Labour : The process of child birth

STAGES OF LABOUR
EVENTS AND CLINICAL FEATURES
SANTOSH K
RAGIV GANDHI UNIVERSITY OF HEALTH SCIENCES

STAGES OF LABOUR
There are four stages of labour.
 FIRST STAGE(CERVICAL STAGE): It starts from
the onset of true labour pain and ends with full
dilatation of cervix.
Its average duration is 12 hours in primigravidae
and 6 hours in multiparae.

 SECOND STAGE: It starts from the full dilatation of the cervix
and ends with expulsion of fetus from the birth canal.
 Its average duration is 2 hours in primigravidae and 30 min
multiparae.
SECOND STAGE
PROPULSIVE PHASE EXPULSIVE PHASE
Starts from the full Starts with the maternal
dilatation of the cervix bearing down efforts and
up to the descent of the ends with delivery of the
presenting part to the baby.
pelvic floor.

 THIRD STAGE: Begins with the expulsion of the
fetus and ends with expulsion of the placenta and
membranes.
Its average duration is about 15 minutes in both
primigravidae and multiparae.

FOURTH STAGE
 Stage of observation for atleast one hour after
expulsion of the after births.
 Condition of the uterus and general condition of the
patient are carefully monitored.

EVENTS IN THE FIRST STAGE OF
LABOUR
 The first stage is chiefly concerned with the
preparation of the birth canal so as to facilitate
expulsion of the fetus in the second stage. The
main events that occur are:
1) dilatation and effacement of the cervix
2) full formation of the lower uterine segment.

DILATATION OF THE CERVIX
 Prior to the onset of labour, in the pre-labour phase,
there may be certain amount of dilatation of the cervix,
especially in multiparae and in some primigravidae.
 PREDISPOSING FACTORS FAVOURING DILATATION
OF CERVIX :
 Softening of cervix
 Fibromusculoglandular hypertrophy
 Increased vascularity
 Accumulation of fluid in between the collagen fibers
 Breaking down of the collagen fibrils by collagenase and
elastase.
 Increase in the hyaluronic acid and decrease in the
dermatan sulphate levels in the matrix of the cervix.

FACTORS RESPONSIBLE FOR
DILATATION OF THE CERVIX
 UTERINE CONTRACTION AND
RETRACTION:
The longitudinal muscle fibres of the upper
segment are attached to the circular muscle
fibres of the lower segment and the upper part
of the cervix in a bucket holding fashion.
With each contraction the canal is opened from
above down and also becomes shortened and
retracted.

 While the upper segment contracts, retracts and pushes
the fetus, the lower segment and the cervix dilate in
response to the forces of contraction of the upper
segment. This coordination between the fundal
contraction and cervical dilatation is called
― POLARITY OF THE UTERUS‖

BAG OF MEMBRANES
In vertex presentation, the girdle of contact of the
head (that part of the circumference of the head
which first comes in contact with the pelvic brim)
being spherical, may well fit with the wall of the lower
uterine segment.
Thus the amniotic cavity is divided into two
compartments .The part above the girdle of contact
contains the fetus with bulk of the liquor called
hindwaters and the one below it containing small
amount of liquor called forewaters.

 With the onset of labour, the membranes attached
to the lower uterine segment are detached and with
the rise of intrauterine pressure during contractions
there is
herniation of the membranes through
the cervical canal.
 Uterine contractions generate hydrostatic pressure
in the forewaters that in turn
dilate the cervical canal like a wedge.

FETAL AXIS PRESSURE
In labour with longitudinal lie, straightening out of the
fetal vertebral column occurs due to contraction of
circular muscles of the body of uterus.
This allows the fundal contraction to transmit through
the podalic pole into the fetal axis, allowing
mechanical stretching of the lower segment and
opening up of the cervical canal.
With each uterine contraction, there is elongation of
the uterine ovoid and decrease in the transverse
diameter.

VIS-A-TERGO
Final phase of dilatation and retraction of the cervix is
achieved by downward thrust of the presenting part of
the fetus and upward pull of the cervix over the lower
segment.
This phenomenon is lacking in transverse lie where a
thin cervical rim fails to disappear.

EFFACEMENT OR TAKING UP OF
CERVIX
 Effacement is the process by which the muscular
fibres of the cervix are pulled upwards and merges
with the fibres of the lower —uterine segment.
 In primigravidae effacement precedes dilatation of
the cervix, whereas in multiparae, both occurs
simultaneously.

Labour : The process of child birth

LOWER UTERINE SEGMENT
 Before the onset of labour there is no complete
anatomical or functional division of uterus.
 Demarcation becomes pronounced with the
initiation of labour.
 Lower uterine segment develops from the isthmus
of the( non pregnant) uterus – bounded above by
the anatomical os and below by the histological os.
 Formed maximally during labour .peritoneum is
loosely attached anteriorly.
 Measures 7.5-10 cm when fully formed.

CLINICAL COURSE OF FIRST STAGE OF
LABOUR
 The first symptom to appear is intermittent painful
uterine contractions followed by expulsion of blood
stained mucus (show) per vaginam.
 Only few drops of blood mixed with mucus is
expelled and any excess should be considered
abnormal.

 PAIN : The pains are felt more anteriorly with
simultaneous hardening of the uterus.
 Initially, the pains are not strong enough to cause
discomfort and come at varying intervals of 15-30
minutes with duration of about 30 seconds.
 Gradually the interval becomes shortened with
increasing intensity and duration so that in late first
stage the contraction comes at interval of 3-5
minutes and lasts for about 45 seconds.
 Pains are usually felt shortly after the uterine
contractions begin and pass off before complete
relaxation of the uterus.

 Clinically, the pains are said to be good if they
come at intervals of 3-5 minutes and at the height
of contraction the uterine wall cannot be indented
by the fingers.

DILATATION AND EFFACEMENT OF
CERVIX
 Cervical dilatation relates with dilatation of the
external os and effacement is determined by the
length of the cervical canal in the vagina.
 in multiparae, dilatation and taking up occur
simultaneously
 The anterior lip of the cervix is the last to be
effaced. The first stage is said to be completed only
when the cervix is completely - retracted over the
presenting part during contractions.

 Cervical dilatation is expressed either in terms of
fingers— 1, 2, 3 or fully dilated or better in terms of
centimetres (10 cm when fully dilated)
 usually measured with fingers but recorded in
centimetres. One finger equals to 1.6 cm on
average
 effacement of the cervix is expressed in terms of
percentage- 100% (cervix less than 0.25 cm thick)

PARTOGRAPH
 Freidman (1954) first devised it
 composite graphical record of cervical dilatation
and descent of head against duration of labour in
hours
 Cervical dilatation is a sigmoid curve .
 the first stage of labour has got two phases:
 latent phase
 active phase

 The active phase has got three components:
1. Acceleration phase of cervical dilatation of 2.5-4 cm.
2. Phase of maximum slope of 4-9 cm dilatation.
3. phase of deceleration of 9-10 cm dilatation.
In primigravidae, the latent phase is often long ,about 8
hours, during which effacement occurs; the cervical
dilatation averaging only 0.35 cm/hour.
In multiparae, the latent phase is short ,about 4 hours,
and effacement and dilatation occur simultaneously.

Dilatation of the cervix at the rate of 1 cm per hour in
primigravidae and 1.5 cm in multigravidae beyond 3
cm dilatation (active phase of labour), is considered
satisfactory.

STATUS OF THE MEMBRANES
 Membranes usually remain intact until full dilatation
of the cervix or sometimes even beyond, in the
second stage.
 An intact membrane is best felt with fingers during
uterine contraction when it becomes tense and
bulges out through the cervical opening.
 In between contractions, the membranes get
relaxed and lie in contact with the head.
 Variable amounts of liquor escape out through the
vagina after the rupture of the membranes.

MATERNAL SYSTEM
 General condition remains unaffected.
 Feeling of transient fatigue may appear following a
strong contraction.
 Pulse rate is increased by 10-15 beats per minute
during contraction which settles down to its
previous rate in between contractions.
 Systolic blood pressure is raised by about 10 mm
Hg during contraction.
 Temperature remains unchanged.

FETAL EFFECT
 During contractions , slowing of fetal heart rate by
10-20 beats per minute occurs which soon returns
to its normal rate of about 140 per minute as the
intensity of contraction diminishes.

EVENTS IN SECOND STAGE OF
LABOUR
 begins with the complete dilatation of the cervix and
ends with the expulsion of the fetus
 This stage is concerned with the descent and
delivery of the fetus through the birth canal.
 Second stage has two phases :
(A) Propulsive — from full dilatation until head
touches the pelvic floor.
(B) Expulsive — since the time mother has
irresistible desire to ‗bear down and push‘ until the
baby is delivered.

After full dilatation of the cervix, the membranes usually
rupture and there is escape of good amount of liquor amnii.
The volume of the uterine cavity is thereby reduced.
Simultaneously, uterine contraction and retraction become
stronger.
The uterus becomes elongated during contraction, while
the antero-posterior and transverse diameters are reduced.
The elongation is partly due to the contractions of the
circular muscle fibers of the uterus to keep the fetal axis
straight.

 Delivery of the fetus is accomplished by the downward thrust
offered by uterine contractions supplemented by voluntary
contraction of abdominal muscles 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 is
effectively counterbalanced by the power of retraction.
 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 after-
births.

CLINICAL COURSE OF SECOND STAGE OF
LABOUR
 PAIN :
The intensity of the pains increases.
Pain comes at intervals of 2-3 minutes and lasts
for about 1-1 ½ minutes.
It becomes successive with increasing intensity
in the second stage.

BEARING DOWN EFFORTS
 Additional voluntary expulsive efforts that appear
during the second stage of labour (expulsive
phase).
 Initiated by nerve reflex (Ferguson Reflex) set up
due to stretching of the vagina by the presenting
part.
 Sustained pushing beyond the uterine contraction is
discouraged.
 Slowing of FHR may occur during pushing. It
should come back to normal once contractions are
over.

MEMBRANES STATUS:
 Membranes may rupture with a gush of liquor per
vaginam.
 Rupture may occasionally be delayed till the head
bulges out through the introitus.

DESCENT OF THE FETUS
 ABDOMINAL FINDINGS:
 progressive descent of the head, assessed in
relation to the brim.
 Rotation of the anterior shoulder to the midline .
 change in position of the fetal heart rate - shifted
downwards and medially.
o INTERNAL EXAMINATION FINDINGS:
 Descent of the head in relation to ischial spines.
 Gradual rotation of the head evidenced by position
of the sagittal suture and the occiput in relation to
the quadrants of the pelvis.

VAGINAL SIGNS
 As the head descends down, it distends the perineum,
the vulval opening looks like a slit through which the
scalp hairs are visible.
 During each contraction, the perineum is markedly
distended with the overlying skin tense and glistening
and the vulval opening becomes circular.
 adjoining anal sphincter is stretched and stool comes
out during contraction.
 head recedes after the contraction passes off but is held
up a little in advance because of retraction.
 the maximum diameter of the head (biparietal) stretches
the vulval outlet and there is no recession even after the
contraction passes off-CROWNING OF HEAD

 After a little pause, the mother experiences further
pain and bearing down efforts to expel the
shoulders and the trunk.
 Immediately thereafter, a gush of liquor (hind
waters) follows, often tinged with blood.

MATERNAL SIGNS
 features of exhaustion.
 Respiration is slowed
 increased perspiration
 face becomes congested ,neck veins become
prominent during bearing down efforts.
 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.

EVENTS IN THE THIRD STAGE OF
LABOUR
The third stage of labour comprises the stage of
placental separation, its descent into the lower
segment and finally its expulsion with the membranes

PLACENTAL SEPARATION
At the beginning of labour the placental size roughly
corresponds to an area of 20 cm in diameter.
No appreciable diminution of the surface area of the
placental attachment during first stage.
During second stage , slight but progressive
diminution of the surface area following successive
retractions occur, and attains its peak immediately
following the birth of the baby.

MECHANISM OF SEPARATION OF PLACENTA
 Marked retraction reduces the effectively the surface
area of the placental site to its half.
Placenta being inelastic can‘t keep pace with such
an extent of diminution resulting in its debuckling.
A shearing force is instituted between the placenta
and the placental site which brings about the separation
of the placenta from the decidua.
The plane of separation runs through the spongy layer of
decidua basalis . So variable thickness of decidua
covers the maternal surface of the separated placenta.

There are two ways of separation of the placenta:
 CENTRAL SEPARATION (SCHULTZE
METHOD):detachment of the placenta from the uterine
wall attachment starts at the centre resulting in opening
of a few uterine sinuses and accumulation of blood
behind the placenta. With increasing contractions , more
and more detachment occurs facilitated by weight of
placenta and retroplacental blood until the whole of the
placenta gets detached.

 MARGINAL SEPARATION (MATTHEWS- 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 THE MEMBRANES
 The membranes are attached loosely in the active
part. They are thrown into multiple folds.
 Those attached to the lower segment are already
separated during its stretching.
 separation is facilitated partly by uterine contraction
and mostly by weight of the placenta as it descends
down from the active part.
 The membranes so separated carry with them
remnants of decidua vera giving the outer surface
of the chorion its characteristic roughness.

EXPULSION OF THE PLACENTA
 After complete separation of the placenta, it is
forced down into the flabby lower uterine segment
or upper part of the vagina by effective contraction
and retraction of the uterus.
 Thereafter, it is expelled out by either voluntary
contraction of abdominal muscles (bearing down
efforts) or by manual procedure.

MECHANISM OF CONTROL OF
BLEEDING
 After placental separation, innumerable torn sinuses
which have free circulation of blood from uterine and
ovarian vessels have to be obliterated.
 The occlusion is effected by complete retraction where
by the arterioles, as they pass tortuously through the
interlacing intermediate layer of the myometrium, are
literally clamped(LIVING LIGATURE).
 living ligature is the principal mechanism of
haemostasis.
 Thrombosis also occurs which occludes the torn
sinuses. This phenomenon which is facilitated by hyper-
coagulable state of pregnancy.
 Apposition of the walls of the uterus following expulsion
of the placenta (myotamponade) also contributes to
minimise blood loss.

CLINICAL COURSE OF THIRD STAGE
OF LABOUR
PAIN:
 patient experiences no pain for a short time.
 intermittent discomfort in the lower abdomen
reappears, corresponding with the uterine
contractions.

BEFORE SEPARATION OF PLACENTA
ABDOMINAL FINDINGS:
 Uterus becomes discoid in shape
 firm in feel and non-ballottable.
 Fundal height slightly below the umbilicus.
PER VAGINAM:
 slight trickling of blood

AFTER SEPARATION
 PER ABDOMEN :
 Uterus becomes globular, firm and ballottable.
 fundal height is slightly raised as the separated
placenta comes down in the lower segment and the
contracted uterus rests on top of it.
 There may be 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.

EXPULSION OF THE PLACENTA AND
MEMBRANES
 Expulsion is achieved either by voluntary bearing
down efforts or aided by manipulative procedure.
 Followed by slight to moderate bleeding amounting
to 100-250 ml.

MATERNAL SIGNS
 chills and occasional shivering.
 Slight transient hypotension

Labour : The process of child birth

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