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Lecture 5 PHASES OF PARTURITION STAGES OF LABOR MECHANISM OF NORMAL LABOR IN OCCIPUT PRESENTATION

Lecture 5 PHASES OF PARTURITION STAGES OF LABOR MECHANISM OF NORMAL LABOR IN OCCIPUT PRESENTATION. Prof. Vlad TICA, MD, PhD. PHASES OF PARTURITION. Labor : uterine contractions that effect dilatation of cervix and force fetus through birth canal

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Lecture 5 PHASES OF PARTURITION STAGES OF LABOR MECHANISM OF NORMAL LABOR IN OCCIPUT PRESENTATION

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  1. Lecture 5 PHASES OF PARTURITIONSTAGES OF LABORMECHANISM OF NORMAL LABOR IN OCCIPUT PRESENTATION Prof. Vlad TICA, MD, PhD

  2. PHASES OF PARTURITION • Labor : uterine contractions that effect dilatation of cervix and force fetus through birth canal • Parturition: bringing forth of young, encompass all physiological processes involved in birthing • Phase 0: Prelude to Parturition • Phase 1: Preparation for Labor • Phase 2: Process of Labor • Phase 3: Parturition Recovery

  3. PHASES OF PARTURITION & ONSET OF LABOR • Divide 4 uterine phases: correspond to major physiological transient of myometrium and cervix during pregnancy

  4. PHASE 0: UT QUIESCENCE • Uterine smooth m tranquility with maintenance of cervical structural integrity • Unresponsive to natural stimuli, contractile paralysis • Myometrium : quiescent state • Cervix : firm unyielding • Successful anatomical structural integrity :essential for successful parturition • Some myometrial contraction occur not cause cervix dilation  Braxton-Hicks contraction / false labor

  5. PHASE 0: UT QUIESCENCE • Braxton – Hicks contraction or false labor • myometrial contractions that do not cause cervical dilatation • unpredictability in occurrence • lack of intensity • brevity of duration • discomfort – confined to low abdomen & groin

  6. PHASE 1: PREPARATION FOR LABOR • Uterine awakening or activation • Progression of change in uterus during last 6-8 weeks of pregnancy • Cervical change • Myometrial change

  7. PHASE 1: PREPARATION FOR LABOR CERVICAL CHANGE • Initiation of parturition: Cx soften, yield, more readily dilatable • Fundus transformed to produce effective contraction that drive fetus through Cx & birth canal • Failure of coordinated interaction  unfavorable preg outcome

  8. PHASE 1: PREPARATION FOR LABOR CERVICAL CHANGE • Change of state of bundles of collagen fiber • Collagen breakdown & rearrangement of collagen fiber bundles (number & size) • Chages in relative amount of glycosaminoglycans (hyaluronic acid, capacity of Cx to retain water) • Dermatan sulfate (need for collagen fiber cross linking) • Production of cytokine  degrade collgen • Cx thinning, softening relaxation Cx initiate diatation

  9. PHASE 1: PREPARATION FOR LABOR CERVICAL CHANGE • PG E2 & F2a : modification of collagen & alteration in relative amount of glycosaminoglycans  Cx softening or ripenning to facilitate induction of labor

  10. PHASE 1: PREPARATION FOR LABOR MYOMETRIAL CHANGE • Increase Ut irritability & responsiveness to uterotonins • Alterations in expression of key enzyme CAP (contraction-associated proteins) - control myometrium contractility • Myometrial oxytocin R • Myometrial cell gap junction protein (ex connexin -43) • Formation lower Ut segment

  11. PHASE 2 : PROCESS OF LABOR • Active labor : Ut contrations bring about progressive cervical dilatation & delivery • 3 stage of labor

  12. PHASE 2: PROCESS OF LABOR 1st STAGE OF LABOR • begins when uterine contraction of sufficient frequency, intensity & duration • ends when Cx is fully dilatated (10cm) • stage of cervical effacement & dilatation 2nd STAGE OF LABOR • begins when complete dilatation of Cx • ends with delivery of fetus • stage of expulsion of fetus

  13. PHASE 2: PROCESS OF LABOR 3rd STAGE OF LABOR • begins after delivery of fetus • ends with delivery of placenta and fetal membranes • stage of separation & expulsion of placenta 4th STAGE OF LABOR • begins after placenta and fetal membranes • ends after 2 hours • stage of immediate puerperium

  14. PHASE 2: PROCESS OF LABOR

  15. PHASE 2: PROCESS OF LABOR

  16. 1st STAGE OF LABOR: CLINICAL ONSET OF LABOR • Formation of distinct lower & upper Ut segment: • 2 distinct parts (anatomically & physiologically) • 1. UPPER SEGMENT • actively contracting • becomes thicker as labor advances • quite firm or hard • 2. LOWER SEGMENT • relatively passive • develops into a much thinly walled passage for the fetus • much less firm

  17. SEQUENCE OF DEVELOPMENT OF SEGMENT & RING IN UTERUS IN PREGNANT WOMEN AT TERM & IN LABOR

  18. Cx near end of pregnacy before labor Beginning effacement of Cx

  19. Further effacement of Cx Cervical canal obliterated

  20. CERVICAL CHANGE INDUCED DURING 1st STAGE OF LABOR

  21. CERVICAL CHANGE INDUCED DURING 1st STAGE OF LABOR • 2 phases of cervical dilatation: • 1. LATENT PHASE • more variable • subject to sensitive changes by extraneous factors & • by sedation (prolongation) & myometrial stimulation • (shortening) • 2. ACTIVE PHASE • acceleration phase - usually predictive of outcome • phase of maximum slope • deceleration phase

  22. 2nd STAGE OF LABOR: FETAL DESCENT • In many nulliparas • engagement accomplished before labor begins • further descent not occur until late in labor • increased rates of descent are ordinarily observed • during the phase of maximum slope

  23. 2nd STAGE OF LABOR: FETAL DESCENT

  24. Labor course divided fuctionally on basis of expected evolution of dilatation & descent curves into 3 divisions: PREPARATORY DIVISION - latent & acceleration phases DILATATIONAL DIVISION - phase of maximum slope of cervical dilatation - most rapid rate of dilatation occur PELVIC DIVISION - deceleration phase & second stage while concurrent with phase of maximum slope of fetal descent 2nd STAGE OF LABOR: FETAL DESCENT

  25. 3rd STAGE OF LABOR: DELIVERY OF PLACENTA & MEMBRANES

  26. 4th STAGE OF LABOR: IMMEDIATE PUERPERIUM

  27. PHASE 3 OF PARTURITION: PROCESS OF LABOR • Immediately after delivery & for 2 hours or so thereafter, myometrium in state of rigid & persistent contraction & retraction  effect compression of large Ut vessels  Severe PPH prevented • Involution of Ut & reinstitution of ovulation • Complete Ut involution : 4~6 wks • Infertility persist as long as breast feeding is continued ( lactation  anovulation & amenorrhea)

  28. LIE, PRESENTATION, ATTITUDE & POSITION FETAL LIE • The relation of the long axis of the fetus to that of the mother • Longitudinal lie - found in 99% of labours at term • Transverse lie - multiparity, placenta praevia, hydramnios, uterine anomalies • Oblique lie: unstable (become logitudinal or transversal) • By abdominal palpation, vaginal examination, and auscultation, or by technical means (USG, X-ray)

  29. LIE, PRESENTATION, ATTITUDE & POSITION FETAL PRESENTATION • The presenting part is the portion of the body of the fetus that is foremost in the birth canal • The presenting part can be felt through the cervix on vaginal examination • Longitudinal lie  cephalic presentation  breech presentation • Transverse lie  shoulder presentation

  30. LIE, PRESENTATION, ATTITUDE & POSITION CEPHALIC PRESENTATION • Head is flexed sharply  vertex / occiput presentation • Head is extended sharply  face presentation • Partially flexed  bregma presenting (sinciput presentation) • Partially extended  brow presentation

  31. LIE, PRESENTATION, ATTITUDE & POSITION BREECH PRESENTATION • Frank breech • Complete breech • Footling breech

  32. LIE, PRESENTATION, ATTITUDE & POSITION ATTITUDE • Posture of the fetus  folded on itself to accommodate the shape of the uterus • Flexed head, thighs, knees &feet • The arms crossed over the chest • Face presentation  extended concave contour of the vertebral column

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

  34. POSITION The relation of an arbitrary chosen point of the fetal presenting part to the Rt or Lt side of the maternal birth canal The chosen point: • Vertex presentation  occiput • Face presentation  mentum • Breech presentation  sacrum Each presentation has 2 positions: Rt or Lt Each position has 3 varieties : anterior, transverse, posterior OA ROA LOA ROT LOT LOP ROP OP

  35. LONGITUDINAL LIE VERTEX PRESENTATION LOA LOP

  36. Right occiput posterior (ROP) Right occiput transverse (ROT)

  37. FREQUENCY OF VARIOUS PRESENTATIONS & POSITIONS AT TERM • Vertex  96% 2/3 Lt 1/3 Rt • Breech  3.5% • Face 0.3% • Shoulder0.4%

  38. Right mento-anterior Right mento-posterior Left mento-anterior

  39. Longitudinal lie. Breech presentation LSP

  40. MECHANISM OF LABOUR WITH OCCIPUT PRESENTATIONSTHE CARDINAL MOVEMENTS OF LABOUR 1 - ENGAGEMENT The greatest transverse diameter BPD passes through the pelvic inlet It may occur in the last few weeks of pregnancy or only in labour especially in multipara The fetus enters the pelvis in transverse or oblique diameter • LOT  40% • ROT  20% • OP  20% ROP > LOP • ROA / LOA 20%

  41. THE CARDINAL MOVEMENTS OF LABOUR • Asynclitism The sagittal sutures of the head deflects ant towards the symphysis pubis or post towards the sacrum 2 - DESCENT • In nullipara engagement takes place before the onset of labour & further descent may not occur till the 2nd stage • In multipara descent begins with engagement • It is gradually progressive till the fetus is delivered • It is affected by the uterine contractions & thinning of the lower segment

  42. 3-FLEXION • The descending head meets resistance of pelvic floor, Cx & walls of the pelvis  flexion • The shorter suboccipito-begmatic is substituted for the longer occipito-frontal

  43. 4-INTERNAL ROTATION • Turning of the head from the OT position  anteriorly towards the symphysis pubis ie. Occiput moves from transverse to anterior 45º • Less commonly OT  posteriorly towards the sacrum 135º • It is not accomplished till the head has reached the spines The levator ani muscles form a V shaped sling that tend to rotate the vertex anteriorly • It is completed by the time the head reaches the pelvic floor 2/3 or shortly after ¼

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