MECHANISMOFLABOUR(NORMAL&ABNORMAL)PresentedByDr.ZEINABABOTALIBMRCOG,DGO,AssociateProfessor&ConsultantObs/GynaInfertility&IVFLie,presentation,attitude,&positionFETALLIETherelationofthelongaxisofthefetustothatofthemotherLongitudinallieisfoundin99%oflaboursattermPredisposingfactorsfortransverselie/obliquelie

multiparity,placentaprevia,hydramnious,&uterineanomaliesFETALPRESENTATIONThepresentingpartistheportionofthebodyofthefetusthatisforemostinthebirthcanalThepresentingpartcanbefeltthroughtheCxonvaginalexaminationLongitudinalliecephalicpresentationbreechpresentationTransvrselieshoulderpresentation

Lie,presentation,attitude,&positionCEPHALICPRESENTATIONHeadisflexedsharplyvertex/occiputpresentationHeadisextendedsharplyfacepresentationPartiallyflexedbregmapresenting(sinciputpresentation)PartiallyextendedbrowpresentationBREECHPRESENTATIONFrankbreechCompletebreechFootlingbreechATTITUDEPostureofthefetusfoldedonitselftoaccommodatetheshapeoftheuterusFlexedhead,thighs,knees&feetThearmscrossedoverthechestFacepresentationextendedconcavecontourofthevertebralcolumn.'"'I!1\11ABii FcD

Longitudinallie.Ce-phalicpresentation.Differencesinattitudeoffetalbody,

Notechangesinfetalattitudeinrelationtofetalvertexasthefetalheadbecomeslessflexed.(A)vertex(B)sinciput(C)brow(D)face

Longitudinallie.Frankbreechpresentation.II

Longitudinallie.Completebreechpresentation.

Longitudinallie.Incomplete,orfootling,breechpresentation.POSITIONTherelationofanarbitrarychosenpointofthefetalpresentingparttotheRtorLtsideofthematernalbirthcanalThechosenpointVertexpresentation

occiputFacepresentationmentumBreechpresentationSacrumEachpresentationhastwopositionsRtorLtEachpositionhas3varieties:Ant,transverse,postOAOPLOTROTLOAROALOPROP~'tJLONGITUDINALLIEVERTEXPRESENTATIONLOALOPs

A

Longitudinallie.VertexpresentationA.Rightocciputposterior(ROP)Rightocciputtransverse(ROT)Sfa!wCchtp(fittb

fewcalta

tb

oj

Rightocciputanterior(ROA).FREQUENCYOFVARIOUSPRESENTATIONS&POSITIONSATTERMVertex96%2/3

Lt1/3

RtBreech

3.5%Face

0.3%Shoulder

0.4%

Longitudinallie.Facepresentation.Leftandrightanteriorandposteriorpositions.Rt

mento-postRt

mento-antLtmento-ant~LongitudinallieBreechpresentationLSP

Transverselie.Rightacromiodorsoposteriorposition(RADP).Theshoulderofthefetusistothemother'sright,andthebackisposterior.MECHANISMOFLABOURWITHOCCIPUTPRESENTATIONS

THECARDINALMOVEMENTSOFLABOUR1-ENGAGEMENTThegreatesttransversediameterBPDpassesthroughthepelvicinletItmayoccurinthelastfewweeksofpregnancyoronlyinlabourespeciallyinmultiparaThefetusentersthepelvisintransverseorobliquediameterLOT40%ROT

20%OP

20%ROP>LOP

ROA/LOA

20%THECARDINALMOVEMENTSOFLABOURAsynclitismThesagittalsuturesoftheheaddeflectsanttowardsthesymphysispubisorposttowardsthesacrum2-DESCENTInnulliparaengagementtakesplacebeforetheonsetoflabour&furtherdescentmaynotoccurtillthe2ndstageInmultiparadescentbeginswithengagementItisgraduallyprogressivetillthefetusisdeliveredItisaffectedbytheuterinecontractions&thinningofthelowersegmentAnteriorasynclitism

Naegele'sobliquityNormalsynclitismPosteriorasynclitism

Litzmann'sobliquityEarpresentation3-FLEXIONThedescendingheadmeetsresistanceofpelvicfloor,Cx&wallsofthepelvisflexionTheshortersuboccipito-begmaticissubstitutedforthelongeroccipito-frontal

Leveractionproducingftexionofthehead;conversionfromoccipitofrontaltosuboccipitobregmaticdiametertypicallyreducestheanteroposteriordiameterfromnearly12-to9.5cm.Ac

Fourdegreesofheadflexion.Indicatedbythesolidlinetheoccipitomentaldiameter;thebrokenlineconnectsthecenteroftheanteriorfontanelwithposteriorfontanel:A.Flexionpoor.B.Flexionmoderate.C.Flexionadvanced.D.Flexioncomplete.Notethatwithflexioncom-pletethechinisonthechest,andthesuboccipitobregmaticdiameter,theshortestanteroposteriordiameterofthefetalhead,ispassingthroughthepelvicinlet.

AcD4-INTERNALROTATIONTurningoftheheadfromtheOTposition

anteriorlytowardsthesymphysispubisie.Occiputmovesfromtransversetoant45oLesscommonlyOTposteriorlytowardsthesacrum135oItisnotaccomplishedtilltheheadhasreachedthespinesThelevator

animusclesformaVshapedslingthattendtorotatethevertexanteriorlyItiscompletedbythetimetheheadreachesthepelvicfloor2/3orshortlyafter?EXTENSIONWhentheflexedheadreachesthevulvaitundergoesextensionthebaseoftheocciputwillbeindirectcontactwiththeinferiormarginofthesymphysispubisCrowningthelargestdiameterofthefetalheadisencircledbythevulvarringTheheadisbornbyfurtherextensionastheocciput,bregma,forehead,nose,mouth&chinpasssuccessivelyovertheperineumEXTERNALROTATION

RESTITUTIONAfterdeliveryoftheheaditreturnstothepositionitoccupiedatengagement,thenaturalpositionrelativetotheshoulders(obliqueposition)RestitutionThenthefetalbodywillrotatetobringoneshoulderanteriorbehindthesymphysispubis(biacromialdiameterintotheAPDofthepelvicoutlet)Restitutionisfollowedbycompleteexternalrotationtotransverseposition(occiputliestonexttoLtmaternalthigh)TheantshoulderslipsunderthepubisBylateralflexionofthefetalbodythepostshoulderwillbedelivered&therestofthebodywillfollow3022.Engagement;descent,flexion6.Restitution(externalrotation)3.Furtherdescent,internalrotation4.Completerotation,beginningextension

Cardinalmovementsinthe