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Flashcards in Maternal Pelvis Deck (46)
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Describe the android pelvis

- Triangular/ heart-shaped with narrow forepelvis
- Prominent ischial spines with convergent side walls
- Transverse diameter situated at bacl
- Sacrum is straight
- Deep cavity
- Sacro-sciatic notch is narrow
- Pubic arch = <90 degrees


Describe the anthropoid pelvis

- Long oval brim with narrow forepelvis
- AP diameters longer than transverse
- Side walls divergent
- Sacrum long and concave
- Ischial spines not prominent and blunt
- Sub-pubic angle = >90 degrees
- Common in women of African descent


What percentage of pelves are anthropoid?



What percentage of pelves are platypelloid?



Describe the platypelloid pelvis

- Flat, female-type pelvis
- Kidney-shaped brim with wide forepelvis
- Side walls divergent
- All AP diameters short
- Transverse diameters long
- Sacrosciatic notch narrow
- Sub-pubic angle = >90 degrees
- Sacrum flat and cavity shallow
- Ischial spines not prominent and blunt


What are the 3 conjugate diameters?

1. True/ Anatomical Conjugate
2. True/ Obstetric Conjugate
3. Diagonal Conjugate


Describe the anatomical conjugate

- Sacral promontory to upper part of SP
- 12cm


Describe the obstetric conjugate

- Upper posterior border of SP to sacral promontory
- 11cm
- Represents available space for passage of foetal head through pelvis


Describe the diagonal conjugate

- Lower border of SP to sacral promontory
- 12-13cm
- Not measured in the UK


What is asynclitism?

- Lateral tilting of the head
- Allows biparietal diameter to pass narrowest AP diameter of brim


Describe anterior asynclitism

- Anterior parietal bones move down behind the SP until the parietal eminence enters the brim
- Movement is then reversed and head tilts in opposite direction until posterior parietal bone negotiates sacral promontory and head is engaged


Describe posterior asynclitism

- Anterior synclitism in reverse
- Posterior parietal bone negotiates sacral promontory prior to anterior parietal bone moving behind SP
- Once pelvic brim has been negotiated, descent progresses normally accompanied by flexion and internal rotation


Give a condition of the pelvis that arises from dietary deficiency

- Rachitic Pelvis
- Pelvis is deformed by rickets in childhood due to malnutrition; weight of upper body presses down on pelvis, causing bow legs and spinal deformity
- Sacral promontory pushed down and forward and ilium and ischium drawn outwards, resulting in flat pelvic brim
- Woman usually has CS due to asynclitism


Give a condition of the pelvis that arises from developmental anomaly

- Naegele's Pelvis
- 1 sacral ala missing
- Sacrum is fused to the ilium, causing a grossly asymmetric brim
- Head cannot engage


Give a condition of the pelvis that arises from injury and disease

- Trauma
- Fractured pelvis will develop a callus/ fail to unite
- Reduce measurement and some degree of contraction


What happens to the coccyx during labour?

Pushed back