CPD

1. CPD

2. ANATOMY OF PELVIS

BONES
ILIUM
ISCHIUM
PUBIS
SACRUM
COCCYX

3. ANATOMY OF PELVIS

DIVISION
1. FALSE PELVIS (PELVIS MAJOR)
• Above PROMONTORY
the linea terminalis
SACRAL
•LINEA
No obstetric significance
ARCUATE
LINE
TERMINALIS
PECTINEAL LINE
2. TRUE PELVIS (PELVIS MINOR)
• Below the linea terminalis
• Important in childbearing
• Forms the bony birth canal

4. PLANE AND DIAMETERS

1. Pelvic Inlet (Superior
Strait)
2. Pelvic Outlet (Inferior
Strait)
3. Midpelvis / Plane of Least
Pelvic Dimensions
4. Plane of Greatest Pelvic
Dimension

5. PLANE AND DIAMETERS

PELVIC INLET
It refers to the brim of the
pelvis.
Shape:
almost round
The
angleIt
ofis
inclination
may be
(gynecoid)
with of
the
antero
lessened
in case
lumbarization
of
posterior
the and
first
piece diameter
of sacralbeing
vertebra
isshortest.
called low inclination. It has
The
of the
inlet makes an
got
noplane
obstetric
significance.
It
angle of
about 55 degree
actually
facilitates
early with the
horizontal and is called angle of
engagement.
inclination
SACRAL
ANGLE: .
It is the angle formed
of inclination
is
byWhen
the the
trueangle
conjugate
with the first
increased
due
to sacrum.Normally,it
sacralization of
two
pieces of
the
lumbar
it is called
isfifth
greater
thanvertebra,
90°
high inclination.

6. PLANE AND DIAMETERS

DIAMETERS
PLANE AND
DIAMETERS
1.Anteroposterior
2. Transverse
3. Right and left
oblique

7. PELVIC INLET DIAMETERS

ANTEROPOSTERIOR
PELVIC INLET DIAMETERS
TRUE
CONJUGATE
1. THE
OBSTETRIC :11cm
CONJUGATE
• Line drawn from midpoint of
2. THE DIAGONAL CONJUGATE
sacral promontory (SP) to upper
OBSTETRIC
CONJUGATE:10cm
3. THE
ANATOMICAL
border
of
pubicCONJUGATE
symphysis (PS)
•• Measured
Line drawn
midpoint1.2cm
of
by from
subtracting
(True
Conjugate)
SP
midpointconjugate.
of PS
fromtodiagonal
• Smallest and most important
DIAGONAL
CONJUGATE:12cm
diameter
•• Line
drawnbyfrom
midpoint of
Measured
subtracting
SP to lowerfrom
border
of PS
1.5-2cm
diagonal
• conjugate
It is measured clinically
during pelvic assessment in
late pregnancy or in labor.

8.

TRANSVERSE DIAMETER
PELVIC INLET
DIAMETERS
This is the greatest distance
between
the linea terminal
on either side. It measures
about 13cm
OBLIQUE DIAMETER
• There are two oblique
diameters-right and left.
• Each one extends from one
sacroiliac joint to the
opposite iliopubic eminence
and measures 12 cm .
• Right or left denotes the

9.

BOUNDARIES
PELVIC CAVITY
• The pelvic cavity lies between the pelvic inlet and
pelvic outlet.
•Anterior wall:
•Formed by the pubic bone
•Shallow
•Posterior wall:
•Formed by the sacrum
•Deep and concave
• Contains two important planes:
1.Plane of greatest pelvic dimension
2.Plane of least pelvic dimension (Midpelvis)

10.

PELVIC CAVITY
PLANE
PLANEOFOFTHE
THE LEAST
1.2.PLANE
PELVIC DIMENSION
GREATEST
PELVIC
(MIDPELVIS)
DIMENSION
•Has obstetrical significance.
•Passes through:
• The midpelvis is the plane of least
•Junction of S2–S3 vertebrae
pelvic dimension and the narrowest
•Laterally
thefetus
ischialmust
bones,
middle
of the
regionover
the
pass
through.
It has three important diameters.
acetabulum
•Posterior surface of the symphysis pubis
•Shape: Nearly circular
Diameter
Anteroposterior
Transverse
Measurement
12.5 cm
12.75 cm

11.

DIAMETER OF
MID PELVIS
PELVIC
CAVITY
Diameter
Description
Normal Value
Transverse
(Interspinous)
Diameter
Distance between the
two ischial spines;
smallest diameter of
the pelvis
10 cm
Anteroposterior
Diameter
From the lower border
of the pubic
symphysis to the
junction of the 4th
and 5th sacral
vertebrae
11.5 cm
Posterior Sagittal
Diameter
From the midpoint of
the interischial
diameter to the
junction of the 4th
6 cm

12.

BOUNDARIES
PELVIC OUTLET
Shape of the Pelvic Outlet
•The pelvic outlet is irregular in
outline
•It roughly resembles two triangles in
different planes
•The bases of the triangles meet at the
line of the interischial spine
Direction
Posterior
Lateral
Boundary
Tip of the coccyx
Ischial tuberosities
Anterior
Pubic arch formed by the
inferior rami of the

13.

DIAMETERS
PELVIC OUTLET
1. Anteroposterior Diameter
•Distance: Inferior border of the symphysis pubis →
posterior aspect of the tip of the sacrum
•Measurement: 12 cm
2. Transverse Diameter
•Distance between the inner edges of the ischial
tuberosities
•Measurement: 10.5–11 cm
3. Posterior Sagittal Diameter
•Distance: Midpoint of the transverse diameter → tip

14.

TYPES OF
PELVIS
:Caldwell and Moloy’s
classification
On the basis of shape of the inlet, female
pelvis is
divided into four types
1. Gynecoid-50%
2. Anthropoid-25%
3. Android -20%
4. Platypelloid-5%

15.

TYPES OF
PELVIS

16.

TYPES OF
PELVIS

17.

THE FETAL
SKULL
The fetal skull consists of three parts:
1.Vault
1.The most important part in labour
2.Compressible → allows moulding
3.Bones forming the vault:
1.2 frontal bones
2.2 parietal bones
3.1 occipital bone
4.2 temporal bones
5.Wings of sphenoid
2.Base of the Skull
1.Bones are firmly united → noncompressible
3.Face

18.

THE FETAL
SKULL
SUTURES
Sutures are membranous gaps between
fetal skull bones.
They allow overlapping (moulding)
during labour.
Major Sutures :
•Frontal suture → between two frontal
bones
•Sagittal suture → between two
parietal bones
•Coronal sutures → between frontal &
parietal bones
•Lambdoidal sutures → between parietal
bones & occipital bone
•Temporal sutures → between parietal

19.

FONTANELLES
THE FETAL
SKULL
Fontanelle
Anterior
(Bregma)
Posterior
Shape &
Location
Lozenge/diamo
nd-shaped; at
junction of
sagittal &
coronal
sutures
Bones Forming
It
2 parietal
bones
(posterior),
2 frontal
bones
(anterior)
Small,
triangular;
at junction
of sagittal &
lambdoidal
sutures
2 parietal
bones +
occipital
bone
Sutures Felt
Sagittal,
coronal,
frontal
Sagittal &
lambdoidal

20.

FETAL SKULL
DIAMETERS
TRANSVERSE
DIAMETERS
Biparietal Diameter – 9.5 cm
•Max distance between parietal
eminences
•Largest transverse diameter
•Engagement = BPD reaches the
pelvic brim
Bitemporal Diameter – 8 cm
•Between two temporal bones
•Smallest diameter of fetal
skull

21.

FETAL SKULL
DIAMETERS
ENGAGING
DIAMETERS
• When the fetal head enters the pelvic
brim, one of the AP diameters aligns with
the transverse or oblique pelvic
diameters.
• The choice of engaging diameter depends
on the type of cephalic presentation:
• Vertex (OA / OP)
• Face presentation
• Brow presentation

22.

FETAL SKULL
DIAMETERS
ANTEROPOSTERIOR
(AP) DIAMETERS
1. Suboccipito-bregmatic Diameter – 9.5
cm
•Anterior fontanelle → just below
occipital protuberance
•Engaging diameter in occipitoanterior
(OA) vertex presentation
•Head circumference: 27.5 cm
•MOST favourable for labour
2. Submento-bregmatic Diameter – 9.5 cm
•Chin–neck junction → anterior
fontanelle
•Engaging diameter in face
presentation

23.

FETAL SKULL
DIAMETERS
ANTEROPOSTERIOR
(AP) DIAMETERS
3. OCCIPITOFRONTAL DIAMETER – 11 cm
•Root of nose (glabella) →
occipital protuberance
•Engaging diameter in deflexed
occipitoposterior (OP) position
•Circumference: 34 cm
4. SUBOCCIPITO-FRONTAL DIAMETER –
10.5 cm
•Below occiput → frontal bone
•Sometimes engages in OP position

24.

ANTEROPOSTERIOR
(AP) DIAMETERS
FETAL SKULL
DIAMETERS
5. VERTICOMENTAL (MENTOVERTICAL)
DIAMETER – 13 cm
•Chin tip → farthest point of vertex
•Largest skull diameter
•Engaging diameter in brow
presentation
•Circumference: 37.5 cm
•Labour usually obstructed → CS often
required

25.

Measurement
Description
Engaging
Diameter In
Head
Circumference
9.5 cm
Anterior
fontanelle →
below occipital
protuberance
Occipitoanterior
(Vertex OA)
27.5 cm
9.5 cm
Chin–neck
junction →
anterior
fontanelle
Face
presentation
—
11 cm
Glabella →
occipital
protuberance
Occipitoposterio
r (deflexed
head)
34 cm
Suboccipitofrontal (SOF)
10.5 cm
Below occiput →
frontal bone
Alternate
engaging
diameter in OP
—
Verticomental /
Mentovertical
(VM)
Diameter
Chin tip →
13 cm (largest)
highest point of
vertex
Measurement
Brow
presentation
37.5 cm
Diameter
Suboccipitobregmatic (SOB)
Submentobregmatic (SMB)
Occipitofrontal
(OF)
Biparietal diameter (BPD)
9.5 cm
Importance
Largest transverse
diameter, must pass
pelvic brim for
engagement

26.

REFERENCE:
MUDALIAR CLINICAL
OBSTETRICS