Dystocia Second part: abnormalities of birth canal

Pelvic contraction 4 Birth canal – bony canal –soft canal 4 abnormal bony canal: pelvic contraction –any contraction of the pelvic diameters that diminishes the capacity of the pelvis can creat dystocia during labor

Classification 4 Contraction of the pelvic inlet 4 contraction of the midpelvis and pelvic outlet 4 general contraction of the pelvis 4 pelvic deformities

Contracted pelvic inlet 4 Anteroposterior d<10cm 4 diagonal conjugate d<11.5cm 4 external conjugate d<18cm –simple flat pelvis –rickets flat pelvis

Contracted midpelvis 4 Midpelvis: from inferior margin of the symphysis pubis through the ischial spines,touches the sacrum near the junction of the 4th and 5th vertebrae 4 contraction: interischial spinous diameter is smaller than 8cm(spines are prominent, the pelvic side walls converge or the sacrosciatic notch is narrow)

Contracted pelvic outlet 4 Defination: diminition of the interischial tuberous diameter to 8cm or less. 4 2 triangles: –baseof both: interischial tuberous diameter –anterior triangle –posterior triangle

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Outlet contraction without concomitant midplane contraction is rare 4 Funnel shaped pelvis 4 transversely contracted pelvis

General contraction of the pelvis 2cm or more shorter than normal Pelvic deformities osteomalacic pelvis obliquely contracted pelvis

Effects on mather and fetus 4 MOTHER:Inlet –Malpresentation and malposition –prolonged labor –insufficient uterine contraction 4 midpelvis and outlet –persistant occipitotransverse or occipitoposterior position –fistula formation –intrapartum infection –threatening rupture or rupture

fetus 4 PROM 4 Prolapse 4 Distress (HI,IVH) 4 Death 4 Injury 4 Infecion

Soft birth canal 4 Lower segment of uterus 4 cervix 4 vaginal

Fetal malposition 4 Occipitoanterior position 90% 4 malposition 10% abnormal cephalic posion 6-7% breech presentation 3-4% others

Persistant occipitoposterior (transverse) position 4 Causes –abnormal pelvis:transverse narrowing of the midpelvis –flexion not well –hypotonic uterine dysfunction

Breech presentation 4 Incidence –breech presentation is common remote from term. –3-4% of singleton deliveries 4 Position –LSA, LST LSP. RSA, RST, RAP

Causes 4 Uterine relaxation 4 limited uterine cavity 4 fetal head obstructed

classification 4 Frank breech p –the lower extremities are flexed at the hips and extended at the knees, and thus the feet lie in close proximity to the head. –It appears most commonly 4 complete breech p –differs in that one or both knees are flexed. 4 Incomplete breech p –one or both hips are not flexed and one or both feet or knees lie below the breech, that is, a foot or knee is lowermost in the birth canal.

Incomplete breech presentation

Effects 4 Maternal –greater frequency of operative delivery –higher maternal morbidity and slightly higher mortality –PROM –secondary hypotonic uterine dysfunction –puerperium infection –postpartum haemorrhage –laceration of cervix

Effects 4 Fetus –PROM –cord prolapse –fetal distress even death –newborn asphyxia –brachial plexus injury –IVH

Face presentation

Compound presentation