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THE BONY PELVIS
DR. AHMED ABDULWAHAB
Assistant Professor,
Consultant
OBGYN Department
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In women the pelvis has specialform that adapts to childbearing .
It is composed of four bones .
The sacrum coccyx and twoinnominate bones ..
The innominate bone is formed bythe fusion of the ilium ,ischium, andpubis
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The true pelvis is the portionimportant in childbearing , isbounded above by promontory andalae of the sacrum the lineaterminalis and the upper margin of
the pubic bone , and below by thepelvic outlet .
Ischial spines are of great obstetrical
importance because it is the shortestpelvic diameter and has a valuablelandmarks in assessing the level of
the presenting part of the fetus
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The sacrum form the
posterior wall of the pelvisand it is curved toaccommodate the rotating
head .The promontory may be felt
on vaginal examination andprovide a landmark forclinical pelvimetry
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Pelvic joints
Symphysis pubis where pelvicbones are joined togetheranteriorly
Sacroiliac joint where pelvic
bones are joined
posteriorly .
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Planes and diameters of the
pelvisFour imaginary planes
1- the plane of pelvic inlet
2-the plane of pelvic outlet
3- the plane of mid pelvis
4
the plane of greatest
pelvic dimensions
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Pelvic shapes 1-gynecoid pelvis the inlet is
slightly oval or rounded , theischial spines are not prominent ,the pubic arch is wide , sacrum is
well curved .
Android pelvis is a deep andconvergent with prominentischial spines , narrow sub-pubicarch and straight sacrum .
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Pelvic inlet measurement
Diagonal conjugate it is the distant
from the sacral promontory to thelower margin of the symphysis pubis.
True conjugate from sacral
promontory to upper border ofsymphysis pubis
Obstetric conjugate from sacral
promontory to mid of posterior aspectof symphysis pubis subtract 1.5-2.0 cmfrom diagonal conjugate
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The mid pelvis at the level
of ischial spines the inter-spinous diameter is 10 cm .
Pelvic outlet clinically it isthe distant between theischial tuberosities it isaround 8.0 cm
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THE FETAL SKULL
BONES
Two frontal bones separated by frontalsuture.
Two parietal bones separated by sagittalsuture .
Two coronal sutures between frontal and
parietal bones .
Two lambdoid sutures between parietaland occipital bone .
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Sutures meet at an irregular space formswhich is enclosed by a membrane called
fontanel . Anterior fontanel is a lozenge shape
between the two frontal and two parietalbones usually it is opened .
Posterior fontanel at the junction of thetwo parietal bones and occipital bone .
It gives an important informationconcerning presentation and position of
the fetus.
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Fetal head diameters
Subocipoto-bregmatic 9.5 cm vertexpresentation.
Submento-bregmatic 9.5 cm facepresentation.
Mento-vertical 12.5 browpresentation .
Biparietal diameter 9.5cm .
Occipto-frontal 10.5 cm
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Occipital bone is the landmark invertex presentation.
Mentum is landmark for face
presentation, Frontal bone is land mark for brow
presentation
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labour
Definition.
It is the onset of painful, regular
,contractions, more than one every ten
minutes. With progressive cervical
effacement and dilatation
accompanied by descend of the fetal
presenting part.
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Stages of labor
Labor is divided in to three stages.
1ststage from diagnosis of labor till fulldilatation of the cervix.
2ndstage of labor from full dilatation ofthe cervix till delivery of the fetus.
3rdstage from delivery of the fetusuntil delivery of the placenta.
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The duration of labor
Primigravida about 12 hours .
Multigravida 8.0 hours
The moral of most women deteriorateif labor is prolonged .
There is greater incidence of fetal
hypoxia after long labor.Greater incidence of operative vaginaldelivery.
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DESCENT.
It is secondary to uterine action in 1stand early phase of 2ndstage of labor .
FLEXION
When the head descent to the narrowmid-cavity flexion should occur.
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INTERNAL ROTATION .
The shape of the bony pelvis and direction ofthe pelvic floor muscles in addition to thewell flexed head will help the head torotate the head into the occipito anterior
position .
In a well flexed head the occiput will meetthe pelvic floor and will guide the direction
of the rotation
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EXTENSION.
The head is deliver by extension firstthe bregma ,face , and chin appear insuccession over the posterior vaginalopening and perineal body.
RESTITUTION.
As soon as the head escape from thevulva the head aligns itself with theshoulder
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EXTERNAL ROTATION.
In order to deliver the shoulders haveto rotate into the direct anterior-posterior plane .
The doctor will rotate the head makingthe face of the fetus looking tomedial aspect of the maternal thigh .
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Delivery of the shoulders .
The anterior shoulder is under thesymphysis pubis and deliver first
,and the posterior shoulder deliver
subsequently
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THIRD STAGE OF LABOR .
Separation of the placenta
occurs because of the
reduction of the volume of the
uterus due to the uterine
contraction and retraction
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