Pathophysiology of Normal Labour by Sunil Kumar Daha

Please find the power point on Management and pathophysiology of Normal Labour . I tried to present it on understandable way and all the contents are reviewed by experts and from very reliable references. Thank you

1. Pathophysiology of labor Sunil Kumar Daha

2. DEFINITION Labor : series of events that take place in genital organs to expel the product of conception (fetus, placenta, membranes) out of womb through the vagina into the external world. Delivery: the expulsion of viable fetus out of the uterus ( vaginal (spontaneous or aided) or abdominal

3. NORMAL LABOR/ EUTOCIA spontaneous in onset and at term with vertex presentation without undue prolongation Natural termination with minimal aids without having any complications affecting the health of the mother and/or the baby

4. ESTROGEN Increases release of oxytocin from maternal pituitary Promotes synthesis of myometrial receptors for oxytocin,PG  increase in gap junctions in myometrial cells Stimulates synthesis of myometrial contraction protein  actinomyosin through cAMP. Increases excitability of myometrial cell

5. PROSTAGLANDIN Initiates and maintain labor Major site of production: Amnion,chorion, decidual cells and myometrium Enhances gap junction formation Triggered by estrogen, glucocorticoids, separation or rupture of membrane

6. OXYTOCIN Peptide hormone Hypothalamus-posterior pituitary Fetal production: Maternal serum increase in second stage of labor Oxytocin receptors: Fundal location, increase during pregnancy Actions Stimulate uterine contractions Stimulate PG production from amnion/decidua

7. TRUE AND FALSE LABOR True labor Painful contractions at regular intervals at term Contraction frequency, intensity, duration increases gradually Associated with Show Progressive effacement and dilatation of cervix Descent of presenting part Formation of “bags of water” Not relieved by enema/ sedatives (analgesics) False labor Dull pain confined to groin and abdomen Pain interval doesn’t shorten Pain intensity remains same No cervical dilatation No hardening of uterus Relieved by enema or sedative

8. DURING PREGNANCY… Marked hypertrophy and hyperplasia of uterine muscles Length of uterus + cervix = 35 cm at term Uterus assumes pyriform/ ovoid shape Cervical canal occluded by thick, tenacious mucus plug

9. UTERINE CONTRACTION IN LABOR Irregular involuntary painless spasmodic uterine contraction (Braxton-Hicks) throughout pregnancy which changes during labor Pacemaker situated in : tubal ostia  contraction waves initiate Pain of contraction distributed along the cutaneous nerve distribution of T10 –L1

10. PATTERN OF CONTRACTION Good synchronization of contraction waves from both halves of the uterus Fundal dominance with gradual diminishing contraction wave through midzone down to lower segment in 10-20 sec Wave of contraction follow regular pattern Upper segment of uterus contracts longer and stronger than lower part Intra-amniotic pressure rises beyond 20mm Hg during uterine contraction Good relaxation occurs in between contraction(intra-amniotic pressure less than 8)

11. RETRACTION Phenomenon of uterus in labor in which muscle fibers are permanently shortened Effects of retraction: Formation of lower uterine segment + dilatation and effacement of cervix Decent of presenting part  expulsion of fetus Reduce surface area  separation of placenta Effective homeostasis after separation of placenta

12. STAGES OF LABOR First phase - latent - Active Second phase Propulsive Expulsive Third phase Fourth phase

13. FIRST STAGE Concerned with formation of birth canal Main events: Dilatation of cervix Effacement of cervix Lower uterine segment formation

14. FACTORS RESPONSIBLE IN DILATATION Uterine contraction and retraction Longitudinal fiber of upper segment attach to circular fiber of lower segment  if uterus contracts canal opens + shortens polarity of uterus Fetal axis pressure longitudinal lie of fetus  circular muscles contraction transmitted from podalic pole to head Not in transverse lie Bag of membrane Vis-a-tergo

15. EFFACEMENT OF CERVIX “ processes by which m uscular fibers of cervix pulled upward and merge with fibers of lower uterine segment” Primigravidae: effacement before dilation of cervix Multiparae : effacement and dilatation occur at same time

16. LOWER UTERINE SEGMENT Formation of active upper segment and relatively passive lower segment forms during labor

17. Friedman’s Curve Friedman's Curve describes progress of two variables over time: dilation of cervix descent of baby Labor is “dysfunctional” when cervix stops dilating or fetal descent stops or both Possible diagnosis of "failure to progress" C-section indicated May be due to CPD (Cephalo Pelvic Disproportion) or epidural anesthesia

18. Friedman’s Curve

19. SECOND STAGE OF LABOR “ Begins when cervical dilatation is complete and ends with fetal delivery.” Median duration 50 minutes in primigravida 20 minutes in multiparous Uterine contractions and accompanying expulsive forces last: 60-90 seconds and recur every 60 seconds

20. Propulsive phase: Period of full dilation until head touches pelvic floor Expulsive phase: Since the time mother has irresistible desire to ‘bear down’ and push until the baby is delivered

21. DURATION OF LABOR Mean length of 1 st and 2 nd stage labor 12 hours in primigravida 6 hours in multipara

22. THIRD STAGE OF LABOR Includes separation, descent and expulsion of placenta with its membrane. Signs of placental separation : Hardening of uterus Sudden gush of blood Rise of Uterus (because the placenta, having separated, passes down in the lower uterine segment and vagina) Lengthening of umbilical cord Signs of placental separation appear within 1-5 minutes within delivery of newborn.

23. FOURTH STAGE OF LABOR The placenta, membranes and umbilical cord should be examined for completeness and for anomalies observation: 1 hour after birth of baby Laceration of birth canal(vagina and perineum): first degree laceration Second degree laceration third degree laceration fourth degree laceration

24. Degree of Lacerations First degree laceration : Involved the perineal skin, vaginal mucus membrane but not underlying fascia and muscle 2 nd degree laceration : Involve in addition, the fascia and muscle of perineal body but not anal sphincter 3 rd degree laceration : Extent further to involve the anal sphincter 4 th degree laceration : Laceration extend through the rectum’s mucosa to exposed its lumen

25. MANAGEMENT OF FIRST STAGE LABOR Monitoring fetal well-being during labor Fetal heart should be monitored every 30 mins in 1 st stage and every 15 mins in 2 nd stage of labor Uterine contractions to evaluate the frequency, duration, and intensity of uterine contractions. Maternal vital signs Maternal temperature, pulse, and blood pressure are evaluated at least every 4 hours with prolonged membrane rupture(>18 hours) antimicrobial administration for prevention of group B streptococcal infections is recommended Subsequent vaginal examinations

26. CONTD.. 5. Oral intake Food should be withheld during active labor and delivery 6. Maternal position position that she finds most comfortable, which will be lateral recumbency most of the time 7. Urinary bladder function Bladder distention-avoided, because it can hinder descent of the fetal presenting parts

27. MANAGEMENT OF SECOND STAGE LABOR 1. Preparation for delivery Put the patient in dorsal lithotomy position or lying flat on bed Clean the vulva, and perineum with antiseptic solution Encourage organized pushing down which she is feeling to do so 2. spontaneous delivery With each contraction, perineum bulges increasing Ritgen maneuver- when head distends the vulva and perineum enough to open the vaginal introitus to 25 cm or more A towel-draped ,gloved hand –used to exert forward pressure on the chin of fetus through the perineum This maneuver allow delivery of head and also favors the neck extension so that head is delivered with small diameter

28. CONT.. Clearing the nasopharynx: Once the thorax –delivered and the newborn can inspire Face quickly wiped and the nares and mouth cleared Nuchal cord : Found in 25% of deliveries and ordinarily no harm If coil of umbilical cord felt-it should be slipped over the head if loose enough If too tight, the loop should be cut between two clamps

29. CONT... Clamping the cord : Umbilical cord is cut between two clamps placed 4 to 5 cm from the foetal abdomen and later an umbilical cord clamp-applied 2 to 3 cm from the fetal abdomen Plastic clamp –safe Timing of cord clamping: If after delivery of the newborn –placed below the level of the vaginal introitus for 3 min and Fetoplacental circulation – not immediately occluded by cord clamping, then approx. 80 ml of blood shift from placenta to neonate  this reduces the frequency of iron deficiency anemia later in infancy

30. MANAGEMENT OF THIRD STAGE LABOR Delivery of the placenta : -Traction on the umbilical cord must not be used to pull the placenta out of uterus. -uterine inversion is one of the complication associated with delivery Manual removal of placenta: - Adequate analgesia is mandatory and aseptic surgical technique should be used -occasionally, placenta will not separate especially common in case of preterm delivery -if there is brisk bleeding and the placenta can not be delivered- indicated

31. CONT... 1.Oxytocin Given before delivery of placenta will decrease blood loss(they may entrap an undiagnosed, undelivered 2 nd twins) The spontaneously labouring uterus is typically sensitive to oxytocin and dosing should be titered to achieved adequate contraction After delivery of the foetus, dosing should be fixed It should be given as a dilute solution by continuous iv. Infusion or im 10 USP unit i.m. (oral not effective) T1/2 3-4 minutes- iv. Infusion (large bolus should not be given)

32. CONT.. CVS effect: IV bolus of 10 unit of oxytocin caused marked fall in BP with an abrupt increase in CO . These hemodynamic changes could be dangerous for women hypovolemic from haemorrhage or those with cardiac disease. Water intoxication: Has antidiuretic action With high dose of oxytocin- produce water intoxication if the oxytocin administered with large volume of electrolyte free aqueous dextrose solution Oxytocin given with NS or ringer solution

33. 2. Ergonovine and methylergonovine : Ergot alkaloids Stimulation of myometrium contraction Given IV (0.1mg),IM or orally(0.25mg) They are dangerous for mother and foetus prior to delivery- tendency of relaxation IV administration sometimes initiation of transient hypotension- severe in gestational hypertension 3. prostaglandins: Analogs not used routinely for management of 3 rd stage labour

34. MANAGEMENT OF FOURTH STAGE LABOR Examine the placenta for their completeness, - anomalies , ( single umbilical artery Multiple births) - length , and - number of vessels in the cord and record the placental weight Suture the episiotomy or any laceration Estimate blood loss, count swabs, and take cord blood for Hb, blood group, Rh, bilirubin, and Coomb’s test for Rh negative mother Check BP, P, T and firmness of the uterus before transferring the patient Allow no food during the first hour, sips of water may be taken

35. DIAMETER OF SKULL AND WAY IT MOVES THROUGH PELVIS

36. FETAL SKULL Made of thin pliable tabular (flat) bones forming the vault Compressible to some extent Areas of skull: Vertex Brow Face

37. Vertex : quadrangular area bounded anteriorly by bregma and coronal sutures Posteriorly by lambda and lambdoid suture Laterally by lines passing through parietal eminences Brow: One side anterior fontanels and coronal sutures Other side root of nose and supra-orbital ridges of either side Face: One side root of nose and supra-orbital ridges On other side junction of floor of mouth with neck

38. SUTURES Frontal : between the two frontal bones Sagittal: between the two parietal bones Two coronal : between the frontal and parietal bones Two lambdoid : between the posterior margins of the parietal bones and upper margin of the occipital bone

39. Diameter Measurement(cm) Attitude of head Presentation Suboccipito-bregmatic (nape of neck to center of bregma) 9.5 cm Complete flexion Vertex Suboccipito-frontal (nape of neck to ant. end of ant. fontanelle ) 10.5 cm Incomplete flexion Vertex Occipito-frontal(occipital eminence to glabella) 11.5 cm Marked deflexion Vertex Mento-verticle (mid point of c hin to highest point on sagittal suture ) 14 cm (13cm in oxford hand book) Partial extension Brow Submento-verticle (junction of floor of mout h and neck to highest point on sagittal suture) 11.5 cm Incomplete extension Face Submento-bregmatic (junction of floor of mouth and neck to center of bregma) 9.5 cm Complete extension Face ANTERO-POSTERIOR DIAMETER OF HEAD THAT MAY ENGAGE

40. Biparietal diameter: 9.5 cm Extends between two parietal eminences Super-subparietal diameter: 8.5 cm Extends from a point placed below one parietal eminence to a point placed above other parietal eminence of opposite side Bitemporal diameter: 8 cm Distance between antero-inferior ends of coronal suture Bimastoid diameter : 7.5 cm Distance between tips of mastoid processes TRANSVERSE DIAMETER CONCERNED IN MECHANISM OF LABOR

41. Attitude of head Plane of engagement Circumference Complete flexion Biparietal-suboccipito-bregmatic Shape - almost round 27.5 cm Deflexed Biparietal-occipito-frontal Shape – oval 34 cm Incomplete extension Biparietal-mento-vertical Shape - bigger oval 37.5 cm Complete extension Biparietal-submento-bregmatic Shape - almost round 27.5 cm CIRCUMFERENCE Circumference of the plane of diameter of engagement differs according to attitude of head Circumference of head in different attitude :

42. MOULDING “ The alteration of the shape of the fore coming head while passing through the resistant birth passage during labor” There is little alteration in size of head as the volume of content inside skull is incompressible An alternation of 4mm in skull diameter commonly occur during normal delivery Disappears within few hours after birth

43. MECHANISM: Compression of engaging diameter of head with corresponding elongation of the diameter at right angle to it GRADING OF MOULDING Grade 1: Bones touching but not overlapping Grade 2: Bones overlapping but easily separated Grade 3: Fixed overlapping of bones

44. IMPORTANCE OF MOULDING Slight moulding is inevitable and beneficial Enables head to pass more easily through the birth canal Extreme moulding may produce  Severe intracranial disturbance in the form of tearing of tentorium cerebelli or subdural haemorrhage Shape of moulding gives information about position of head occupied in pelvis

45. CARDINAL MOVEMENTS OF LABOR

46. the passage of the widest diameter of the presenting part to a level below the plane of the pelvic inlet In the cephalic presentation with a well-flexed head, the largest transverse diameter of the fetal head is the biparietal diameter (9.5 cm) ENGAGEMENT 

47. Engagement can be confirmed clinically by palpation of the presenting part abdominally and/or vaginally The head is assumed to be engaged if the leading edge has reached the ischial spines and there is no significant molding or scalp edema

48. Head in Synclitism : the sagittal suture corresponds to the diameter of engagement with the head enters the brim Anterior asynclitism : Anterior parietal presentation Posterior asynclitism : Posterior parietal presentation Mild degree of asynclitism are common but severe degrees indicate cephalopelvic disproportion PRESENTATION

49. downward passage of the presenting part through the pelvis The greatest rate of descent occurs during the deceleration phase of the first stage and during the second stage of labor Forces involved:- Pressure of amniotic fluid Pressure of fundus upon breech with contraction Maternal abdominal muscles Extension and straightening of fetal body DESCENT

50. Occurs passively as the head descends due to resistance related to the shape of bony pelvis & by the soft tissues of the pelvic floor Although flexion of the fetal head onto the chest is present to some degree in most fetuses antepartum, complete flexion usually only occurs during the course of labor A deflexed head presents a larger diameter, which may be too large to negotiate the pelvic bone FLEXION

51. Rotation of the presenting part from its original position (usually transverse with regard to the birth canal) to the anteroposterior position as it passes through the pelvis As with flexion, internal rotation is a passive movement resulting from the shape of the pelvis and the resistance of the pelvic floor musculature INTERNAL ROTATION

52. Occurs once the fetus has descended to the level of the introitus This descent brings the base of the occiput into contact with the inferior margin of the symphysis pubis At this point, the birth canal curves upwards The fetal head is delivered by extension and rotates around the symphysis pubis EXTENSION

53. After the fetal head deflexes ( extends), it rotates to the correct anatomic position in relation to the fetal torso ; left or right rotation depends on the orientation of the fetus Passive movement resulting from a release of the forces exerted on the fetal head by the maternal bony pelvis and its musculature and mediated by the basal tone of the fetal musculature EXTERNAL ROTATION  

54. Cunningham et.al., Williams OBSTETRICS, 24E, McGraw-Hill Education, 2014, DC Dutta’s textbook of Obstetrics References

55. Thank you