Female pelvis, pelvic inlet, outlet,midpelvis, greatest pelvic dimensions,,waste space of Morris, Caldwell Moloy classification, naegele's pelvis, Robert's pelvis , subpubic angle,Gynaecoid pelvis, Android pelvis, anthropoid pelvis, platypelloid pelvis, Sacrosciatic notch, interspinous diameter, inter tuberous diameter

1. Anatomy of Female Pelvis

2. Female pelvis
• Pelvis may be divided by the linea terminalis into 2 parts
1. Upper part- pelvis major or false pelvis- no Obstetric significance
2. Lower part- pelvis minor or true pelvis
• Linea terminalis-
• upper border of Sacral vertebrae,
• arcuate line of ilium and
• pectineal line of pubis.

3. True pelvis
• True pelvis lies below and behind the linea terminals.
• Walls of true pelvis are partly bony and partly ligamentous
• Boundaries-
• Above- Promontory And alae of sacrum, linea terminalis, upper margin of
pubic bones
• Below- pelvic outlet
• Posterior- anterior surface of sacrum
• Laterally- inner surface of ischial bones,sacrosciatic notches and ligaments
• Anterior- pubic bones, ascending superior rami of ischial bones,obturator
foramina

5. Pelvic cavity
• Cylindrical in shape
• Extends from pelvic brim or inlet from above to outlet below
• Posterior wall( 10cm)is deeper than anterior wall(5cm)
• In erect posture,
• Upper part of the cavity – downwards and backwards
• Lower part – downward and forwards- curve of Carus

7. Pelvic musculature
• Boundaries-
• Sides- pyriformis
• Posterior- coccygeus muscle
• Lateral- obturator internus
• Inferior- levator ani
• Pelvic diaphragm- musculoaponeurotic part separating the pelvis
above from the perineum and vulva below.
• Formed by levator ani and coccygeus
• 3 orifices- urinary meatus, vulval outlet, anus.

9. Planes and Diameters of the Pelvis
• In true pelvis, diameters are taken at different planes.
• Plane of Pelvic inlet ( superior strait)
• Plane of pelvic outlet ( inferior strait)
• Plane of least pelvic dimensions ( midpelvis)
• Plane of greatest pelvic dimensions ( no obstetrical significance)

11. Pelvic inlet
• Boundaries-
• Posterior- sacral Promontory and alae of sacrum
• Lateral – linea terminalis
• Anterior- Horizontal rami of pubic bones and pubic symphysis
• 3 Diameters
• Anteroposterior diameter
• Transverse diameter
• Oblique diameter

13. Anteroposterior diameter of inlet
• Anatomical conjugate or true conjugate ( 11cm) - distance between
sacral Promontory and upper portion of inner surface of pubic
symphysis.
• Obstetrical conjugate ( 10cm)- between sacral Promontory nad
nearest point on posterior surface of pubic symphysis.
1. Shortest diameter through which the presenting part of the fetus
must pass at the time of delivery.
2. It is indirectly measured by using diagonal conjugate.

15. AP diameter of inlet
• Diagonal conjugate (11.5-12cm)- sacral Promontory to apex of pubic
arch.
• Clinically measurable,
• Obstetrical conjugate is calculated by subtracting 1.5- 2cm from the
diagonal conjugate, depending on the thickness of pubic arch.

17. Transverse diameter of inlet
• Greatest distance between the linea terminalis on either side.
• Measures about 13.5 cm
• It intersects the diagonal conjugate at a point, 4cm in front of the
Promontory
• Segment posterior to the intersection- Posterior sagittal diameter of
inlet- it facilitates the descent of fetal head

19. Oblique diameter of inlet
• Extends from sacroiliac joint on one side to ilio pectineal eminence on
other side.
• Right oblique diameter- right sacroiliac joint to ilio pectineal
eminence on left side
• Left oblique diameter- left sacroiliac joint to ilio pectineal eminence
on right side.
• Measures about 13cm

20. Pelvic outlet
• Irregular in outline, resembles 2 triangles in different planes with
their bases meeting at the line of inter-ischial spine.
• Boundaries-
• Posterior- tip of the coccyx.
• Lateral- ischial tuberosity
• Anterior- pubic arch( formed by inferior rami of ischium and pubis as
they converge towards pubic symphysis)

22. Diameters of pelvic outlet
• 3 diameters
• Anteroposterior diameter( 9.5 – 11.5cm)- inferior border of pubic
symphysis to posterior aspect of tip of scrum.
• Transverse diameter (11cm)- between the inner edges of ischial
tuberosities.
• Posterior sagittal diameter of outlet (7.5cm) – from the midpoint of
line between ischial tuberoisties and external surface of the tip of the
sacrum.

25. Plane of least pelvic dimensions ( Midpelvis)
• Boundaries-
• Anterior- lower margin of pubic symphysis
• Lateral- ischial spines
• Posterior- tip of the sacrum.
• 3 diameters
• Anteroposterior diameter (11.5cm) – midsymphysis to fused S2,S3
• Transverse or interspinous diameter (10cm)- between the base of ischial
spines. Smallest diameter of pelvis.
• Posterior sagittal diameter (4.5cm)- midpoint of the line between the
ischial spines and sacrum.

29. Plane of greatest pelvic dimensions
• No obstetrical significance
• Boundaries-
• Posterior-junction of S2 ,S3,
• Lateral- ischial spines over the middle of acetabulum.
• 2 diameter
• Anteroposterior diameter (12.5cm)
• Transverse diameter (12.75cm)

31. Planes and diameters of pelvis
Diameters Pelvic inlet Pelvic outlet Least pelvic
dimensions
Greatest pelvic
dimensions
AP diameter True conjugate-
11cm
Obst. conjugate-
10cm
Diagonal conjugate-
11.5-12cm
9.5- 11.5 cm 11.5cm 12.5 cm
Transverse diameter 13.5cm 11cm 10cm 12.75cm
Oblique diameter 13cm - - -
Posterior sagittal
diameter
4cm 7.5cm 4.5cm

32. Waste space of Morris
• Normally, the distance between the pubic symphysis and the edge of
round disc diameter 9.3cm( approximately fetal head ) placed under
sub pubic arch.
• Normally, the subpubic angle is well rounded and the distance
between the pubic symphysis and edge of the disc should not be
more than 1cm.
• If it is more than 1cm, AP diameter of outlet is reduced.

33. Waste space of Morris

34. Caldwell and Moloy’s classification
• Morphological classification of pelvis.
• Intermediate or Mixed type of Pelvis
• Most common
• Type of pelvis can be determined by posterior segment, while
anterior segment determines the tendency.
• Eg- pelvis with gyneacoid posterior segment with android type of
anterior segment- gynecoid pelvis with android tendency

36. Caldwell and Moloy’s classification
Gynecoid pelvis Android pelvis Anthropoid pelvis Platypelloid pelvis
Shape Heart shaped Funnel shaped Anteroposteriorly oval Transversely oval
Inlet
• TD vs AP
• PSD vs ASD
• Sides of posterior
segment-
• >/=
• </=
• Wide / well rounded
• < , restricts the
posterior space
• Not rounded,
• anterior pelvis-
narrow, triangular
<
Anterior segment-
narrow, pointed
>>
Wide , flat
Midpelvis
• Sidewalls
• Spines
• TD
• Straight
• Not prominent
• >/= 10cm
• Convergent
• Prominent
Convergent
Prominent
Straight
Outlet
• Pubic arch Wide Narrow Narrow, well shaped Very wide
Sacrum
• Inclination
• Sacrosciatic notch
• Neither anterior nor
posterior
• well rounded, never
narrow
Straight +/- curvature
• Narrow ,highly
arched
Straight
Large
Average
Narrow

40. Clinical significance
Gynecoid pelvis Android pelvis Anthropoid pelvis Platypelloid pelvis
Small gynecoid pelvis
• Proportionately
reduced diameter,
with normal shape
• Delay at every stage of
labour
• Occipito posterior
position- m/c
• Incomplete rotation
• Deep transverse arrest
Persistent Occipito
posterior position
Difficulty in engagement
of fetal head

41. Abnormalities of pelvis
Rachitic flat pelvis Nagele’s pelvis Robert’s pelvis Kyphoscoliosis
Rickets Arrested development of
one alae of sacrum
Arrested development of
both alae of sacrum
Tuberculosis
Rickets

42. Rachitic type of pelvis

43. Naegele’s pelvis vs Robert’s pelvis