Center of Gravity
The center of gravity shifts upward and forward because of the enlargement of the uterus and breasts. This requires postural compensations to maintain balance and stability.

• The lumbar and cervical lordoses increase to compensate for the shift in the center of gravity, and the knees hyperextend, probably because of the change in the center of gravity.

• The shoulder girdle and upper back become rounded with scapular protraction and upper extremity internal rotation because of breast enlargement; this postural tendency persists with postpartum positioning for infant care. Tightness of the pectoralis muscles and weakness of the scapular stabilizers may be pre-existing to or perpetuated by the pregnancy postural change.

• The suboccipital muscles respond in an effort to maintain appropriate eye level (optical righting reflex), and to moderate forward head posture along with the change in shoulder alignment.

• Weight shifts toward the heels to bring the center of gravity to a more posterior position. This contributes to the “waddling” gait that is typically seen in pregnancy.

• Changes in posture do not automatically correct after childbirth, and the pregnant posture may become habitual. In addition, many child-care activities contribute to persistent postural faults and asymmetry.

Balance
With the increased weight and redistribution of body mass there are compensations to maintain balance.
• The pregnant woman usually walks with a wider base of support and increased external rotation at the hips.

• This change in stance along with growth of the baby makes some activities such as walking, stooping, stair climbing, lifting, reaching, and other activities of daily living (ADLs) progressively more challenging.

• Activities requiring fine balance and rapid changes in direction, such as aerobic dancing and bicycle riding, may become inadvisable, especially during the third trimester.

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