THE PHYSIOLOGY OF NORMAL LABOUR .ppt

Labour is defined as the onset of regular, painful
uterine contractions, more than one every ten
minutes with progressive cervical effacement and
dilatation accompanied by descent of the presenting
Part -obstetrics by Ten Teachers 17th Ed.
Labour or deliveries were probably meant to be
painless during creation but due to the sin of man in
the garden of Eden, God cursed Eve “In pains shalt
thou bring forth children” Abnormal labour simply means a labour that
deviated from normal or poor progress in labour.
The key features of normal labour are:
Spontaneous onset
Single cephalic presentation
37-42 weeks gestation
No artificial interventions
Unassisted spontaneous vaginal delivery
Less than 12hours in Nulliparous women and less than eight hours in multiparous women.
Healthy mother and healthy baby
Retrospective diagnosis

1. PHYSIOLOGY OF NORMAL
LABOUR

2. IntroductionIntroduction
Labour is defined as the onset of regular, painful
uterine contractions, more than one every ten
minutes with progressive cervical effacement and
dilatation accompanied by descent of the presenting
Part -obstetrics by Ten Teachers 17
th
Ed.
Labour or deliveries were probably meant to be
painless during creation but due to the sin of man in
the garden of Eden, God cursed Eve “In pains shalt
thou bring forth children”

3. Abnormal labour simply means a labour that
deviated from normal or poor progress in labour.
The key features of normal labour are:
(1)Spontaneous onset
(2)Single cephalic presentation
(3)37-42 weeks gestation
(4)No artificial interventions
(5)Unassisted spontaneous vaginal delivery
(6)Less than 12hours in Nulliparous women and
less than eight hours in multiparous women.
(7)Healthy mother and healthy baby
(8)Retrospective diagnosis

4. Anatomy of female pelvis Anatomy of female pelvis
and types of pelvesand types of pelves
Symmetrical pelvisSymmetrical pelvis
Gynaecoid pelvis
Android “
Anthropoid “
Platypelloid “
Rachitic “
Generally Contracted Pelvis
Asymmetrical PelvisAsymmetrical Pelvis
Congenital
Acquired

5. Gynaecoid pelvisGynaecoid pelvis
Inlet is oval in shape.
Measurements:
Transverse
diameter
(cm)
Oblique
Diameter
(cm)
A-P
Diameter
(cm)
inlet13.5 12 11
midcavity
12 12 12
Oulet11 12 13.5

6. Fetal Skull MeasurementsFetal Skull Measurements
Suboccipito-bregmatic = 9.5cm
Suboccipito frontal diameter = 10cm
Occipitofrontal diameter = 11cm
Submento–bregmatic diameter = 9.5cm
Occipito-mental = mento – vertical
diameter = 13cm

7. Normal Labor and Birth
•Normal labor and birth are dependent on four
factors - power, passage, passenger and psyche
•All of these factors need to work in synchrony
–Power refers to the expulsive efforts of the
uterus and mother
–Passage refers to the bony and soft tissue of
the pelvis, vagina and perineum
–Passenger refers to the fetus

8. The Power
•The fetus will effect the mechanisms of labor
supported and encouraged by the power of the
uterus and adequacy of the maternal pelvis.
•Failure of the mechanisms of labor to be
effected may be occur because of a decrease in
the power or inadequacy of the passage
•Maternal behavior in labor may not indicate the
power being exerted

9. Aetiology of abnormal Aetiology of abnormal
labourlabour
(1) Powers (Uterine dystocia)
Powers refer to uterine efficiency
(2) The passenger i.e. the fetus with
particular respect to its size, presentation,
position and congenital abnormalities that
may impede progress of labour e.g.
Macrocephaly (megacephaly). Also
placental size and location.
(3) The passage i.e. the uterus, cervix,
vagina and bony pelvis.

10. Inefficient uterine actionInefficient uterine action
This is the most common cause of poor
progress in labour. It is more common in the
following:
•Extremes of reproductive age
•Primigravidae
•Women who are unusually anxious
•uterine overdistension e.g. twins and
polyhydramnious
•Minor degree of CPD or mal-position of the
fetal head.

11. Types of Inefficient Uterine Types of Inefficient Uterine
ActionAction
- Hypotonic
- Hypertonic
- Discoordinated uterine activity
- Lack of voluntary expulsive effort
during the second stage may also
impede the normal course of delivery.

12. Hypotonic InertiaHypotonic Inertia
Implies that contractions are weak and
infrequent and there is normal uterine tone
between contractions.
Hypertonic inertia
Implies that the contractions are irregular and that
there is a high resting basal tone between
contractions. In this circumstance,
the uterine circulation does not return to
normal between contractions, and
consequently fetal distress is more likely.

13. Disco-ordinated Uterine Disco-ordinated Uterine
activityactivity
This may be due to congenital
abnormalities of the uterus:
•Uterine didelphys
•Bicornuate uterus
•Septate and subseptate uterus
•Rudimentary horn etc.

14. PASSENGERSPASSENGERS
A key feature of normal labour is singleton
fetus, longitudinal lie, cephalic
presentation.
Abnormalities of labour due to passengers
include.
- Multiple pregnancy
- Breech presentation

15. - Brow presentation
- Face presentation
-Transverse & oblique lies
-Malpositions e.g. Persistent OP position
and mentoposterior
-Placenta preavia
-Macrosomia
-Macrocephaly (Hydrocephalus)
-Fetal tumours e.g. sacrococcygeal
teratoma

16. PassagePassage
Uterus – aforementioned Congenital
abnormalities may impede progress of labour.
Fibroids, especially those that narrow or block
the birth canal can impede descent of the
presenting part.
Pelvic masses (tumours e.g. ovarian
neoplasm) can also obstruct labour by
compressing the lower segment of the uterus
from outside narrowing the birth canal.

17. Abnormal pelvic typesAbnormal pelvic types
Android pelvis – deep transverse arrest
Platypelloid pelvis – Obstructed labour
Anthoropoid pelvis – Persistent OP
position .
Cervix Cervix
Congenital abnormalities
e.g. diethylstilboestrol - induced.

18. Acquired e.g. conisation of the cervix,
amputation of the cervix (in Manchester
repair) can predispose to cervical stenosis and
cervical dystocia.
Previous cervical lacerations and injuries too.
Tumours of the cervix.
Vagina
Gynae atresia and previous vaginal repairs e.g.
anterior colporrhaphy and posterior
colpoperineorrhaphy either in VVF repair or repair
of prolapse can predispose to dystocia.
Other pelvic floor repairs can predispose to rigidity
& dystocia.

19. Types of Abnormal LabourTypes of Abnormal Labour
These are partogram abnormalities
(1)Prolonged latent phase
(2)Primary dysfunctional labour
(3)Secondary arrest
Prolonged latent phase
This implies a failure of thinning of the lower
segment, effacement and dilatation of the
cervix despite several hours of painful
contractions.

20. Primary dysfunctional labourPrimary dysfunctional labour
This is most common in a first labour, and
implies a slow progress during the active
phase of labour.
It is usually associated with inefficient
uterine contractions.
Secondary arrest
This implies appropriate progress of labour in the initial
phase, but arrest of cervical dilatation typically after
7cm. Commonly associated with mal-position and
CPD.

21. ABNORMAL LABOUR
INTRODUCTION: Please note
•Synonym - Difficult labour - Dystocia
•Labour associated with poor progress either
in 1
st
or 2nd stage of labour evidenced by
either delay or arrest of progress
•By extension, it includes labour associated
with fetal compromise, malpresentation and
induction of labour.
•Labour and delivery - Focus and climax of
the reproductive process.

22. •Involves physical and emotional
challenge to the mother
•Constitutes hazardous journey for the
fetus
•Though brings joy and happiness to the
majority of families, has brought death
and catastrophy to others

23. INCIDENCE OF DISTOCIA
•Varies with different population and different
labour and delivery units
•Far more common in nulliparous women than
multiparous women.
•More common in the 1st stage of labour than
2nd stage
•Occurs in approximately 25% of nulliparous
women ,10-15% of multiparous women.
•Labour abnormalities - common indication for
c/s. Accounts for 7.1% of the 23.6% of overall
c/s rate in USA in 1990 - Norton et al,
1994.

24. ETIOLOGY: Please note
Traditionally causes of slow progress of
labour has been attributed to:
•Powers - Uterine contracting
•Passage - Maternal pelvimetry
•Passenger - Presentation, Position and
size of the fetus
4th factor identified
•Patient - provider relationship.

25. In scientific terms, these represent
•Primary dysfunctional labour
•Fetopelvic/ cephalopelvic disproportion
•Abnormal fetal head position, fetal
abnormalities.
•Epidural analgesia and asynclitism
Note: The term “failure of progress” - Not
a diagnosis but a sign of underlying
problem.

26. DIAGNOSIS OF LABOUR ABNORMALITIES /
PARTOGRAM ABNORMALITIES
•Diagnosis requires close labor monitoring
•Timely diagnosis with prompt medical therapy
improves chances of vaginal delivery.
CLASSIFICATION
1. Arrest disorders
2. Protraction disorders

27. ARREST DISORDERS
1. Prolonged latent phase
• Failure to enter the active phase with
extended period of regular uterine
contraction.
• Not generally classified as arrest disorder:
however normal progress into normal labour
is being arrested.
•In Nulliparous women  No cervical change
with uterine activity for more than 20 hours.
•Multiparous women  No cervical change
for over 14 hours.

28. •Possibly reflects ineffective uterine
contraction without a dominant
myometrial pacemaker.
•Two alternative lines of Mx - Amniotomy
and oxytocin or supportive measures
with hydration and narcotic pain relief.
•Both lines of Mx equally effective.

29. 2) Arrest of cervical dilatation
•No cervical change after 2 hours in active
phase of labour despite uterine activity.
•Most cases due to ineffective uterine
contractions
•Loss of a dominant myometrial pacemaker
with expression of two or multiple
independently firing pacemakers.
•Prompt medical Rx - Oxytocin correction

30. 3) Arrest of Descent
•Occurs when there is failure of descent
in 1 hour of adequate pushing.
•May be due to one or combination of
inadequate uterine contraction, CPD,
abnormal fetal position and asynclitism
•Mx options include oxytocin, operative
vaginal delivery and caesarean delivery
depending on fetal status, station and
maternal status.

31. PROTRACTION DISORDERS
1. Protracted Active Phase
• Slow rate of cervical dilatation with
adequate uterine contraction in active
phase of labour.
• Nulliparous - cervical dilation of <
1.2cm /hr
•Multiparous dilation < 1.5cm / hr
•Most often due to CPD or an
undiagnosed flexion abnormality.
•Oxytocin Rx - often not successful.

32. - May inevitably lead to arrest of dilatation
or descent
- If labor become arrested following
protracted active phase proceed to c/s.

33. 2) Prolonged Deceleration Phase
• Not generally accepted
• Normal progress through labour but
slow progress after 8cm
•Uterine contraction becomes
dysfunctional and not corrected by
oxytocin
•Underlying problems is mostly abnormal
fetal position (e.g OA or OP at high
station) or CPD.
•Rx c/s after adequate trial of oxytocin

34. 3) Proctracted Descent
-Slow rate of descent
Nullipara - less the 1cm / hour
Multipara - less than 2cm/ hour
4) Prolonged 2
nd
stage
• 2
nd
stage > 2hours
•Previously an indication for operative vaginal
delivery or C/s but no more
No need for intervention if FHR tracing is
normal, some gain in station in being made
and mother is comfortable.

35. Abnormal Labour Pattern and diagnostic
Labour Pattern Diagnostic Criteria
Nullipara Multipara
•Prolongation disorders
(Prolonged latent phase) >20hr >14hrs
•Protraction disorders
Protracted Active <1.2cm/hr <1.5cm/hr
phase dilatation
Protracted Descent <1cm/hr <2cm/hr
•Arrest Disorders
Prolonged deceleration phase >3hrs >1hr
Secondary arrest of dilatation >2hrs >2hrs
Arrest of descent >1hr >1hr
Failure of descent - No descent in deceleration phase or
2
nd
stage.
•N.B. The term failure of progress - Not sufficient for
diagnosis.

36. MANAGEMENT OPTIONS OF ABNORMAL MANAGEMENT OPTIONS OF ABNORMAL
LABOURLABOUR
•Once diagnosed, a number of
therapeutic options can lead to vaginal
delivery rather than resort to c/s.
•Oxytocin should be administered 1
st

unless there is a clear contraindication.

37. 1. Mapping the progress of labour
-Use of labour curve
-Partograph with use of alert and action
lines
-Allows timely diagnosis of dysfunctional
labour and prompt application of medical
therapy.

38. 2. Amniotomy
Used for decades in the Mx of slow or
desultory labour.
However its use is controversial
Could speed up normal labour and correct
abnormal ones
Large scale prospective randomized
studies do not support its routine use in
the Mx of dystocia - -
Fraser et al , 1993
- UK Amniotomy
group,1994.

39. Argument against routine Amniotomy
-C/s rate is not lowered
-Modest  intrauterine infection rate if done early (<4cm
dilatation)
-Associated with variable deceleration of FHR due to
umbilical cord constriction.
Argument for
-Excellent method of IOL, if cervix is favourable and fetal
head well applied
-Judicious use after cervical dilation of 5cm  labour
acceleration in multipara . Less so in nullipara.
-Oxytocin works well when membranes are ruptured
-Required for internal monitoring of FHR and uterine
activity.
-May reveal meconium staining of amniotic fluid.

40. 3)Intrauterine Pressure Catheter (IUPC)
-Introduced into the amniotic cavity to help
determine the adequacy of uterine contraction.
-Requires ruptured membranes
-Montevideo units used to quantify uterine
contractility  Average intensity X no of
contraction per 10mins
•Total of 200 MVU - adequate uterine contractility to
effect labour progress.
•No progress with 200MVU  justifies C/S
-However use has not been shown
conclusively to improve labour outcome.
-Best application is to assist nursing personnel
to determine precise timing of uterine
contraction during oxytocin use

41. 4) Epidural Anagelsia
•When used appropriately, can be of great
benefit
•Excessive labour pain greater anxiety 
poor labour progress
•Oxytocin infusion is associated with more
painful uterine contraction.
•Adequate pain relief can aid appropriate
dosing of oxytocin

42. (5) Oxytocin Administration
•Not only result in increase in the frequency of
uterine activity, it also increases total force
generated by & duration of each contraction.
•Best and most appropriate regimen has been
very controversial
•Most important determinant of max. oxytocin
dose & frequency of hyperstimulation  dose
incrementation interval - seitchik and
Castillo, 1982.
•Low dose protocols  lower rate of
hyperstimulation but  rate of c/s - seitchik et
al, 1985.

43. •High dose protocol  greater average dose
of oxytocin,  incidence of hyperstimulation
but lower c/s rates for dystocia, lower
forceps use, lower rates of neonatal sepsis
& shorter admission – delivery interval 
Satin et al, 1994.
•Shorter incremental dosing  associated
with significant lower c/s rate for dystocia
•High dose of oxytocin stimulate higher
proportion of patients earlier  timely
correction of dysfunctional labour and lower
risk of c/s.

44. •Judgment is needed in the use of oxytocin
therapy
–There should be no evidence of feto-
pelvic disproportion (using clinical
pelvimetry & EFW)
–Not used with previous classical c/s
–Used with caution in previous low
transverse c/s
•Used appropriately  very effective.
Inappropriate use  Dangerous for both
mother and fetus.

45. (6)Operative Vaginal Delivery
•The rules for performing successful operative
vaginal delivery hold – full dilatation, engaged fetal
head, known position.
•Primary indication in labour dystocia  arrest of
descent. May be due to insufficient uterine action,
insufficient material pushing effort, abnormal fetal
head position, asynclitism.
•Mother have been pushing for > 2 hours 
exhaustion.
•Appropriate use requires experience of the obgyn in
forceps or vacuum delivery.
•In experienced hands, there is no difference in
neonatal outcome in infants delivery by SVD and
outlet forceps.

46. (7)Caesarean Delivery
•Used when all other measures fail.
•Do not hesitate to operate if successful
vaginal delivery is not possible without
potential serious risk to the fetus and
neonate.

47. Active Management of labour (AMOL)
•Organized package / protocol for
management of nulliparous women in
labour.
•Developed and advocated by obstetric
staff at NMH in Dublin. Initially
developed by Kieran O’ Driscoll.
•Primary goal prevention of prolonged
labour.

48. Basic concepts of AMOL
•Comprehensive prenatal education.
•Admission only after labour is diagnosed.
•Strict criteria for diagnosis of labour.
•Delivery within 12 hours of admission.
•One-on –One nursing care  most
distinguishing feature of AMOL.
 No provision for nursing shift.
•Immediate amniotomy at admission.
•Frequent cervical examinations to ensure
progress in labour  every 1-2 hours.

49. Basic concepts of AMOL(Contd)
• Prompt intervention if labour progress is not
confirmed
•High dose oxytocin protocols
•Epidural analgesia is available
•Mid pelvic and rotational forceps not used
•Continuous internal audit.
•Active involvement of attending obstetrician.
With AMOL - C/s rate for dystocia < 10%
- Oxytocin used in 50-60% of
nulliparas

50. LESSONS FROM AMOL
•Criticized for perceived excessive
intervention.
•However, reduction in c/s rate (25% -
10%) is undeniable.
•Result of studies in AMOL = Conflicting
•Majority of studies  Lower c/s rate and
reduced duration of labour.
 Lopez – Zero et al, 1992 and
Rogers et al, 1997.

51. Meta analysis of studies also confirm similar
result. Glantz, J.C and McNanley T.J
1997.
•Most important component of AMOL in
achieving low C/s rate  one-on-one nursing.
•Most important aspect of this nursing care 
alleviation of maternal anxiety and prompt
diagnosis of dystocia.