During pregnancy your expanding uterus stretches and weakens your abdominal muscles and alters your posture, putting strain on your back.
The extra weight from your pregnancy also means extra work for your muscles and increased stress on your joints.
Hormonal changes in pregnancy can loosen the joints and the ligaments that attach your pelvic bones to your spine which can make you feel less stable (pregnancy waddle) and cause pain when you walk, stand or sit for long periods. This hormone, called relaxin, allows your baby to pass through the pelvis.
The altered shape of the pelvis and birth outlet that is caused by our upright stance; our babies need to twist and turn to navigate these unique bends. Even our nearest cousins, the great apes, have a near-straight birth canal.
However, in every other way, human birth is like that of other mammals — those animals that suckle their young — and involves the same hormones: the body’s chemical messengers. These hormones, which originate in the deepest and oldest parts of our brain, cause the physical processes of labour and birth, as well as exerting a powerful influence on our emotions and behaviour.
Researchers such as French surgeon and natural birth pioneer Michel Odent believe that if we can be more respectful of our mammalian roots, and the hormones that we share, we can have more chance of a straightforward birth ourselves.