One of the jobs of the hormone changes in mum’s body is to allow for expansion to occur without injury. The effects of relaxin and progesterone are at the site of ligaments, tendons and fascial connections. Pre-existing faults / injuries / strains can become accentuated during pregnancy. Ideally you would have a pre pregnancy check up and have monitoring appointments during your first trimester.
In the second trimester the imbalances start to become noticeable, meaning uncomfortableness. Placing greater pressure on particular components of the body.
Imagine for a second your core prior to pregnancy multiplied by a factor of enlargement to give you the core that enables you to deliver a baby.
Feelings of shortness of breath and fullness can be a sign of muscular imbalance.
Upper back tension as your centre of gravity shifts can signify imbalance as well as rib pain.
Rib pain is very common and occurs because the coordination and strength of the abdominals as they expand are out of balance. Typically ribs 6-10 will become posturally speaking rigid. Giving rise to intercostal neuritis. Following this heartburn and then body torsion in the abdomen (wonky bump).
Under torsion the spine is not stable and as the hormone relaxin rises the pelvis becomes less able to support an unstable core. This is why at an extreme example some women are on crutches leading up to their delivery, whilst others find it difficult to stand in a queue (weight bear).
If an imbalance is present in the hips then the trochanteric (hip) expansion cannot take place and thus the expansion pressure laterally is placed onto the pubis symphysis causing PSD.
Add all the imbalances up together and imagine your muscles pushing baby out… Are you going to be balanced enough to push down through the centre or are you off centre in some way?