1. Lecture 5 PHASES OF PARTURITION STAGES OF LABOR MECHANISM 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. 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 PHASE 0: UT QUIESCENCE

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. 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 PHASE 1: PREPARATION FOR LABOR

8. 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 PHASE 1: PREPARATION FOR LABOR

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

10. 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 PHASE 1: PREPARATION FOR LABOR

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

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

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

16. 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 1 st STAGE OF LABOR: CLINICAL ONSET OF LABOR

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. Cervical canal obliterated Further effacement of Cx

20. CERVICAL CHANGE INDUCED DURING 1 st STAGE OF LABOR

21. 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 CERVICAL CHANGE INDUCED DURING 1 st STAGE OF LABOR

22. 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 2 nd STAGE OF LABOR: FETAL DESCENT

23. 2 nd 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 2 nd STAGE OF LABOR: FETAL DESCENT

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

26. 4 th 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. 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) LIE, PRESENTATION, ATTITUDE & POSITION

29. 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 LIE, PRESENTATION, ATTITUDE & POSITION

30. 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 LIE, PRESENTATION, ATTITUDE & POSITION

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

32. 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. .'" '.'" ' I !1\!1\ 1 A B i iiFiiF c D Longitudinal 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 (A) vertex (B) sinciput (C) brow (D) face

34. Longitudinal lie. Frank breech presentation. I Longitudinal lie. Complete breech presentation.

35. Longitudinal lie. Incomplete, or footling, breech presentation

36. 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 OP LOTROT LOAROA LOP ROP

37. ~ 'tJ'tJ LONGITUDINAL LIE VERTEX PRESENTATION LOA LOP

38. s A Longitudinal lie. Vertex presentation Right occiput posterior (ROP) Right occiput transverse (ROT)

39. a illa ill (1 bJ 3~(1 bJ 3~ Sf a!Sf a! w Ccw Cc ht p(fit tb feht p(fit tb fe w c al ta tb ojal ta tb oj Right occiput anterior (ROA)

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

41. Longitudinal lie. Face presentation. Left and right anterior and posterior positions. Right mento-posterior Right mento-anterior Left mento-anterior

42. ~ Longitudinal lie. Breech presentation LSP

43. Transverse lie. Right acromio-dorso-posterior position (RADP). The shoulder of the fetus is to the mother's right, and the back is posterior

44. MECHANISM OF LABOUR WITH OCCIPUT PRESENTATIONS THE 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%

45. 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 2 nd 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

46. Anterior asynclitism Naegele's obliquity Normal synclitismPosterior asynclitism Litzmann's obliquity Ear presentation

47. 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

48. Lever action producing flexion of the head; conversion from occipito-frontal to suboccipito-bregmatic diameter typically reduces the anteroposterior diameter from nearly 12 to 9.5 cm

49. A c 4 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 A c D

50. 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

51. EXTENSION When 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 pubis Crowning  the largest diameter of the fetal head is encircled by the vulvar ring The head is born by further extension as the occiput, bregma, forehead, nose, mouth & chin pass successively over the perineum

52. 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) Then 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 left maternal thigh) The anterior shoulder slips under the pubis By lateral flexion of the fetal body the post shoulder will be delivered & the rest of the body will follow

53. 302302 2.Engagement;descent, flexion6. Restitution (external rotation) 3. Further descent, internal rotation 4. Complete rotation, beginning extension Cardinal movements in the mechanism of labor and delivery, left occiput anterior position

54. Mechanism 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) 304304 F tl v bF tl v b a f sa f s

55. OCCIPUT POSTERIOR POSITION Mechanism of labour is identical to OT & anterior varieties The occiput rotate to the symphysis pubis through 135º instead of 90º or 45º If rotation does not occur  direct occiput posterior or partial rotation  transverse arrest

56. Mechanism of labor for right occiput posterior position, anterior rotation,.,.,0,0