Fetal skull and maternal pelvis Flashcards
What is the gynaecoid pelvis
Normal female 50%
The brim is a transverse ellipse
Side walls are straight with blunt ischial spines
Subpubic angle 90-100
What is the anthropoid pelvis
Apelike 25%
The brim is an A.P. ellipse
What is an android pelvis
20% - male type
Inlet is triangular or heart-shaped with anterior narrow apex.
Side walls are converging (funnel pelvis) with projecting ischial spines
Subpubis angle of <90
What is a platypelloid pelvis
5%
A.P. diameters are short while transverse diameters are long
Subpubic angle is wide.
What are the 4 anterior-posterior diameters
1* Anatomical antero-posterior diameter (true conjugate) = from the tip of the sacral promontory to the upper border of the symphysis pubis = 11cm
2* Obstetric conjugate = from the tip of the sacral promontory to the most posterior part of pubic symphysis = 10.5 cm
3* Diagonal conjugate - from the tip of sacral promontory to the lower border of pubic symphysis = 12.5cm
4* AP of Outlet - From coccyx to the lower border of the symphysis pubis = 13.5cm
What are the 2 transverse diameters
1* Anatomical transverse diameter - 13cm - between the farthest two points on the iliopectineal lines
2* Obstetric transverse diameter - slightly shorter than the anatomical transverse diameter
Which diameters come with
1) Flexed vertex position
2) Partially deflex vertex postion
3) Deflexed vertex position
1) Suboccipito-bregmatic diameter 9.5cm (junction of occipital bone and neck to bregma)
2) Suboccipito-frontal diameter 10.5cm (junction of occipital bone and neck to mid frontal bone)
3) occipito-frontal diamter 11.5cm (most prominant point of frontal bone to most prominent point on occipital bone
Which diameters come with brow presentation?
Mento-vertical diameter 13.5cm (chin to furthest point on vertex). Incompatible with delivery
Which diameter comes with face presentation?
Submento-bregmatic diameter 9.5cm (junction of chin and neck to the bregma)
What is the biparietal diameter
9.5cm
