Presentation on theme: "MECHANISM OF LABOUR (NORMAL & ABNORMAL)"— Presentation transcript:
1 MECHANISM OF LABOUR (NORMAL & ABNORMAL) Presented ByDr. ZEINAB ABOTALIB MRCOG, DGO,Associate Professor &Consultant Obs/Gyna Infertility & IVF
2 Lie, presentation, attitude, &position FETAL LIEThe relation of the long axis of the fetus to that of the motherLongitudinal lie is found in 99% of labours at termPredisposing factors for transverse lie/oblique lie multiparity, placenta previa, hydramnious, & uterine anomaliesFETAL PRESENTATIONThe presenting part is the portion of the body of the fetus that is foremost in the birth canalThe presenting part can be felt through the Cx on vaginal examinationLongitudinal lie cephalic presentationbreech presentationTransvrse lie shoulder presentation
3 Lie, presentation, attitude, &position CEPHALIC PRESENTATIONHead is flexed sharply vertex / occiput presentationHead is extended sharply face presentationPartially flexed bregma presenting (sinciput presentation)Partially extended brow presentationBREECH PRESENTATIONFrank breechComplete breechFootling breechATTITUDEPosture of the fetus folded on itself to accommodate the shape of the uterusFlexed head, thighs, knees &feetThe arms crossed over the chestFace presentation extended concave contour of the vertebral column
4 (A) vertex (B) sinciput (C) brow (D) face c I D A B .'" 'I! 1\11ABiiFc(A) vertex(B) sinciput(C) browD(D) faceLongitudinal lie. Cephalic presentation. Differences in attitude of fetal body,Note changes in fetal attitude in relation to fetal vertex as the fetal head becomes less flexed.
5 Longitudinal lie. Frank breech presentation. I ILongitudinal lie. Frank breech presentation.Longitudinal lie. Complete breech presentation.
6 Longitudinal lie. Incomplete, or footling, breech presentation.
7 POSITIONThe relation of an arbitrary chosen point of the fetal presenting part to the Rt or Lt side of the maternal birth canalThe chosen pointVertex presentation occiputFace presentation mentumBreech presentation SacrumEach presentation has two positions Rt or LtEach position has 3 varieties : Ant, transverse, postOAROALOAROTLOTROPLOPOP
14 Transverse lie. Right acromiodorsoposterior position (RADP) Transverse lie. Right acromiodorsoposterior position (RADP). The shoulder of the fetus is to the mother's right, and the back is posterior.
15 MECHANISM OF LABOUR WITH OCCIPUT PRESENTATIONS THE CARDINAL MOVEMENTS OF LABOUR 1-ENGAGEMENTThe greatest transverse diameter BPD passes through the pelvic inletIt may occur in the last few weeks of pregnancy or only in labour especially in multiparaThe fetus enters the pelvis in transverse or oblique diameterLOT 40%ROT 20%OP 20% ROP >LOPROA / LOA 20%
16 THE CARDINAL MOVEMENTS OF LABOUR AsynclitismThe sagittal sutures of the head deflects ant towards the symphysis pubis or post towards the sacrum2-DESCENTIn nullipara engagement takes place before the onset of labour & further descent may not occur till the 2nd stageIn multipara descent begins with engagementIt is gradually progressive till the fetus is deliveredIt is affected by the uterine contractions & thinning of the lower segment
18 3-FLEXIONThe descending head meets resistance of pelvic floor, Cx & walls of the pelvis flexionThe shorter suboccipito-begmatic is substituted for the longer occipito-frontal
19 Lever action producing ftexion of the head; conversion from occipitofrontal to suboccipitobregmatic diameter typically reduces the anteroposterior diameter from nearly 12- to 9.5 cm.
20 A. Flexion poor. B. Flexion moderate. C. Flexion advanced. Four degrees of head flexion. Indicated by the solid line the occipitomental diameter; the broken line connects the center of the anterior fontanel with posterior fontanel:A. Flexion poor.B. Flexion moderate.C. Flexion advanced.D. Flexion complete.Note that with flexion complete the chin is on the chest, and the suboccipitobregmatic diameter, the shortest anteroposterior diameter of the fetal head, is passing through the pelvic inlet.AcAcD
21 4-INTERNAL ROTATIONTurning of the head from the OT position anteriorly towards the symphysis pubis ie. Occiput moves from transverse to ant 45ºLess commonly OT posteriorly towards the sacrum 135ºIt is not accomplished till the head has reached the spinesThe levator ani muscles form a V shaped sling that tend to rotate the vertex anteriorlyIt is completed by the time the head reaches the pelvic floor 2/3 or shortly after ¼
22 EXTENSIONWhen the flexed head reaches the vulva it undergoes extension the base of the occiput will be in direct contact with the inferior margin of the symphysis pubisCrowning the largest diameter of the fetal head is encircled by the vulvar ringThe head is born by further extension as the occiput, bregma, forehead, nose, mouth & chin pass successively over the perineum
23 EXTERNAL ROTATION RESTITUTION After delivery of the head it returns to the position it occupied at engagement , the natural position relative to the shoulders (oblique position)RestitutionThen the fetal body will rotate to bring one shoulder anterior behind the symphysis pubis ( biacromial diameter into the APD of the pelvic outlet)Restitution is followed by complete external rotation to transverse position (occiput lies to next to Lt maternal thigh)The ant shoulder slips under the pubisBy lateral flexion of the fetal body the post shoulder will be delivered & the rest of the body will follow
24 2.Engagement;descent, flexion 6. Restitution (external rotation) Cardinal movements in the mechanism of labor and delivery, left occiput anterior position.3022.Engagement;descent, flexion6. Restitution (external rotation)3. Further descent, internal rotation4. Complete rotation, beginning extension
25 304F tl v ba f sMechanism of labor for the left occiput transverse position, lateral view. Posterior asynclitism (A) at the pelvic brim followed by lateral flexion, resulting in anterior asynclitism (B) after engagement, further descent (C), rotation, and extension (D).
26 OCCIPUT POSTERIOR POSITION Mechanism of labour is identical to OT & anterior varietiesThe occiput rotate to the symphysis pubis through 135º instead of 90º or 45ºIf rotation does not occur direct occiput post orPartial rotation transverse arrest
27 ,.,0Mechanism of labor for right occiput posterior position, anterior rotation.