1. Fetal Skull
Badeea Seliem Soliman Assistant Prof. of gynecology and obstetrics Zagazig university

2. Fetal Skull Vault – Face – Base
The vault is composed of soft bones separated by sutures and fontanelles.

3. Vault is subdivided into
Forehead
Vertex
Occiput

4. 1) Forehead
From Bregma
to root of the
nose.

5. Bounded: (2) Vertex It is an area of the vault of skull Anteriorly
anterior fontanelle
Posteriorly
posterior fontanelle
Laterally
line passing through
parietal eminence

6. 3) Occiput From posterior fontanelle to the external occipital
Protuberance.

7. Bones of the vault IS (7 bones) 2 frontal bones 2 parietal bones 2 temporal bones 1 occipital bone
The bones of the vault are not joined thus changes in the shape of the fetal head during labor can occur due to moulding

8. Sutures (number = 6) Spaces between skull bones.
Made of un-ossified membranes which allows movements of cranial bones to decrease the skull diameters.

9. Sutures = 6 in number - Sagittal suture - Frontal suture
- Coronal suture
Lambdoidal sutures
2 Temporal sutures

10. Fontanels : Areas where sutures meet 6 in numbers

11. 2 anterior temporal fontanelles at the junction of temporal and coronal sutures
2 Posterior temporal
fontanelles
at the junction of
temporal &lambdoidal
sutures
no obstetric importance.

12. Anterior fontanelle
Posterior fontanelle
obstetric importance.

13. Posterior fontanelle (Lambda) Anterior fontanelle (Bregma)
Small -
Lozenge shaped - Large
Obliterated at FT
Obliterated at 1.5y after birth
Formed by meeting of 3 bones
Connected to 3 sutures
- Formed by meeting of 4 bone
- Connected to 4 sutures
Bony floor
Soft membranous floor
With moulding of the head, over-riding of surrounding bones one parietal bond-­overrides the other and both override the occipital bone
With moulding —> no over-riding of bones as they are widely separated
from the start

14. Obstetric importance of ant. & post. Fontanelle
1- Diagnosis of vertex presentation 2- Detection of the position of the occiput (anterior or posterior or lateral) 3- Detection of the degree of flexion or deflexion of the head.

15. FETAL SKULL DEFINITIONS
Bregma  Ant fontanelle
Brow  lies between Bregma &root of the
nose
Face  lies between root of the nose &
subra orbital ridges and chin
Occiput boney prominence behind post
fontanelle
Vertex Diamond shaped area between ant & post fontanelles & parietal eminences

16. FETAL SKULL SUTURES Frontal suture  between 2 frontal bones
Sagittal suture  between 2 parietal bones
Coronal suture  between parietal & frontal
Lambdoid suture  between parietal & occipital
Temporal suture  between inferior margin of
the parietal & temporal bones

17. FETAL SKULL FONTANELLES
Anterior fontanelle 
Diamond shaped space between coronal & sagittal suture - ossifies at 18 m
Posterior fontanelle (lambda) 
Triangle shaped space between sagital
suture & Lambdoidal suture

18. Diameters of Fetal Skull

19. Diameters of fetal skull
Longitudinal
(6)
Transverse
(4)

20. Longitudinal Diameters (6)

21. 1- Suboccipito bregmatic (9.5 cm)
From sub occipital point
to center of anterior fontanelle
The diameter of engagement
in occipito anterior position
when head is completely flexed

22. 2- Suboccipito - frontal (10 cm)
From sub occipital point to
anterior end of Bregma.
1- Diameter of engagement
in vertex presentation with mild deflexion of the head.
2- Diameter that distends the vulva in occipito anterior if the head is allowed to extend after crowning.

23. Importance: 3- Occipito -frontal (11.5 cm):
From the occipital protuberance to the root of the nose.
Importance:
-Diameter of engagement
in O.P.
2- The diameter that distends the vulva in face to pubis delivery with O.P.
3-The diameter that distends the vulva if the head extends before crowning in O A.

24. 4- Sub mento- bregmatic (9.5 cm)
From the junction of the neck and chin to the centre of the bregma.
Importance:
It is the engaging diameter in face presentation with completely extended head.

25. 5- Sub mento -vertical (11.5 cm)
From the junction of the neck and chin to the vertical point (a point on the sagittal suture midway between the anterior and posterior fontanelles)
1- Diameter of engagement
in face presentation with the head incompletely extended.
2- Diameter that distends the
vulva in face delivery (m.a.).

26. 6- Mento- vertical (13.5-14 cm):
From the tip of the chin
to the vertical point.
Importance:
It is the diameter facing the pelvic brim in brow presentation.
It is more than the largest diameter of the pelvic brim

27. Longitudinal Diameters (6)
Suboccipito bregmatic (9.5 cm)
Suboccipito -frontal (10 cm)
Occipito -frontal (11.5 cm)
Sub mento- bregmatic (9.5 cm
Sub mento -vertical (11.5 cm)
Mento-vertical ( cm)

28. Q: What is the name of diameter number 3 – 4 – 5?

29. Transverse diameters
(4)

30. Interesting, right?
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