This document describes the structure of the female pelvis and its relation to childbirth. The pelvis is comprised of four bones - the two innominate bones, the sacrum, and the coccyx. It has several diameters that must accommodate the fetus during labor and delivery, including the anteroposterior, oblique, and transverse diameters. There are also four types of pelvises - gynecoid, anthropoid, android, and platypeloid - that can impact the birthing process. The pelvis, its joints, ligaments, and diameters are all designed to allow the fetus to pass through the birth canal during labor.

1. FEMALE PELVIS IN RELATION TO
CHILD BIRTH
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SESSION 3

2. Related tasks
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I. Describe the structure of the female
pelvis(bones,ligaments,joints)
II. Identify types of pelvis
III. Describe pelvis diameters and landmarks
IV. Draw and label female pelvis

3. THE FEMALE PELVIS
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 The female pelvis is the bonny compartment which
supports the vertebrae column, and its articulation
with the lower limbs, it permits a person to sit and
kneel.
 It forms a bonny passage through which the fetus
passes during labour.
 It comprises of four bones
 Two innominate or unnamed bones
 One sacrum
 One coccyx

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7. INNOMINATE BONES
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• Is made up of three bones: Illium, Ischium and the
Pubis
• The illium
• Is the large flared-out part; when the hand is placed
on the hip it rests on the iliac crest, which is the
upper border. At the front of the iliac crest can be felt
a bony prominence known as the anterior superior
iliac spine.

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• Below is the anterior inferior iliac spine. There are
two similar points at the other end of the crest,
posterior superior and posterior inferior iliac spines.
• The ischium
• Is the thick lower part which has a large prominence
known as the ischial tuberosity, on which the body
rests when sitting. Behind and a little above the
tuberosity is an inward projection known as, the
ischial spine. During labor the station of the fetal
head is estimated In relation to the ischial spines.

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The pubic bone
 This bone forms the anterior part. It has a body and
two oar-like projections, the superior ramus and the
inferior ramus. The two pubic bones meet at the
symphisis pubis and the two inferior rami form the
pubic arch, merging into a similar ramus on the
ischium. The space enclosed by the body of the pubic
bone, the rami and the ischium is called the
obturator foramen.

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 The ischium contains a deep cup to receive the head
of femur, called acetabulum. On the lower boarder of
the innominate bone are found two curves. One
extends from the posterior inferior iliac spine up to
the ischial spine and is called greater sciatic notch.
The other lies between the ischial spine and ischial
tuberosity and is the lesser sciatic notch.

11. THE SACRUM
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• The sacrum is a wedge-shaped bone consisting of
five fused vertebrae. The upper border of the first
sacral vertebra juts forward and is known as sacral
promontory.
• The anterior surface of the sacrum is concave and is
referred to as the hollow of the sacrum. Laterally the
sacrum extends into a wing or ala. Four pairs of
holes or foramina pierce the sacrum and, through
these, nerves from the cauda equina emerge to
supply the pelvic organs. The posterior surface is
roughened to receive attachment of muscles

12. THE COCCYX
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 Is a vestigial tail which consist of four fussed
vertebral forming a small triangular bone. The
coccyx articulates with the fifth sacral vertebra to
form the sacrococcygeal joint. During birth the
coccyx is usually forced backwards to allow more
room for the fetus to pass.

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Pelvic joints
• There are four pelvic joints;
• One symphisis pubis
• Two sacro iliac joints
• One sacrococcygeal joint.
• The pelvic joints are not very mobile in non
pregnant woman, but during pregnancy the
endocrine activity causes the ligaments of the joints
to soften which allows the joints to soften and
stretch during labour

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The symphisis pubis
 It is formed at the junction of the two pubic bones,
which are united by a pad of cartilage. It widens
during the last months of pregnancy and, because of
its increased mobility may cause the pregnant
woman pain as she walks.

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Sacroiliac joints
 These are the strongest joint in the body. They join
the sacrum to the ilium and thus connect the spine to
the pelvis. During pregnancy much stress is placed
on these joints and multipara often complain of
backache during pregnancy and for few weeks
following delivery.

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Sacrococcygeal joint
 This joint is formed where the base of the coccyx
articulates with the tip of the sacrum. The joint
allows the coccyx to move backwards during birth,
thus widening the outlet of the pelvis.

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pelvic ligaments
Each of the pelvic joints is held together by ligaments;
 Interpubic ligaments at the symphysis pubis
 Sacroiliac ligament,
 Sacrococcygeal ligaments.

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 The other two ligaments important in midwifery
are:-
 Sacrotuberous ligaments :- from the sacrum to the
ischial tuberosity
 Sacrospinous ligament: - from the sacrum to the
ischial spine.

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The pelvic floor
 The pelvic floor is formed by the soft tissues that fill the
outlet of the pelvis.
Functions
 The pelvic floor supports the weight of the abdominal
and pelvic organs.
 Its muscles are responsible for the voluntary control of
micturation and defecation and play an important role in
sexual intercourse.
 During child birth it allows the passive movements of
the fetus through the birth canal

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Muscle layers
 The superficial layer which is composed of five
muscles:-
 The external anal sphincter encircles the anus and is
attached behind by a few fibers to the coccyx
 The transverse perineal muscles pass from the ischial
tuberosity to the centre of the perineum.

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 The bulbocavernosus muscles pass from the
perineum forward around the vagina to the copra
cavernosa of the clitoris just under the pubic arch.
 The ischial cavernosa muscles pass from the ischial
tuberosities along the pubic arch to the copra
cavernosa.
 The membranous sphincter of the urethra is
composed of muscle fibres passing above and below
the urethra and attached to the pubic bone.

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The deep layer
This layer is composed of three pairs of muscles which
together re known as levator ani muscles. Each
levator ani muscle (left and right) consist of the
following:
 The pubococcygeus muscle from the pubis to the
coccyx
 The iliococcygeal muscle from the fascia covering the
obturator intenus muscle to the coccyx
 The ischiococcygeus muscle from the ischial spine to
the coccyx

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25. DIAMETERS OF PELVIS
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The true pelvis
• It is the bonny canal through which the fetus must
pass during birth. It has a brim, cavity and outlet
The pelvic brim
• The brim is round except where the sacral
promontory projects into it. The promontory and
wings of sacrum form its posterior boarder, the iliac
bones its lateral boarders and the pubic bone its
anterior boarder

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The land marks of the brim are:
 Sacral promontory
 Sacral ala or wing
 Sacro iliac joint
 Iliopectineal line
 Iliopectineal eminence

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 Superior ramus of the pubic bone
 Upper inner boarder of the body of pubic bone
 Upper inner boarder of the symphysis pubis
Diameters of the brim
 Three diameters are measured

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The anteroposterior diameter
• It is a line from the sacral promontory to the upper
boarder of the symphysis pubis. When the line is
taken to the upper boarder of the symphysis pubis it
is called the anatomical conjugate and is measured
12 cm; When it is taken to the posterior boarder of
the upper surface 1.25 cm lower is called obstetrical
conjugate and measures 11 cm, it represent the
available space for the passage of the fetus.

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 The diagonal conjugate is measured from the lower
boarder of the symphysis pubis to the sacral
promontory it may be estimated on vaginal
examination as part of pelvic assessment and should
measure 12-13 cm.

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The Oblique diameter
 It is a line from one sacroiliac joint to the
iliopectineal eminence on the opposite side and
measures 12 cm. There are two diameters left and
right oblique diameters each takes its name from the
sacroiliac joint from which it arises.

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The transverse diameter
• It is a line between the points further apart on the
iliopectineal line and measures 13 cm.
• Another diameter is measured, the sacrocotyloid
diameter from the sacral promontory to the
iliopectineal eminence on each side and measures 9-
9.5 cm. It is only important in posterior positions of
the occiput.

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The pelvic cavity
• The cavity extends from the brim above to the cavity
below. The anterior wall is formed by the pubic bone
and the symphysis pubis and is 4 cm long. The
posterior wall is formed by the curve of sacrum and
is 12 cm long. Its lateral walls are the sides of the
pelvis
• The cavity is circular in shape its diameters cannot
be measured but are considered to be 12 cm.

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The outlet
• Two outlets are described, the anatomical and
obstetrical. The anatomical outlet is formed by the
lower border of the pelvic bones and the
sacrotuberous ligaments.
• The obstetrical outlet is the space between the
narrow pelvic strait and the anatomical outlet. The
narrow pelvis strait lies between the sacrococcygeal
joint, the two ischial spines and the lower boarder of
symphysis pubis. There are three diameters;-

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The anteroposterior diameter
• It is a line from the lower boarder of the symphysis
pubis to the sacrococcygeal joint. It measures 13 cm.
the coccyx may be deflected backwards during
labour. The dimeter indicates the space available
during delivery.
The oblique diameter
• Between the obturator foramen and the sacrospinous
ligaments there are no fixed points the measurement
is taken to be 12 cm.

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The transverse diameter
 This is a line between the two ischial spines and
measuers 10-11 cm it is the narrowest diameter in the
pelvis.

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The false pelvis
 The false pelvis is the part situated above the brim. It
is formed by the upper flared-out part of the iliac
bones and protects the abdominal organs.

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39. TYPES OF PELVIS
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There are four types of pelvis
 Pelvises are classified according to shape of the brim.
Much important is the individual woman’s pelvic
capacity and whether it is adequate for the passage of
the child she is carrying.

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Gynaecoid pelvis
 It is the ideal pelvis for child bearing
 Its main features are rounded brim, straight side
walls, and shallow cavity with broad well curved
sacrum, blunt ischial spines, wide sciatic notch and a
pubic arch of 90 degrees.
 It is found in women with average size and height
with shoe size of 4 or larger.

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 All diameters are reduced but are in proportion. It is
normally found in women of small stature less than
1.5 m in height with small hands and feet.

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The android pelvis
• It resembles the male pelvis. Its brim is heart shaped
with a narrow fore pelvis. It is a funnel shape with a
deep cavity and straight sacrum. The ischial spines
are prominent and the sciatic notch is straight. The
sub pubic angle is less than 90 degrees, it is found in
heavily built women
• The heart shaped brim favors posterior position of
the occiput and is the least suited for child bearing.

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The anthropoid pelvis
 It has a long oval brim in which the anteroposterior
diameter is long than the transverse. The sacrum is
long and deeply concave. The ischial spines are not
prominent, the sciatic notch and sub pubic angle are
very wide. It is found in women who are tall with
narrow shoulders. Labour does not usually present
any difficulties.

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The Platypeloid Pelvis
 This flat pelvis has a kidney-shaped brim in which
anteroposterior diameter is reduced and the
transverse increased. The sacrum is straight and the
cavity is shallow.
 The ischial spines are blunt and the sciatic notch
and sub pubic angle are wide.
 The head must engage with the sagittal suture in the
transverse diameter but usually descends without
difficulty

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