Your baby is very active and involved throughout the whole process of labour. During the 1st stage, your baby rotates into position and tucks their head in (referred to as 'flexing their head'). In the 2nd stage (or pushing and birthing phase), your baby is preparing to leave the womb to meet you.
To do this your baby undergoes various movements called the 'cardinal movements'.
The cardinal movements consist of:
The descent
Flexion
Internal rotation
Extension of the head
Restitution
Internal rotation of the shoulders
Lateral flexion
Image 6-32 shows how the baby moves down the birth canal during the 2nd stage.
The descent. Descent takes place throughout the labour, as the baby's head negotiates the woman's pelvis. For women having their first baby, this journey often begins before the onset of labour, as the baby's head deeply engages. If this is your second or subsequent baby, this movement usually happens during the labour.
Flexion. Flexion happens throughout the labour. The top of uterus contracts down on the baby's bottom and legs, and 'propelling', or pushing the baby downwards, gently guiding their head towards the woman's cervix. With the uterus contracting, and the counter pressure from the cervix, the baby rolls into a ball, their head is tucked in (or 'flexes') so that their chin rests on their chest.
Internal rotation. As your baby's head is pushed downwards onto the springy pelvic floor muscle, there is a resistance that causes the baby to rotate around from the mother's side or back, to her front. The downward slope of the pelvic floor muscles (from the back of the woman's pelvis to her front) is similar in shape to a hammock. The pelvic floor encourages the baby's head to slip forward and rotate slightly, causes a slight turn in the baby's neck. This means that the baby's head is no longer in direct alignment with their shoulders, looking to their side, instead of down.