for graduate and undergraduate students

1. FETAL SKULL
By: Maj Saminder Malik
MSc (N) Obs & Gyn

2. INTRODUCTION
Contains delicate brain to prevent any pressure as head passes
through birth canal
Large in comparison to fetal body and maternal pelvis
Require adaptation between fetal skull & maternal true pelvis
Most difficult part to deliver
Somewhat compressible and made of pliable tubular bones
forming vault

4. BONES OF SKULL
Total 05 bones in skull
1. Occipital bone (1): at the back of head, at the center of it has
occipital protuberance
2. Parietal Bones (2):at the either side of head, ossification center
of each is Parietal eminence
3. frontal Bones (2): forms the forehead, center of each is known
as frontal eminence. Frontal bones fuses into single by 8 yrs. of
age

6. SUTURES OF THE SKULL
1. LAMBDOID: shape like Greek letter Lambda, separates
occipital bone from two Parietal bones
2. SAGITTAL: longitudinal suture, lies between two parietal bones
3. CORONAL: separates frontal bones from parietal bones
4. FRONTAL: lies between two frontal bones

8. AREAS OF SKULL
1. VAULT: large dome shaped wall above an imaginary line drawn
between the orbital ridges and the nape of neck
2. BASE: comprised of bones which are firmly united to protect the vital
centers in the medulla
3. BROW: extends from anterior fontanels and coronal sutures to the
orbital ridges
4. FACE: bounded on one side by the root of nose and supraorbital
ridges & other side by the junction of the floor of mouth with neck.
(composed of 4small bones, firmly united & compressible)

9. FONTANELLES
1. ANTERIOR (BREGMA):
2. POSTERIOR( LAMBDA)

10. ANTERIOR FONTANEL (BREGMA)
anteriorly frontal suture, posteriorly sagittal suture and laterally
coronal suture
Diamond shaped
Measures 3-4cm long & 1.5 – 2cm wide
Closes by 18months (1.5yrs)
Pulsations can be felt through it
Help in molding of head, assessing position of head during labor,
depressed during dehydration, bulging during increased ICP,
collection of CSF from lateral angles

11. POSTERIOR FONTANEL (LAMBDA)
Formed by anteriorly sagittal suture and laterally lambdoid suture
Triangular in shape
Measures 1.2 ˣ 1.2
Floor is membranous
Closes by 6weeks (1.5 months)
Helps in assessing position and degree of flexion of head of
head

13. LANDMARKS
1. BREGMA: anterior fontanel
2. LAMBDA: posterior fontanel
3. VERTEX: bounded anteriorly by Bregma, posteriorly by Lambda
and laterally by parietal eminence. Quadrangular in area,
considered as a presenting part in labor.
4. BROW: bounded superiorly by bregma & coronal sutures and
inferiorly by root of nose & supraorbital ridges.
5. GLABELLA: point between two eyebrows
6. FACE: bounded superiorly by root of nose and supraorbital ridges
and inferiorly by the junction of floor of mouth with neck
7. SINCIPUT: area in front of bregma, lined by frontal bone
8. OCCIPUT: between foramen magnum & lambda, lined to occipital
bone
9. MENTUM: chin

14. DIAMETERS OF SKULL
1. ANTEROPOSTERIOR/ LONGITUDINAL
2. TRANSVERSE

16. AP /LONGITUDINAL DIAMETERS
AP Diameter Extension Clinical
Importance
SUBOCCIPITOBREGMATIC From below the occipital protuberance to
center of bregma, 9.5cm
Complete flexion
vertex
SUBOCCIPIATOFRONTAL From below the occipital protuberance to
center of frontal suture, 10cm
Partial flexion
vertex
OCCIPITOFRONTAL From occipital protuberance to the glabella,
11.5cm
Deflexion
vertex
MENTOVERTICAL From midpoint of chin to highest point on
vertex, 14cm
Partial extension
brow
SUBMENTOBREGMATIC From junction of floor of mouth & neck to
center of bregma, 11.5cm
Complete
extension, face
SUBMENTOVERTICAL From junction of floor of mouth & neck to
highest point of vertex, 9.5 cm
Partial extension
face

18. TRANSVERSE DIAMETERS
Transverse Diameter Extension
BIPARIETAL Between two parietal eminences, 8.5cm
BITEMPORAL Between two coronal sutures, 8cm
BIMASTOID Between tips of mastoid process, 7.5cm

19. CLINICAL CONDITIONS
MOLDING OF HEAD
CAPUT SUCCEDANEUM
CEPHALHEMATOMA

21. MOLDING OF HEAD
Occurs with descent of fetal head into pelvis to reduce head
circumference
Obliteration of sutures
Overlapping of the bones of vault (frontal bones slip under parietal
bones, parietal bones override each other, parietal bones slip under
occipital bones)
Reduces the fetal skull diameters by 0.5 -1cm or even more
Degree:
0 (suture lines separate)
+1 (suture lines meet)
+2 (suture lines overlap but can be reduced by gentle digital
pressure
+3 (suture lines overlap irreducible)

23. CAPUT SUCCEDANEUM
Diffuse scalp edema resulting from venous congestion due to
prolonged pressure on fetal head by the pelvic bones
Soft & boggy to touch
Disappears after birth
Mostly localized in nature
Usually few mm thick but may be large
Medico-legal implication: baby was living, difficult labor

24. CEPHALHEMATOMA
Swelling due to bleeding between skull bone & periosteum
Bleeding occurs due to friction between overriding bones and
periosteum during molding
Likely to occur during difficult vaginal labor
Low prothrombin levels can be contributory
Not present at birth but appears after 2-3 days
Swelling is limited by periosteum, so doesn't cross the suture line
Head appears more red & bruised
Swelling can increase & may take 6weeks to disappear