gravity line.
  • Hyper kyphosis of the upper thoracic spine.
  • Protracted shoulders.
  • Anterior angulation of the cervical region.
  • Extension of the occiput on atlas.
  • Associated with these postural changes is a waddling gait pattern.


Changes in the Spine

Due to the extra load on the anterior side of the spine, the lumber spine increases its curvature to balance out the load, decreasing falls risk. This increased lumber lordosis means that the thoracic compensates with a more than usual kyphosis.


Changes in the Knee

Compensation for the shift of centre of gravity can be seen when ladies hyperextend their knees, to help maintain their balance and keep an upright posture.

Laxity in the knees increases during the early stages of pregnancy and decreases significantly during the postpartum period.

If joint laxity continues following pregnancy, the woman may be exposed to an increased risk of OA and other joint pathologies.


Changes in the Ankle and Foot

An increase in the width and reduction in the arch of the foot occurs because of biomechanics changes during pregnancy.

Inflammation of plantar fascia can occur as a result of the reduced arch (flat foot)

The centre of mass relocates as the bodyweight increases, redistributing the plantar load, which is reported to be correlated with foot complaints


Changes in Gait

Due to the above-mentioned natural alterations, gait will be affected. The gait of pregnant women is characterised by slower speed as compared to the pre-pregnancy and postpartum state. There is also a significant decrease in the length of the gait cycle and an increase in double support time compared to post-partum.


The human body is amazing at adaptation, and pregnancy is a good example of how it can manage change. Exercise can be a very beneficial management strategy, if done with professional direction and guidance. Strengthening the joints and improving gait mechanics can help relive associated pain and tension resulting from the musculoskeletal changes, as well as reduce falls risk. Exercise can be viewed as a way to assist and help the body through the changes which naturally occur during pregnancy, not only helping manage pain but also boost mood and prevent injures.