Content is helpful to the students those who are doing masters in Obstetrics and Gynecological nursing.

1. SUBMITTED TO: PRESENTED BY:
Mrs. Anugrah Milton Komal Upreti
Head Of Department M.Sc. Nursing
Obstetrics & Gynaecological Nursing First Year
RAK College Of Nursing
DISSCUSSION
ON
FETAL SKULL

2. INTRODUCTION
• Understanding the anatomy of the fetal skull and its diameter will help you
recognise how a labour is progressing, and whether the baby's head is
'presenting' correctly as it comes down the birth canal. This will give you a
better understanding of whether a normal vaginal delivery is likely, or if
the mother needs referral because the descent of the baby's head is not &
making sufficient progress.
 The fetal head is large in relation to the fetal body compared with the
adult.
 The fetal skull is the most difficult part of the baby to pass through the
mother's pelvic canal, due to the hard bony nature of the skull. Adaptation
between the fetal skull and the pelvis is necessary to allow the head to
pass through the pelvis during labour without complications.

3. OBJECTIVES
 Define the fetal skull.
 Enumerate the importance of fetal skull.
 Describe the divisions and regions of the fetal skull.
 Enlist the bones which constitute the fetal head.
 Elaborate the sutures and fontanelles in fetal skull and their importance.
 Describe the various diameters and circumferences of the fetal skull and their
significance.
 Discuss the moulding and its relevance.
 Identify types of injury that can occur to the fetal skull during labour and birth.

4. DEFINITION OF FETAL SKULL
• Fetal skull is the part of fetal body which encase and protect
the brain.
• Skull is compressible to some extent because it made up of
thin flat bones which forms the vault. This is anchored to
the rigid and incompressible bones at the base of the skull.

5. IMPORTANCE OF FETAL SKULL
1. Largest part of the fetal body.
2. Most frequent presenting part of the fetus during
delivery.
3. Least compressible among all the fetal parts.

6. DIVISONS OF FETAL SKULL
The fetal skull has divided into 3 major parts:
• VAULT: The vault is the large, dome-shaped part above an
imaginary line drawn between the orbital ridges and the
nape of the neck.
• BASE: The base comprises bones that are firmly united to
protect the vital centres in the medulla oblongata.
• FACE: The face is composed of 14 small bones that are also
firmly united and non-compressible.

7. REGIONS OF FETAL SKULL
VERTEX
• It is a quadrangular area bounded anteriorly by the
bregma and coronal sutures behind the lambda and
lambdoid sutures and laterally by lines passing
through the parietal eminences.
BROW
• It is an area bounded on one side by the anterior
fontanelle and coronal sutures and on the other side
by the root of the nose and the supra orbital ridges
of the either side. The base comprises bones that
are firmly united to protect the vital centres in the
medulla oblongata.

8. FACE
• It is the area bounded on one side by root of the nose
and supra orbital ridges and on the other, by the
junction of the floor of the mouth and neck. The
point between the eyebrows is known as glabella.
SINCIPUT
• It is the area lying in front of the anterior fontanelle
and corresponds to the area of brow.
OCCIPUT
• It is the area limited to the occipital lobe.
REGIONS OF FETAL SKULL

9. BONES OF FETAL HEAD
Fetal head is consists of 7 bones:
 2 Frontal bone
 2 Parietal bone
 2 Temporal bone
 1 Occipital bone

10. SUTURES AND ITS TYPES
1.Sagittal or longitudinal suture
2.Lies between two parietal bones
1.Coronal suture
2.Between parietal and frontal
bones on either side
1.Frontal suture
2.Lies between two frontal bones
1.Lambdoid suture
2.Separate the occipital bone and
the two parietal bones.
SUTURES

11. IMPORTANCE OF SUTURES
It permits gliding
movement of one bone
over the other during
moulding of the head, a
phenomenon of
significance while the
head passes through
the pelvis during
labour.
Digital palpation of
sagittal suture during
internal examination in
labour gives an idea of
the manner of
engagement of the
head, degree of internal
rotation of the head
and degree of moulding
of the head.

12. FONTANELLES AND ITS TYPES
POSTERIOR
FONTANELLE
• The posterior fontanelle or lambda is
situated at the junction of the lambdoidal
and sagittal sutures.
• Triangular in shape.
• Closes at 6 weeks of age
ANTERIOR
FONTANELLE
• The anterior fontanelle or bregma is
found at the junction of the sagittal,
coronal and frontal sutures.
• Diamond in shape.
• Closes at 18 months of age.

13. IMPORTANCE
OF
FONTANELLE
It facilitates
moulding of the
head.
Its palpation
during internal
examination
denotes the
degree of flexion
of the head.
Palpation of the
floor reflects
intracranial
status.
Cerebrospinal
fluid can be
drawn, although
rarely from the
lateral ventricle.
It helps in
accommodating
the marked
brain growth.
Denotes the
position of head
in relation to
maternal pelvis.

14.  Sub-mento bregmatic (SMB)
 Measured from the point where the chin joins the neck to the centre of the bregma.
 9.5cm in diameter.
 Sub-occipito bregmatic (SOB)
 Extends from the nape of the neck to the centre of the bregma.
 9.5cm in diameter.
 Occipitofrontal (OF)
 Measured from the occipital eminence to the glabella.
 11.5cm in diameter.
 Sub-mento vertical (SMV)
 Measured from the point where the chin joins the neck to the highest point on the vertex.
 11.5cm in diameter.
D
I
A
M
E
T
E
R
S
O
F
S
K
U
L
L
 Sub-occipitofrontal (SOF)
 Extends from the nape of the neck to the anterior end of the anterior fontanelle or the centre of the
sinciput.
 10cm in diameter.
 Mento vertical (MV)
 Measured from the point of the chin to the highest point on the sagittal suture.
 14cm in diameter.

15. D
I
A
M
E
T
E
R
S
O
F
S
K
U
L
L
 Biparietal diameter
 Extends between two parietal eminences. Whatever may be the position of the head, the diameter
nearly always engages.
 9.5cm in diameter.
 Bitemporal diameter
 It is the distance between the antero-inferior ends of the coronal suture.
 8.2cm in diameter.
 Super- subparietal diameter
 It extends from a point placed below one parietal eminence to a point placed above the other
parietal eminence of the opposite side.
 8.5cm in diameter.
 Bimastoid diameter
 It is the distance between the tips of mastoid process.
 7.5cm in diameter.

16. CIRCUMFERENCES
Circumference of the plane of the diameter of engagement differs according to the attitude of the
head.
ATTITUDE OF THE
HEAD
PLANE OF
ENGAGEMENT
SHAPE CIRCUMFERENCE
Complete Flexion Biparietal sub
occpito bregmatic
Almost round 27.5cm
Deflexed Biparietal sub
occpito frontal
Oval 34cm
Incomplete extension Biparietal mento
vertical
Bigger oval 37.5cm
Complete extension Biparietal sub mento
bregmatic
Almost round 27.5cm
.

18.  The overlapping of the fetal skull bones at the suture line.
(Wylie, 2005, p.201)
 It is the alteration of the shape of the fore-coming head while passing through the resistant
birth passage during labour.
(D C Dutta,2013,p.86)
Bones of vault allow slight bending and override one another at the sutures.
Skull changes shape from ovoid to cylindrical.
Causes presenting diameter to decrease while increasing the diameter at right angles.
MOULDING

19. MECHANISM OF
MOULDING:
• There is compression of the
engaging diameter of the head
with corresponding elongation
of the diameter at right angle to
it.
• Thus, in well flexed head of the
anterior vertex presentation, the
engaging suboccipito bregmatic
diameter is compressed with
elongation of the head in
mento-vertical diameter which
is at right angle to suboccipito
bregmatic.
IMPORTANCE OF MOULDING:
 Slight moulding is good and
beneficial because it enables the
head to pass more easily, through
the birth canal.
 Shape of the moulding can be a
useful information about the
position of the head occupied in
the pelvis.

20. GRADING
• There are three gradings:-
• Grade-1—the bones
touching but not
overlapping.
• Grade-2— overlapping but
easily separated.
• Grade-3—fixed
overlapping.

21. INJURIES DURING THE DELIVERY OF HEAD
CAPUT SUCCEDANEUM
• Oedematous swelling that occurs on the
presenting part.
• Present at birth.
• Can cross over the sutures.
• Soft swelling and will indent with
pressure.
• Decreases following delivery.
• No treatment is required.
• Will disappear approximately 24-48hrs
after birth.
• Moulding will also be apparent.

22. INJURIES DURING THE DELIVERY OF HEAD
CEPHALOHEMATOMA
 Bleeding that occurs between the
bones of the fetal skull and
periosteum.
 Occurs 12-72 hours after birth.
 The swelling is restricted to one area
and will not indent with pressure.
 Does not cross over the sutures.
 Can be bilateral.
 Persist for a few weeks and
occasionally months.

23. BIBLIOGRAPHY
Burden, B. and Sapsed, M.S., The Fetal Skull. In: Macdonald, S.,Magill-Cuerden (eds.) Mayes'
Midwifery 14th ed. London: Ballière Tindall, 2011, page no: 96-104.
 Wylie, L., Essential anatomy and physiology in maternity care. 2nd ed. Edinburgh:
Elsevier,2005,page no: 201-206.
 Shirish S Sheth, Essential of Obstetrics, 1st Edition, Jaypee Brothers Medical Publishers, New
Delhi,2004, page no.: 102 - 104.
 Diane M, Myles Textbook for Midwives, 14th edition, Elsevier Publisher, London, 2008, page no:
118-123.
 Dutta D C, Textbook of obstetrics,7th edition, New central book agency (P) ltd. ,London ,2013,
page no: 83-87.
 Shirish N Daftary, Manual of obstetrics,2nd edition, Elsevier publication, 2007, Page no: 68-72.