1. THE BONY PELVIS

2. THE BONY PELVIS a. Pelvic anatomy b. Pelvic joints
c. Planes & diameters of the pelvis
d. Pelvic shapes
e. Pelvic size and its clinical estimation

3. a. PELVIC ANATOMY
b. PELVIC JOINTS
- Symphysis pubis
- Sacroiliac joints
- Relaxation of the pelvic joints
( especially during pregnancy)

8. ( Has no obstetrical significance , it is not considered further)
PLANES AND DIAMETER OF THE PELVIS
HAVING 4 IMAGINARY PLANES :
1. The plane of the pelvic inlet ( Superior strait )
2. The plane of the pelvic outlet ( Inferior strait )
3. The plane of the mid pelvis ( least pelvic dimensions )
4. The plane of greatest pelvic dimensions
( Has no obstetrical significance , it is not considered further)

12. HODGE PLANE I = Pelvic inlet
II Hodge I through lower margin of the symphysis
III Hodge I through ischial spine
IV Hodge I through the tip of coccygis

14. Android pelvis Anthropoid pelvis Platypelloid pelvis PELVIC SHAPES
CALDWELL - MOLOY CLASSIFICATION ( )
Gynecoid pelvis
Android pelvis
Anthropoid pelvis
Platypelloid pelvis

15. GYNECOID PELVIS ANDROID PELVIS
- Almost 50% of white women (Todd’ Collection study)
- Ascertained the frequency of the four parent pelvic types
by study of Todd’s Collection ( Caldwell & CoWorkers,1939)
ANDROID PELVIS
- 1/3 of pure type pelvis ( white women), 1/6 non white women
- The extreme android pelvis presages poor prognosis for vaginal
delivery
- The frequency of difficult forceps operations increases

16. INTERMEDIATE TYPE PELVIS
ANTHROPOID PELVIS
- 1/4 pure type pelvis in white women and nearly
1 1/2 of those in non white women
PLATYPELLOID PELVIS
- Rarest of the pure varieties ( < 3% )
INTERMEDIATE TYPE PELVIS
- Mixed type
- More frequent than pure types

17. CALDWELL MOLOY

18. PELVIC SIZE AND ITS CLINICAL ESTIMATION
- Pelvic inlet measurements
- Diagonal conjugate
- Engagerment : - with engagerment, the fetal head
serves as an internal pelvimeter to demonstrate
that the pelvic inlet is ample for that fetus.

19. PELVIC INLET
- Obstetrical conjugate ( normal > 10 cm)
- Diagonal conjugate
CD to 2 cm = True conjugate

26. PELVIC OUTLET MEASUREMENTS
( diameter between the ischial tuberosities )
Called as :
- Biischial diameter , Inter tuberous diameter, Transverse
diameter of the outlet
- The shape of the sub pubic arch also can be evaluated
at the same time by palpating the pubic rami from the
sub pubic region toward the ischial tuberosities.
- Estimated by placing a closed fist against the
perineum between the ischial tuberosities, after fist
measuring the width of the closed fist ( usually > 8 cm )

27. MID PELVIS ESTIMATION
- Clinical estimation of mid pelvis capacity by any direct form of measurement is not possible -
Suspicion contracted pelvis in this region :
- Ischial spines are quite prominent
- The side walls are felt to converge
- The concavity of the sacrum is very shallow
- Ischial diameter of the outlet < 8 cm

28. Outer measurement
Distantia spinarum
Distantia cristarum
External conjugate (Baudelaque)
Vaginal examination

30. 95 % of all labors is in vertex presentation and most commonly ascertained by abdominal palpation and confirmed by vaginal examination
Majority of cases the vertex enters the pelvis with the sagittal suture in the transverse pelvic diameter
The fetus enters the pelvis in the Left Occiput Transverse Position / LOT (40% of labors) & 20% ROT.
The head either enters the pelvis with the occiput rotated 45o anteriorly from the transverse position

31. 20 % of all labors the fetus enters the pelvis in an Occiput Posterior (OP) position.
The ROP is slightly more common than LOP and posterior positions are more often associated with a narrow forepelvis
The head either enters the pelvis with the occiput rotated 45o anteriorly from the transverse position

32. THE CARDINAL MOVEMENTS OF LABOR ARE :
ENGAGEMENT
DESCENT
FLEXION
INTERNAL ROTATION
EXTENSION
EXTERNAL ROTATION
EXPULSION

33. ENGAGEMENT
The biparietal diameter, the greatest transverse diameter of the fetal head in occiput presentations, passes through the pelvic inlet is designated engagement (during the last few weeks of pregnancy)
A normal – sized head usually does not engage with its sagittal suture directed anteroposteriorly.
Instead, the fetal head usually enters the pelvic inlet either in the transverse diameter or in one of the oblique diameters.

34. ASYNCLITISM
Although the fetal heads tends to accommodate to the transverse axis of the pelvic inlet, the sagittal suture , while remaining parallel to that axis, may not lie exactly midway between the symphysis and sacral promontory
The sagittal suture frequently is deflected either posteriorly toward the promontory or anteriorly toward the symphysis.
Such lateral deflection of the head to a more anterior or posterior position in the pelvis is called asynclitism
Moderate degrees of asynclitism are the rule in normal labor, but if severe , may lead to CPD

35. DESCENT
In nulliparas, engagement may take place before the onset of labor and further descent may not follow until the onset of second stage. In multiparous women, descent usually begins with engagement.
Descent is brought about by one or more of four forces :
Pressure of the amniotic fluid
Direct pressure of the fundus upon the breech with
contractions
Bearing down efforts with the abdominal muscles
Extensions and straightening of the fetal body