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for molding of fetal head to occur – molding helps maneuver through maternal birth canaloFetal head smooth & round optimal shape to apply pressure to cervix & aid in dilation 4 types :oVERTEX fetal head fully flexed – most frequent & optimaloMILITARY head presents in neutral position – occipitofronal diameter presentsin pelvis & top of head is presentingoBROW head partially extended – unstable presentation that converts to vertex if head flexes or face presentation if extendsOccipitomental diameter presents in pelvis & sinciput presenting oFACE head is extended & occiput near fetal spineSubmentobregmatic presents to pelvis & face presentingBREECH PRESENTATION butt enters maternal pelvic 1stClassified according to attitude of fetal hips & knees – more likely in preterm or presenceof fetal abnormalityoAlso associated with abnormalities in maternal uterus or pelvisMany factors can compromise normal labor – usually do CS
Disadvantages of breech:oInc risk for umbilical cord prolapse bc presenting part may not be covering cervixoPresenting part (butt/feet) is not as smooth & hard as fetal head & less effective in dilating cervixoOnce fetal body (abdomen) is delivered umbilical cord can become compressed –fetus must then be delivered expeditiously to prevent hypoxia situation allows no time for molding 3 types: frank, complete (full), footlingFRANK common, fetal legs completely extended up toward fetal shoulder – hips are flexed, knees are extended, fetal butt present in maternal pelvis COMPLETE same as flexed position but with butt presenting 1stoLegs typically flexed- reversal to common cephalic FOOTLING one or both legs are extended with one (single) or both feet (double) presenting 1stinto maternal pelvis SHOULDER PRESENTATIONTransverse lie – rare most likely require CSWhen present, maternal abdomen appears large from side to side& demonstrate lower than expected fundal height measurement Shoulder usually presenting part but arm, back, abdomen, or side can be tooMost often occur in preterm births, high partiy, premature rupture membrane, hydramnios, placenta previa-Passageway + Passenger and their Relationship (engagement, attitude, position)oRelationship btwn maternal pelvis and fetus and membranes assessed when determining engagement, station, & fetal position oEngagement occur when widest diameter of fetal presenting part passed through pelvic inletCephalic- largest diameter is biparietalBreech – largest diameter is intertrochanteric diameter Can be determined by external palpation or vag examPrimigravidas – occurs approx. 2 wks before due dateMultiparas – may occur many wks before onset of laborConfirms adequacy of pelvic inlet oStation level of presenting part in relation to maternal ischial spinesIschial spines represent narrowest diameter through which fetus must pass