Page 171 - ترم ثاني كتاب تمريض صحة الام الكتروني

171

• It is a bony landmark on the presenting part by which the position of the fetus is
known.

• In vertex presentation--------, the occiput is the denominator.
In face presentation → Mentum is the denominator.

In breech presentation→ Sacrum is the denominator
In Shoulder presentation → Scapula is the denominator
Position:

• It is the relation of the fetal back to the right or left side of the mother it is directed
anteriorly or posteriorly.
It is the relation of the denominator to the maternal pelvis.

In vertex presentation there are 8 positions:
1- Direct occipito-anterior (the occiput points \ towards the symphysis pubis).
2-right occipito-anterior (it points. towards the right ilio-pectineal eminence).
3-right occipito-transverse (it points towards the midpoint of the right iliopectineal

line).
4- right occipito-posterior (it points towards the right sacroiliac joint).
5-direct occipito-posterior (it points towards the sacral promontory).6-

6- left occipito-posterior.
7-left occipito-transverse.
8- left occipito-anterior.

• The commonest is the left occipito-transverse.
• Occipito-anterior positions are com-moner than occipito-posterior positions,

because of better accommodation between the concavity of the front of the fetus,
and the convexity of the lumbar spine of the mother.
• Left occipito-anterior is commoner than right occipito-anterior, because in the

former the head descends in the right oblique diameter of the pelvis, while in the
latter the head descends in the left oblique diameter of the pelvis, which is
reduced by the presence of pelvic colon. Also the right oblique diameter is

anatomically slightly longer than the left one due to the more frequent use of the
right leg. For the same reason, ROP is commoner than LOP.
Note: Cephalic presentation is more common than breech because the head is heavier
than the breech and because the breech is larger, it occupies the wide fundus.

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