Female Pelvis & Fetal diameters

A-P diameters

Inlet
true conjugate- 11 cms
obstetric conjugate- 10-10.5
diagonal conjugate- 12

Mid -11.5 cms
Outlet -11.5-13.5 cms

Oblique diameter @ inlet -12 cm

Transverse diameter

Inlet-13-13.5cms
Mid Pelvis-interspinous diameter-10cm
Outlet-intertuberous diameter-11cm

Ischial spine:
1.Plane of ischial spine-plane of least pelvic dimensions
2.Internal rotation
3.beginning of forward curve of pelvic axis
4.most cases of deep transverse arrest occur here
5.level of external os
6.represents zero station of fetal head
7.Corresponds to origin of levator ani
8.landmark of pudendal block
 9.ischial spine separates greater sciatic notch from lesser sciatic notch
10.external surface gives attachment to the Gemellus superior
11.internal surface gives attachment to the Coccygeus, Levator ani, and the pelvic fascia
12.pointed extremity the sacrospinous ligament is attached.


Pelvic inlet- sacral promontory,alae sacrum,linea terminalis (lateral), pubic symphysis(anteriorly)
Pelvic brim-promontory,arcuate line of ilium,pectineal lineof pubis, pubic crest

Posterior Saggital diameter-7.5cms
prognosis of vaginal delivery in case of narrowing of mid pelvis depends on it

Fetal diameters:

Transverse-Miss Tina So Pretty
Bimastoid-7.5cm
Bitemporal-8cm
Super subparietal-8.5cm
Biparietal-9.5cm


AP diameters

1. suboccipito-bregmatic -9.5cm- vertex-complete flexion
2.subccipito-frontal-10cm vertex-incomplete flexion
3.occipito-frontal-11.5cm vertex-marked deflexion
4.mento-vertical-14cm-partial extension
5.submento-vertical-11.5cm-incomplete extension
6.submento-bregmatic-9.5cm-complete extension

longest diameter of fetal skull-mentovertical-14cm
longest diameter of pelvis- transverse@inlet AP@anatomic outlet
shortest diameter of pelvis-posterior saggital@outlet
shortest diameter of inlet sacrocotyloid
longest AP diameter of inlet-diagonal conjugate
shortest AP diameter of inlet-obstetric conjugate
only AP diameter measured clinically diagonal conjugate