Download Normal Pelvis, types of female pelvis and fetal skull

Bony pelvis :
it is made up of four bones : the sacrum , coccyx ,
and two innominates (composed of the ilium ,
ischium ,and pubis).
•The false pelvis is
bordered by the
lumbar vertebrae
posteriorly , an
iliac fossa
bilaterally ,and the
abdominal wall
anteriorly .
•It supports the
pregnant uterus .
•The true pelvis is a bony
canal and is formed by the
sacrum and the coccyx
posteriorly and by the
ischium and pubis laterally
and anteriorly .
•The posterior wall is twice
the length of the anterior
wall.
•The true pelvis is area of
concern because its
dimensions are sometimes
not adequate to permit
passage of the fetus .
 The pelvic inlet
 The plane of greatest diameter
 The plane of least diameter
 The pelvic outlet
Pelvic Planes
Anterior
Posterior
sacral
promontory
Lateral
iliopectinaeal
line of the
innominate
bones.
1- The Pelvic
Inlet
pubic crest
2- The Plane of
greatest
diameter
posterior
junction of S2
midpoint of the
& S3
pubis
upper part of
the obturator
foramina
3- The Plane of
least diameter
(Mid-pelvic
Plane)
Lower edge of
pubis
Lower sacrum
ischial spines
and
sacrospinous
ligaments
4- The Pelvic
Outlet
lower pubic
bone
sacrococcygeal
joint
ischial
tuberosity
The diameters of the pelvic planes represent the amount
of space available at each level .
Pelvic inlet has five important diameters :
 The anteroposterior diameter : described by one of two
measurements:
the true conjugate (anatomic conjugate ): from
sacral promontory to superior pubis
obstetric conjugate: from sacral promontory to
posterior pubis .
 The transverse diameter : the widest distance between
iliopectineal lines
 Two oblique diameters :from sacroiliac joint to the
opposite iliopectineal eminence
 The posterior sagittal diameter: from AP & transverse
intersection to the middle of sacral promontory
 The anteroposterior diameter : from the midpoint

of the posterior surface of pubis to the junction of
S2 and S3 vertebrae .
The transverse diameter : widest distance
between the lateral borders of the plane (upper
part of obturator foramina )
 The anteroposterior diameter :extends from the
lower border of the pubis to the junction of S4 and S5
.
 The transverse (bispinous ) diameter : extends
between the ischial spines .
 The posterior sagittal diameter : from midpoint of
bispinous diameter to the junction of S4 and S5
 Anatomic anteroposterior diameter :from the



inferior margin of pubis to tip of coccyx
Obstetric anteroposterior diameter : from inferior
margin of pubis to sacrococcygeal joint .
Transverse diameter : between the inner surface
of ischial tuberosities
Posterior sagittal diameter : from middle of
transverse diameter to the sacrococcygeal joint .
Gynecoid
Android
50%
30%
Anthropoid
Platypelloid
18%
2%
 Round at the inlet
 Side walls stright
 Ischeal spines of average
Cylindrical shape
prominence
 Well-rounded sacrosciatic notch
 Well-curved sacrum
 Spacious subpubic arch, with an
angle of approximately 90 degrees
 Triangular inlet
 Convergent Side walls
 Shallow sacral curve
 Long and narrow sacrosciatic
notch
 Narrow subpubic arch
 It is the typical male type
 Long narrow oval inlet (AP>transverse)
 Side walls that not converge
 Ischial spines close, owing to overall
shape
 Variable, but usually posterior,
inclination of the sacrum
 Long sacrosciatic notch
 Narrow, outwardly shaped subpubic
arch
 Oval-shaped inlet (AP<transverse)
 Straight or divergent side walls
 Ischial spines close, owing to
flat shape
overall shape
 Posterior inclination of a flat
sacrum
 Wide bispinous diameter
 A wide subpubic arch
 For assessment of obstetric capacity, most important
measurements are:
 Obstetric conjugate of inlet
 Distance between ischial spines
 Subpubic angle & bituberous diameter
 Posterior sagittal of three planes
 Curve & length of sacrum
- It is only an estimate
- The best time is late in
pregnancy when the
soft tissue are
distensible
 palpate the SACRUM
 It should be concave. Flat or convex is abnormal
 midpelvis and pelvic outlet: can’t accurately be
measured clinically but it can be estimated through
clinical examination.
 Its purpose is to aid in determining the need for C-S.
 Other factors affecting need for C-S include: Fetal size, Force of
contractions, & Position of fetus, & degree of molding
 It is an accurate measure
 Indications:
No longer needed in cephalic presentation
Breech delivery
To rule out pelvic abnormalities either inherited
or traumatic
 2 films are needed
Lateral view – AP diameter
Inlet view – transverse diameter
 General characteristics
 Sutures,Fontanelles and bones
 landmarks
 Diameters
 Cephalic pelvic disproportion
Fetal Head:
is the Largest and least compressible part of the fetus
fetal skull: 1-base
2-cranium
Base
Large, ossified, firmly united and noncompressible
Cranium (Vault)
•Consists of occipital , parietal , frontal
and temporal bones
•At birth thin, weakly ossified, easily
compressible and interconnected only by
membranes
Protects the vital structures within the
brainstem
allows molding
 Definition:
 The membrane occupied spaces between the
cranial bones.
 The membrane filled spaces located at the point where
the sutures intersect.
Characteristics
Closure
(ossification)
Anterior
Fontanelle
(bregma)
Diamond shape
and found at the
intersection of
sagittal , frontal
and coronal
sutures
2-3 cm (larger)
18 months of life
Posterior
Fontanelle
Y or T-shaped and
found at the
junction of the
sagittal and
lambdoid sutures
6-8 weeks of life
(bregma)
5
3
6
(lambda)
2 Glabella
1 Nasion
7
1- Nasion : root of the nose
2- Glabella: elevated area between the orbital ridges
3-Sinciput(brow):the area between anterior fontanelle
and glabella
4- anterior fontanelle(bregma)
5- vertex the area between the fontanelles and bonded
laterally by the parietal eminence
6- posterior fontanelle ( lambda)
7- occiput the area behind and inferior to the posterior
fontanelle and lambdiod sutures
Antero-posterior diameters( 4 )
Transverse diameters ( 2 )
Length
Definition
Presentation
Suboccipitobreg
matic
9.5cm
Extends from
occipital bone at
the junction of the
neck to AF .
When the head is
well flexed as in
occipitoanterior or
occipitotransverse
Submentobregm
atic
9.5cm
from junction of
in the face
neck and lower jaw presentation
to AF.
Occipitofrontal
11cm
from external
occipital
protuberance to
glabella.
As in
occipitoposterior
presentation
Supraoccipitome
ntal
13.5cm
from vertex to
chin.
In a brow
presentation ( lead
to CS )
1. Biparietal(9.5cm):
between the parietal
bones.
2. Bitemporal(8cm):
between the temporal
bones
 An obstetric condition where there is mismatch in
size between (fetal head & the maternal pelvis),
resulting in failure of the fetus to pass safely through
the birth canal for mechanical reasons.
1- Absolute CPD: There is no possibility of a normal
vaginal delivery (extremely rare).
 Fetal (Temporary):
 macrosomia (diabetes) & Fetal hydrocephalus
 Maternal (Permenant):
 Congenitally abnormal pelvis.
 Damaged pelvis (RTA).
 Distorted pelvis (osteomalacia).
2- Relative CPD: the baby is large but would pass
through the pelvis if the mechanisms of labor
function correctly.
 If, however, the head is deflexed or fails to rotate in
the mid-cavity, then prolonged, abnormal labor will
occur.
 CPD:
 Can only truly be diagnosed after a trial of labour.
 May be suspected antenatally in women who are ≤ 1.58m
height.
 Should be suspected in a women with a high head at
term, after excluding the other causes.
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