My premise here at Spinning Babies is that the position a baby starts labor in is determined mostly by uterine balance which then leads to availability of space in the lower uterine segment. Uterine shape is part genetics and partly due to the degree of balance of the womb. You can read more about this in The Three Principles.
The way a baby moves through the pelvis is called the cardinal movements.
Typically, these cardinal movements are discussed in 7 key, or cardinal, steps.
The wide part of baby’s head dips below the pelvic brim. Typically, for the first time mother, this occurs before labor, often at 38 weeks.
Baby’s chin touches the chest for full flexion.
The baby lowers, or comes down. Descent is actually happening inbetween every other cardinal movement repeatedly. In other words, the baby must descend to engage. Then the baby descends a bit more to flex. The baby descends again before extension and then again during extension before restitution. Finally, descent is the action of expulsion.
4. Internal rotation
The baby’s head rotates inside the pelvis. From whatever position the head was in when engagement occurred at the brim, the head next rotates on the pelvic floor to fit the midpelvis and after more descent rotates to the front and back diameter to fit out of the outlet.
After navigating the opening through the pelvic floor, the baby’s back extends pushing the head further through the outlet. Many books simply state that the head extends and misses the fact that the baby’s spine is the origin of extension.
6. Restitution (or external rotation)
The baby’s head is out, usually in the OA position while the baby’s chest is rotating in the pelvic floor. The baby’s head is then seen to rotate to follow the chest rotation. Some babies first rotate externally1/8th of the circle, and then another 1/8th, or seen to rotate ¼ of the circle to face the mother’s thigh.
The baby’s anterior shoulder presses on the firm tissue just under the pubis. A tiny bit of pale flesh of the anterior shoulder is seen in the front. The pressure of the anterior shoulder pivots the posterior shoulder down, allowing the posterior shoulder to swing out the arc of the sacrum. The posterior shoulder is then born first. This is assuming no one has grasped the baby and forced the anterior shoulder out first, a common habit.
The baby will continue to spiral out, and the hips may need to be lined up in the Anterior-posterior diameter with the opening of the pelvic floor for the large baby’s legs to emerge. But this is rarely noticeable.
Continue on to the Membership Section of SpinningBabies.com if you would like to examine the cardinal movements, including engagement variations amongst the four pelvic types. The Membership Section explores the Spinning Babies perspective in detail and offers more childbirth education resources. Visit the Membership Description page for more information.
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