Page 35 - 33Elctronic Book (3) Normal Labor

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Summary In Study Session 1A&B, you have learned that:

1. The bony pelvis is composed of the ilium, ischium, pubic bones and sacrum.
2. The size and shape of the bony pelvis can affect the ease or difficulty of labor
and delivery; a broad pelvis gives less difficulty than a narrow one, which may
obstruct the descent of the fetus down the birth canal.

3. Certain landmarks in the anatomy of the pelvis are commonly used to estimate
the descent of the fetus during labor and delivery. The two most important

landmarks are the ischial spines and the sacral promontory, which can be felt
with the fingers during a vaginal examination.
4. The pelvic inlet is the space where the fetal head enters the pelvis; it is larger
than the pelvic outlet, where the fetal head emerges from the pelvis. In order to
get through the widest diameter of the inlet and the outlet, the fetus has to rotate
as it passes through the pelvic canal.

5. The skull is formed by several bones joined tightly together by joints called
sutures. In the fetus and newborn, spaces called fontanels exist between some of
the skull bones on the top of the fetal head. The position of the sutures and the
fontanels can tell you about the angle at which the fetal head is presenting during

labor and delivery.
6. The vertex presentation (where the top of the fetal head is the presenting part) is
the most common and the safest presentation for a normal vaginal delivery. Other
presentations carry a much higher risk for the mother and fetus.

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