Cardinal Movements at Birth

03 Sep 2012 03:13 147
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The Seven Cardinal Movements
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Labor is a physical and emotional event for the laboring woman. For the infant, however, there
are many positional changes that assist the baby in the passage through the birth canal. Because
of the resistance met by the baby, positional changes are
specific, deliberate and precise as they allow the smallest
diameter of the baby to pass through a corresponding
diameter of the woman's pelvic structure. Neither care
providers nor the laboring woman is directly responsible for
these position changes. The baby is the one responsible for
these position changes ~ the cardinal movements.

Engagement or the entering of the biparietal diameter
(measuring ear tip to ear tip across the top of the baby's head)
into the pelvic inlet.

Descent
The baby's head moves deep into the pelvic cavity and is
commonly called lightening. The baby's head becomes markedly
molded when these distances are closely the same. When the occiput is
at the level of the ischial spines, it can be assumed that the biparietal
diameter is engaged and then descends into the pelvic inlet.

Flexion
This movement occurs during descent and is brought about by the
resistance felt by the baby's head against the soft tissues of the pelvis.
The resistance brings about a flexion in the baby's head so that the chin
meets the chest. The smallest diameter of the baby's head (or
suboccipitobregmatic plane) presents into the pelvis.

Internal rotation
As the head reaches the pelvic floor, it typically rotates to accommodate
for the change in diameters of the pelvis. At the pelvic inlet, the diameter
of the pelvis is widest from right to left. At the pelvic outlet, the
diameter is widest from front to back. So the baby must move from a
sideways position to one where the sagittal suture is in the
anteroposterior diameter of the outlet (where the face of the baby is
against the back of the laboring woman and the back of the baby's head
is against the front of the pelvis). If anterior rotation does not occur, the
occiput (or head) rotates to the occipitoposterior position. The
ocipitoposterior position is also called persistent occipitoposterior and is the common cause for
true back labor.

Extension
After internal rotation is complete and the head passes through the pelvis at the nape of the neck,
a rest occurs as the neck is under the pubic arch. Extension occurs as the head, face and chin are
born.

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