The document summarizes the normal physiology of labour and delivery. It describes the three stages of labour as: 1) cervical dilation and effacement, 2) descent and expulsion of the fetus, and 3) delivery of the placenta. Key events in each stage include progressive cervical changes, descent and rotation of the fetus, and uterine contraction and retraction to deliver the placenta. Optimal management focuses on monitoring labour progress, relieving pain, and preventing complications to support the natural birth process.

1. Normal Labour
Dr Tara Manandhar

2. Labour :
• Series of events that place in the genital organ in an effort to expel the
viable products of conception out of the womb through the vagina into
the outer world.
• Term labour
• Preterm labour

3. Delivery:
• Expulsion or extraction of the viable fetus out of the womb
• Normal delivery (vaginal route)
• Delivery via caesarean section

4. Criteria for Normal labour
● 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 mother and
or baby
Abnormal labour

5. Date of Onset of labor
• Naegeles formula ( Expected date of delivery)--?????
• EDD- 4%
• 1 week on either side- 50%
• 2 weeks earlier and 1 week later – 80%
• At 42 weeks - 10%
• At 43 weeks- 4 %

6. Causes of onset of labour:
• Uterine distension: -increases gap junction proteins, receptors for
oxytocin and specific contraction associated proteins (CAPs).
• Fetoplacental contribution: Fetal hypothalamic-pituitary-adrenal
axis

8. Estrogen:

9. Progesterone:
• Increased fetal production of dehydroepiandrosterone sulfate (DHEA-
S) and cortisol
• Inhibits the conversion of fetal pregnenolone to progesterone.
• Progesterone levels therefore fall before labor.

10. • Alteration in the estrogen: progesterone ratio rather than the fall in the
Prostaglandin:
• Initiate and maintain labour.
• Major sites of synthesis of prostaglandins are—
Amnion,
Chorion,
Decidual cells
Myometrium
P

11. Synthesis is triggered by—
• Rise in estrogen level, glucocorticoids, mechanical stretching in late
pregnancy, increase in cytokines (IL–1, 6, TNF), infection, vaginal
examination and separation or rupture of the membranes.
• Prostaglandins enhance gap junction (intramembranous gap between
two cells through which stimulus flows) formation.

12. Biochemical Mechanisms Involved in the Synthesis of Prostaglandins
Phospholipase A2 in the lysosomes of the fetal membranes near term →
esterified arachidonic acid formation of free arachidonic
acid →
synthesis of prostaglandins through
prostaglandin
synthetase.

13. • Prostaglandins (E2 and F2α) diffuse in the myometrium → act directly
at the sarcoplasmic reticulum → inhibit intracellular cAMP generation
→ increase local free calcium ions → uterine contraction

14. Oxytocin and myometrial oxytocin receptors:
(i) Large number of oxytocin receptors are
present in the fundus compared to the
lower segment and the cervix
(ii) Receptor number increases during
pregnancy reaching maximum during
labor.
(iii)Receptor sensitivity increases during labor.

15. Neurological factor
(1) α receptors, which on stimulation, produce a decrease in
cyclic AMP (adenosine monophosphate) and result in contraction
of the uterus
(2) β receptors, which on stimulation,
produce rise in cyclic AMP and result in inhibition of uterine
contraction
release of PGs (E2 and F2α) from amnion and decidua

16. Contractile system of myometrium:
The basic elements involved in the uterine contractile systems are:
(a) Actin
(b) myosin
(c) adenosine triphosphate (ATP)
(d) the enzyme myosin light chain kinase (MLCK) and
(e) Ca++.
• Structural unit of a myometrial cell – myofibril(contains the proteins
—actin and myosin.
• The interaction of myosin and actin is essential for muscle contraction.

17. BraxtonHicks contractions
• Irregular involuntary spasmodic painless uterine contraction with
simultaneous hardening of the uterus.
• Do not increase in frequency or regularity.
• No effect on dilatation of cervix

18. PRELABOR (Premonitory stage):
• In primigravidae - 2–3 weeks before the onset of true labour
• In multiparae -a few days before the onset of true labour
• The features are inconsistent and may consist of the following:
Lightening
Cervical changes

19. Lightening (welcome sign)
• Presenting part sinks into the true pelvis due
to active pulling up of the lower pole of the
uterus around the presenting part.
• Diminishes the fundal height and hence
minimizes the pressure on the diaphragm
• Mother experiences a sense of relief from
the mechanical cardiorespiratory
embarrassment.
• May be frequency of micturition or
constipation due to mechanical factor—
pressure by the engaged presenting part.

21. Cervical changes
A ripe cervix is
(a) soft,
(b) 80% effaced (<1.5 cm in length),
(c) admits one finger easily, and
(d) cervical canal is dilatable.
Appearance of false pain

22. FALSE PAIN (False labor, Spurious labor):
• due to stretching of the cervix and lower uterine segment with
consequent irritation of the neighbouring ganglia .
• Primigravidae > Parous women.
• Usually appears prior to the onset of true labor pain by 1 or 2 weeks in
primigravidae and by a few days in multiparae.

23. Characteristic of False labour pain
(i) Dull in nature
(ii) Confined to lower abdomen and groin
(iii) May be associated with hardening of the uterus
(iv) No other features of true labour pain
(v) Usually relieved by analgesic.

24. Characteristic of True labour pain:
(i) Painful uterine contractions at regular intervals
(ii) Frequency of contractions increase gradually
(iii) Intensity and duration of contractions increase progressively
(iv) Associated with ‘SHOW’’
(v) Progressive effacement and dilatation of the cervix,
(vi) Descent of the presenting part,

25. (vii) Formation of the ‘bag of forewaters’
SHOW:
Expulsion of cervical mucus plug mixed with blood.
Dilatation of internal os:
• cervical canal begins to dilate more in the upper part than in the lower,
• stretching of the lower uterine segment

26. Formation of ‘bag of waters’:
• the membranes are detached easily because of its loose attachment to
the poorly formed decidua.
• With the dilatation of the cervical canal, the lower pole of the fetal
membranes becomes unsupported and tends to bulge into the cervical
canal.
•

27. • As it contains liquor, which has passed below the presenting
part, it is called ‘bag of waters’.
• Formation of bag of membrane with regular contractions and cervical
changes are signs of onset of labour.

28. Physiology of normal labour
• Marked hypertrophy and hyperplasia of the uterine muscle and the
enlargement of the uterus.
• At term, Length of the uterus including cervix - 35 cm (after delivery
20 cm vertically 8 inch and 10 cm anteroposteriorly 4 inch )
• Fundus is wider both transversely and anteroposteriorly than the lower
segment.
• Uterus assumes pyriform or ovoid shape.

29. UTERINE CONTRACTION IN LABOR
• Braxton-Hicks contraction
• Character of the contractions changes with the onset of labor.
• The pacemaker of the uterine contractions is situated in the region
of the tubal ostia from where waves of contractions spread downward.

30. • There is good synchronization of the contraction waves from both
halves of the uterus and also between upper and lower uterine
segments.
• There is fundal dominance of contractions that diminish gradually in
duration and intensity through mid zone down to lower segment.
• It takes about 10–20 seconds.
• The waves of contraction follow a regular pattern.

31. • The upper segment of the uterus contracts more strongly and for a
longer time than the lower part.
• Intra-amniotic pressure rises beyond 20 mm Hg during uterine
contraction.
• Good relaxation occurs in between contractions to bring down the
intra-amniotic pressure to less than 8 mm Hg.
• Contractions of the fundus last longer than that of the mid zone

32. • During contraction, uterus becomes hard and pushed anteriorly to
make the long axis of the uterus in line with that of pelvic axis.
• Simultaneously, the patient experiences pain which is situated more on
the hypogastric region, often radiating to the thighs.
• Pain of uterine contractions - cutaneous nerve distribution of T10 to
L1.
• Pain of cervical dilatation and stretching is referred to the back through
the sacral plexus

33. Probable causes of pain are:
(a) Myometrial hypoxia during contractions (as in angina),
(b) Stretching of the peritoneum over the fundus
(c) Stretching of the cervix during dilatation
(d) Stretching of the ligament surrounding the uterus
(e) Compression of the nerve ganglion

34. Tonus:
• Intrauterine pressure in between contractions and is inversely
proportional to relaxation
During pregnancy- 2–3 mm Hg.
During the first stage of labor - varies from 8 to 10 mm Hg.
The factors which govern the tonus are:
(i) Contractility of uterine muscles,
(ii) intra-abdominal pressure
(iii) over distension of uterus as in twins and hydramnios.

35. Intensity
• Degree of uterine systole.
• The intensity gradually increases with advancement of labor
First stage - raised to 40–50 mm Hg and
Second stage of labor –raised to 100 to 120 mm Hg

36. Duration-
Increases with advancement of labour.
Frequency:
In the early stage of labor- 10 to 15 minutes.
In the second stage- 2 to 3 minutes.

37. Retraction
• Muscle fibers are permanently
shortened once and for all.
Contraction
• Temporary reduction in length of
the fibers, which attain their full
length during relaxation

38. Retraction in normal labor- how does it
help?
● Essential property in the formation of LUS and dilatation and
effacement of the cervix.
● Maintain the descent of the presenting part made by the uterine
contractions and to help in ultimate expulsion of the fetus.
● Reduce the surface area of the uterus favouring separation of placenta.
● Effective haemostasis after the separation of the placenta

39. Stages of labour

40. First stage: (cervical stage of labour)
Onset of true labour pain to full dilatation of the cervix.
Average duration-
Primigravidae- 12 hours
Multiparae- 6 hours

41. Events in the first stage of labour:
• Preparation of the birth canal so as to facilitate expulsion of the fetus
in the second stage.
The main events that occur in the first stage are—
(a) dilatation and effacement of the cervix and
(b) full formation of lower uterine segment.
.

42. Dilatation of cervix
Important structural components of the cervix are—
(a) smooth muscle (5–20%),
(b) collagen and
(c) the ground substance

43. Predisposing factors which favour smooth dilatation:
a. Softening of the cervix.
b. Fibromusculoglandular hypertrophy.
c. Increased vascularity
d. Accumulation of fluid in between collagen fibers
e. Breaking down of collagen fibrils by enzymes collagenase and
elastase

44. f. Change in the various glycosaminoglycans (e.g. increase in
Actual Factors Responsible are:
• Uterine contraction and retraction: ‘polarity of uterus’.
• Fetal axis pressure
• Bag of membrane
• Vis-a-tergo

45. Effacement or Taking up of cervix
• Muscular fibers of the cervix are pulled upward and merges with the
fibers of the lower uterine segment.
• In primigravidae, effacement precedes dilatation of the cervix, whereas
in multiparae, both occur simultaneously.

46. Lower uterine segment
● During labor the demarcation of an active upper segment and a
relatively passive lower segment is more pronounced.
• The wall of the upper segment becomes progressively thickened with
progressive thinning of the lower segment.
• A distinct ridge is produced at the junction of the two, called
physiological retraction ring which should not

47. Anatomical feature of lower uterine segment

48. Clinical significance of lower uterine segment

49. Clinical course of first stage of labour.
● First symptom to appear is intermittent painful uterine contractions
followed by expulsion of blood-stained mucus (show) per vaginam.
● Pain
● Dilatation and effacement of cervix

50. Management of first stage of labour
(1) Non-interference with watchful expectancy.
(2) Monitor the progress of labour, maternal conditions and fetal
behaviour so as to detect any intra-partum complication early.

51. Actual management
A)General—
Antiseptic dressing
Encouragement, emotional support and assurance
Constant supervision is ensured.
• Bowel
• Diet
• Bladder care
• Relief of pain
• Assessment of progress of labour and partograph recording
• Abdominal examination

52. Second stage of labour
• From the full dilatation of the cervix to expulsion of the fetus from the
birth canal.

53. Events in the second stage of labour :
Second stage has two phases:
1. Propulsive—from full dilatation until head touches the
pelvic floor.
2. Expulsive—since the time mother has irresistible desire to ‘bear
down’and push until the baby is delivered.
Average duration:
Primigravidae- 2 hours

54. • Delivery of the fetus is accomplished by the downward thrust offered
by uterine contractions supplemented by voluntary contraction of
abdominal muscles ( bearing down effort) against the resistance
offered by bony and soft tissues of the birth canal.
• Tendency to push the fetus back into the uterine cavity by the elastic
recoil of the tissue of the vagina and the pelvic floor.
• Counterbalanced by the power of retraction.

55. • Thus, with increasing contraction and retraction, the upper segment
becomes more and more thicker with corresponding thinning of lower
segment.
• Endowed with power of retraction, the fetus is gradually expelled
from the uterus against the resistance offered by the pelvic floor.
• After the expulsion of the fetus, the uterine cavity is permanently
reduced in size only to accommodate the afterbirths.

56. Clinical course of second stage of labour
• Pain
• Bearing down effort- Initiated by nerve reflex (Ferguson reflex) due to
stretching of the vagina by the presenting part.
• Membranes may rupture with a gush of liquor per vaginum.
• Descent of the fetus- Abdominal and vaginal examinations.
Abdominal findings are- using fifth formula
Internal examination reveals descent of the head in relation
to ischial spines

57. • Vaginal signs-
• With the descend of presenting part head - distends the perineum, -
scalp hair is visible.
• vulval opening becomes circular (expulsive phase).
• Adjoining anal sphincter is stretched and stool comes out during
contraction.
• The head recedes after the contraction passes off but is held up a little
in advance because of retraction.
• Ultimately, the maximum diameter of the head (biparietal) stretches
the vulval outlet and there is no recession even after the contraction
passes off- ‘crowning’ of the head’.

58. Maternal signs:
• Ëxhaustion
• Immediately following the expulsion of the fetus, the mother heaves a
sigh of relief.
Fetal effects:
Slowing of FHR during contractions is observed, which comes back to
normal before the next contraction

59. Management of second stage of labour
PRINCIPLES:
(1) To assist in the natural expulsion of the fetus
(2) To prevent perineal injuries.

60. General measures-
• The patient should be in bed.
• Constant supervision
• FHR is recorded at every 5 minutes.
• To administer inhalation analgesics
• Vaginal examination –
Confirm its onset but
To detect any accidental cord prolapse.
To find the position and the station of the head
To find the progressive descent of the head.

61. • Preparation for delivery-
Position
Toileting the external genitalia
catheterization the bladder
• Conduction of delivery- divided into three phases :
1. Delivery of the head
2. Delivery of the shoulders
3. Delivery of the trunk

62. • Prevention of perineal laceration: - controlled delivery of the head.
Delivery by early extension is to be avoided.
Spontaneous forcible delivery of the head is to be avoided.
To deliver the head in between contractions.
To perform timely episiotomy

63. • Immediate care of the new born –
Clearing of the air passage and eyes
Clamping and ligaturing of the umbilical cord
APGAR scoring

64. Third stage:
• From expulsion of the fetus to expulsion of the placenta and
membranes (afterbirths).
Average duration –
15 minutes in both primigravidae and multiparae.

65. Events in the third stage of labour :
Mechanism of PLACENTAL SEPARATION:
• A shearing force between the placenta and the placental site.
• The plane of separation runs through deep spongy layer of decidua
basalis.

66. • Two ways of separation of placenta .
(1) Central separation (Schultze):
• Detachment starts at the center resulting in opening up of few uterine
sinuses and accumulation of blood behind the placenta (retroplacental
hematoma).
s

67. (2) Marginal separation (Mathews-Duncan):
• Separation starts at the margin as it is mostly unsupported. With
progressive uterine contraction, more and more areas of the placenta
get separated.
Separation of membrane

68. • Expulsion of placenta- voluntary contraction of abdominal muscles
(bearing down efforts) or by manual procedure
Mechanism of control of bleeding-
• Living ligature.
• Thrombosis
• Myotamponade.

69. Clinical course of third stage of labour
Separation, descent and expulsion of the placenta with its membranes.

70. Before separation of placenta
Per abdomen—
• Uterus becomes discoid in shape, firm in feel and non-ballottable.
• Fundal height reaches slightly below the umbilicus.
Per vaginam-
• Slight trickling of blood.
• Length of the umbilical cord as visible from outside remains static.

71. After separation of placenta
Per abdomen:
Uterus becomes globular, firm, and ballottable.
Fundal height is slightly raised.
Slight bulging in the suprapubic region due to distension of the lower
segment by the separated placenta.
• Per vaginam:
Slight gush of vaginal bleeding.
• Permanent lengthening of the cord is established.

72. • EXPULSION OF PLACENTA AND MEMBRANES:
MATERNAL SIGNS:
• Chills and occasional shivering.
• Slight transient hypotension is not unusual.

73. Management of third stage of labour
Expectant management
Active management of third stage of labour

74. EXPECTANT
MANAGEMENT
• Catheterize the baldder (if
needed)
• Guard the fundus
• Wait for spontaneous separation
of placenta

75. Fourth stage:
• Stage of observation for at least 1 hour after expulsion of the
afterbirths.