PROBLEMS OF PASSAGEWAY Flashcards
● Inlet - Heart shaped, funnel shaped
● Midpelvis
○ Midpelvic diameters reduced
○ Sacrosciatic notch narrow
○ Symphysis is long
○ Pelvic cavity is deep
● Outlet
○ Narrow suprapubic angle
○ Lateral walls tend to converge
○ Short transverse diameter of the outlet
ANDROID PELVIS
● Most common pelvic cause of difficult labor
● Not favorable to vaginal birth
● Descent into pelvis is low
ANDROID PELVIS
● Inlet
○ Short anteroposterior and wide
transverse diameter
○ Shape of inlet is a narrow transverse
ellipse, with the widest diameter about
equidistant from the symphysis pubis
and promontory
○ Short AP diameters, both AP relatively
shallow
● Midpelvis
○ Capacity is reduced
● Outlet
○ Capacity may be inadequate
PLATYPELLOID PELVIS
● Fetal head engages in transverse position in marked
asynclitism
● Difficult descent through midpelvis
● Frequent delay of progress at outlet of pelvis
PLATYPELLOID PELVIS
● Inlet
○ AP diameter of the inlet is long, whereas
the transverse is relatively or absolutely
shortened
○ Shape of the superior aperture is that of
a longitudinal ellipse
● Midpelvis
○ Widest transverse diameter is
considerably in front of the promontory,
the posterior segment is deep
○ Sacrosciatic notch is wide, sacrum is
more or less vertical and often contains
six segments
ANTHROPOID PELVIS
● Fetal head enters the pelvis obliquely and is
posterior more frequently than anterior
● Arrest of the posteriorly placed occiput at the outlet
and delivery as a persistent occipito-posterior
occasionally occur
ANTHROPOID PELVIS
CA contracture (narrowed diameter) in any of the
described areas can result in CPD if fetus is larger
than the pelvic diameters
CEPHALOPELVIC DISPROPORTION
● Pelvic inlet bis contracted if the shortest AP is <10
cm or the greatest TD is <12 cm
● AP diameter may be approximated by measuring
the DC, which in the contracted inlet is 11.5 cm
CONTRACTED INLET
● Generally contracted pelvis is the most common
type of pelvic deformity
● Usually found in small-bones, undersized women
● Android and platypelloid types are predisposed to
CPD
CONTRACTED PELVIS
● Inter-ischial tuberous diameter of <8 cm constitutes
an outlet contracture
● Outlet and midpelvic contractures frequently occur
simultaneously
CONTRACTURES OF THE OUTLET
● Is applied to contraction of plane of least
dimensions, and implies that either the TD or AP
diameter or both, are reduced in size
● Transverse contraction is associated with the
anthropoid type of the pelvis, and AP contraction
with the platypelloid type
CONTRACTURES OF THE MID-PLANE
● May result from narrowness of the upper part of the
sacrosciatic notch, from a straight sacrum, or from
one that is inclined forward
TRANSVERSE CONTRACTION
