Undergraduate course lectures in obstetrics and gynecology prepared by DR Manal Behery,prof of obstetrics&Gynecology

1. Bony pelvis and fetal skull
Dr Manal Behery
2014

2. Objects
Fetal head
Pelvic anatomy
Pelvic shapes

4. Fetal head
Landmarks
Sutures
Fontanelles
Diameters

5. Fetal head
From an obstetrical point of view it’s the most
important part:
largest
least compressible part of the fetus.
most frequent presenting part

7. Landmarks
Head is divided into 3areas
(1) the sinciput or brow portion;
(2) the vertex, or top of the head between the 2
fontanelles;
(3) Base large, ossified, firmly united, and
noncompressible

8. Sutures
Membrane-occupied spaces between the cranial
bones
1-Sagittal suture:
- lies btw the parietal bones
-extends in an AP direction btw the fontanelles
-divides the head into right and left sides

9. 2-lambdoid suture:
extends from the posterior fontanelle laterally
separate the occipital from the parietal bones.

10. 3-coronal suture:
extends from the anterior fontanelle laterally
separate the parietal and frontal bones.

11. 4- frontal suture:
lies between the frontal bones
extends from the anterior fontanelle to the
glabella (the prominence between the
eyebrows).

12. Clinical importance of sutures
Position of fontanelle & sagittal suture can identify attitude and
position of vertex.
By plapating the sagittal suture during labour, degree of internal
rotation & molding of the head can be noticed.
In deep transverse arrest, this sagittal suture lies transversely at
the level of the ischial spines.

14. Moulding…
Reshaping of the fetal skull:
Obliteration of the sutures.
Overlapping of the bones of the
vault:
One parietal bone overlaps the
other.
Both overlap the occipital
bone.
It accounts for diminution of
the biparietal diameter and
suboccipitobregmatic
diameters by 0.5-1 cm. 0r
even more.

15. A: Well flexed Head
B: Partially Flexed Head
C: Deflexed Head
D: Face Presentation
E: Brow presentation

16. The anterior fontanelle (bregma) :
diamond shaped area(2 × 3 cm) of
unossified membrane formed by
the junction of 4 suture.

17. The posterior fontanelle:
 It is the triangular depressed area at the
junction of 3 suture:
closes at 6 to 8 weeks of life
Y- or T-shaped

18. ROT LOT

19. LOAROA

20. LOP
RO
P
LOP

23. Transverse Diameters of the Fetal
Skull
Biparietal Diameter 9.5 cm Between the 2 parietal
eminences
Bitemporal Diameter 8.5 cm.
Bimastoid Diameter 7.5 cm. Between the 2 mastoid
processes (Not reducible
nor destroyable even by
destructive procedures
Supra-subparietal 8.25 - 9 cm. Asynclitic head

25. presenting AP diameter when the head
is deflexed >>> OP

26. -presenting AP diameter in a brow presentation
-longest AP diameter of the head

27. -4. Submentobregmatic (9.5 cm):
presenting AP diameter in face presentations

28. Length Presentation
1-Suboccipito-bregmatic 9.5 cm. Flexed vertex
2-Suboccipito-frontal 10.5 cm. Partially deflexed vertex
3-Occipito-frontal 11.5 cm. Deflexed vertex
4-Mento-vertical 13.75-14 cm. Brow
5-Submento-bregmatic 9.5 cm. Face
6

30. Engaging Diameters of Fetal Skull
Well Flexed Head Circle of 9.5 cm.
The engaging Diameter is the
Suboccipito-Bregmatic diameter
A deflexed Head An oval
The longer occipito-frontal
diameter Of 11.5 cm. Is exposed.
Greater Deflexion
of the Head
An oval
The longer mento vertical
diameter of 13.75-14 cm. is
exposed
Full Extension of
the Head
A circle of 9.5 cm.
The engaging dimeter is the
submento-vertical diameter

31. Female bonyFemale bony
pelvispelvis

32. False Pelvis
bordered by:
lumbar vertebrae posteriorly
iliac fossa bilaterally
abdominal wall anteriorly.
supports the abdominal contents
after 1st
trimester helps support the gravid
uterus.

34. Pelvic outlet

35. Ischial Tuberosity Ischial Spine
SP

38. The Planes of the pelvis
Plane of the pelvic inlet.
Plane of the cavity: Plane of greatest Pelvic Dimensions
Plane of the mid pelvis (plane of obstetric outlet)
Plane of the Anatomical outlet

39. (Inlet (Pelvic brim)
passing with the
boundaries of
pelvic brim and
making an angle of
55o with the
horizon (angle of
pelvic inclination).

40. Pelvic inclination:
The plane of the
pelvic inlet makes
an angle of 55
degree with the
horizon in the
standing position"

41. The consequences of walking upright…
When a women stands erect:
The pelvic inlet makes an angle of about 55° with the horizon.
The pelvic outlet makes an angle of 15° with the horizon
If the angle made by the inlet is greater than 55° this may make
the descent of the fetal head in the pelvis difficult.

42. Diameters of the pelvic
inlet

43. The True Conjugate = 11 cm
The Obstet. Conjugate = 10.5cm
The Diagonal Conjugate = 12 cm

44. (4) External conjugate:
From: The upper anterior
margin of the symphysis pubis.
To: The depression below the
tip of the 5th lumbar spine
(20 cm).

45. (5) Anatomical transverse diameter:
Between the farthest points on iliopectineal lines (= 13 cm).
It lies 4 cm infornt of the sacral promontory, 7 cm behind
the symphysis pubis.
(6) Obstetric
transverse
diameter:
It bisects the
true
conjugate
(12.5 cm)
ATD
OTD
TC

46. (7) The oblique
diameters: (12 cm)
The right extends from the
right joint to the left
eminence and vice versa.
(8) Sacrocotyloid
diameter: (9-9.5 cm)
The right diameter ends in
the right eminence & vice
versa.

47. The pelvic Cavity
Boundaries:
Above: pelvic brim.
Below: plane of least pelvic
dimensions.
Anteriorly: syrnphysis
pubis.
Posteriorly: sacrum.

48. bordered by:
the posterior midpoint of the pubis anteriorly
the upper part of the obturator foramina laterally
the junction of the 2nd and 3rd sacral vertebrae posteriorly.
The fetal head rotates to the anterior position in
this plane
2- pelvic cavity The plane of greatest
diameter:

49. The pelvic Outlet
(A)Anatomical outlet: Lozenge
-shaped, bounded by:
Lower border of symphysis
pubis.
Pubic arch.
Ischial tuberosities
Sacrotuberous & sacrospinous
ligaments.
Tip of the coccyx.

50. The Plane of the Outlet
Anterior Sagittal Plane
Posterior Sagittal Plane

51. Diameters of the pelvic outlet
(1)Anteroposterior
Anatomical anteroposterior
(11 cm)
b Obstetric anteroposterior
(13 cm)

52. (2) Transverse diameters
Bituberous (11 cm), between the inner aspects of
ischial tuberosities
Bispinous (10.5 cm), between the tips of ischial
spines.
Diameters of the pelvic outlet

53. Interspinous diam. = 10.5 cm.
Obstet. Ant. Post diam= 13 cm.
Anato. Ant. Post diam= 11 cm.

54. (3) Anterior sagittal
diameter = 6-7 cm
.
(4) Posterior sagittal
diameter = 7-10 cm
Diameters of the pelvic outlet

55. Diameter Inlet Cavity outlet
Anteroposterior diameter 11 12.5 13
Transverse diameter 13 12.5 11
Diameters of the pelvic

56. The pelvic axis:
Anatomical axis
(Curve of Carus):

57. The Obstetric Pelvic Axis
This represents the
path that the
presenting part must
follow for delivery to
occur:
The upper part moves
downward
approximately in a
straight line till the level
of the ischial spine.
The trajectory then
changes to become a
curvilinear path directed
forward and downward

58. The Fetal Head Has Five Fifths…
0 : Head Not Palpable
1 : Sinciput felt – Occiput Not Felt
2 : Sinciput felt – Occiput Just Felt
3 : Sinciput easily felt – Occiput
Felt
4 : Sinciput High – Occiput easily
Felt
5 : Complete above pelvic brim
fifthabove
-5
0
+5

59. Pelvic Shapes

60. Gynecoid Pelvis
The classic female type.
Found in approximately 50% of women.
Characteristics:

61. Android Pelvis
The typical male type
Found in less than 30% of women
Characteristics:
1. Triangular inlet with a flat

62. Anthropoid Pelvis
Resembles ape pelvis.
Found in approximately 20% of women
Characteristics:
,

63. Platypelloid Pelvis
Flattened gynecoid pelvis.
Found in only 3% of women