Labour is defined as the process of expelling the products of conception from the uterus through the vagina. Normal labour meets specific criteria including spontaneous onset at term, vertex presentation, natural termination with minimal assistance, and no complications. Abnormal labour deviates from these criteria and risks maternal and fetal health. Labour is initiated by various mechanical, hormonal and neurological factors that trigger uterine contractions and cervical changes over time, eventually resulting in delivery.

2. Labour: Series of events that take place in
the genital organs in an effort to expel the
viable products of conception out of the
womb through the vagina into the outer
world is called labour.

3.  Normal Labour: (EUTOCIA) Labour is called
normal, if it ful fills the following criteria
 Spontaneous in onset & at term.
 With vertex presentation
 Without undue prolongation
 Natural Termination with minimal Aids
 Without having any complication affecting
the health of the mother and/ or baby.
 Abnormal Labour: Any deviation from the
definition of normal labor is called abnormal
labour i.e. the condition that adversely
affecting the maternal and/or fetal prognosis
is called abnormal labour.

4. Causes
Uterine
distension
Feto
placental
contribution
Neurological
factors

5. Can explain the onset of labour at least in twins
or polyhydramnios however,” optimal distension
theory” fails the account for the other wise
causeless preterm labour.
Stretching effect on the myometrium by the
growing fetus and liquor amnii

7. Feto placental contribution
Cascade of events activate feto
hypothalmic pituitary adrenal axis
prior to the onset of labour
Increased CRH
Increased release of ACTH
Fetal adrenals, increased fetal cotisol
secretion
Accelerated production of estrogen
and prostaglandins from the placenta

9. Oestogen – probable causes are
 Increases the release of oxytocin from
maternal pituitary
 Promotes the synthesis of receptors for
oxytocin in the myometrium and decidua
 Accerlates lysosomal disintegration in amnion
cells resulting in increased prostaglandin
synthesis
 Stimulates the synthesis of myometrial
contactile protein –actomycin thro’ camp
 Increases the excitability of the myometrial cell
membranes

10. Progesterone
Increased fetal production of DHEA-S
and cotisol
Inhibits the conversion of feto-
pregnenolene to progesterone
Progesterone levels therefore fall
before labour
Alteration in the
oestrogen:progesterone ratio rather
than the fall in the absolute
concentration of progesterone which
is linked with prostaglandin synthesis

11. Prostaglandins
Prostaglandins are the important factors
which initiate and maintain labour.
The major sites of synthesis of
porstaglandin are- amnion, chorion,
decidual cells and myometrium.
Synthesis is triggered by
Rise in estrogen level, glucocoticoids,
mechanical stretching in late pregnancy,
increase in cytokines, infection, sepration
or rupture of the membranes

12. Oxytocin
There is oxytocin receptors in the
uterus
Oxytocin receptors are increased in
the uterus with the onset of labour
Oxytocin promotes the the release
of prostaglandins from the decidua
Oxytocin synthesis is increased in
the decidua and in the placenta

13.  Although , labour may start in denervated
uterus, labour may also be initated through
nerve pathway. Both alpha & beta adrenergic
receptors are present in the myometrium;
estrogen causing the alpha receptors and
progesterone causing the beta receptors to
function predominantly.

14.  It is found more in primigravida than in parous
women. It is usually appears prior to the onset of
true labour pains, by one or two weeks in
primigravidae and by a few days in multipara.
 Features of false pain:
 Dull in nature and usually confined to the lower
abdomen and groin.
 Continuous and unrelated with hardening of
uterus.
 Without any effect on dilatation of cervix.
 Usually relieved by enema & administration of a
sedation.

15. may begin two to three weeks before the onset of true
labour in primigravida and a few days in multipara the
features are inconsistent and may consist of the following.
 Lightening: 2-3 weeks before the onset of labour the lower
uterine segment expands and allows the fetal head to sink
lower and it may engage in the pelvis, particularly in first
time mothers when this happens the fundus of the uterus
descends and there is more room for lungs, breathing is
easier and the heart and stomach can function more easily .
the woman may experience relief. There may be frequency
of micturition or constipation due to mechanical factor-
pressure by the engaged presenting part. It is a “welcome
sign”.
 Cervical changes: prior to the onset of labour cervix
becomes ripe. A ripe cervix is soft, less than 1.5 cm in
length.
 Appearance of false pain

16.  features are:
 Painful uterine contractions at regular
intervals.
 Contraction with increasing intensity and
duration.
 It occurs as a result of loss of cervical plug
“show” and blood from ruptured capillaries of
parietal decidua. It is blood stained mucoid
discharge.
 Progressive effacement and dilatation of the
cervix.
 Formation of the “bag of waters”

17. During pregnancy there is marked
hypertrophy and hyperplasia of the
uterine muscles and the
enlargement of round ligaments. At
term length of uterus measures
about 35 cm inclunding cervix and
the fundus is much wider.

18.  Throughout pregnancy there is rhythmic
invlountary spasmodic uterine contractions which
are painless and have no effect on dilatation of
cervix, the character of the contractions changes
with the onset of labour. The pace maker of the
uterine contractions is probably situated in the
region of the tubal ostia from where waves of
contraction spread downwards.

20.  There is good synchronization of the contraction
waves of both halves of uterus.
 The waves of contractions follow a regular
pattern
 Intra amniotic pressure rises beyond 20mmhg
with the onset of true labour pains during
contractions.
 Good relaxation occur in between contractions
to bring down the intra amniotic pressure to less
than 8 mmhg.
 During contraction, uterus becomes hard and
some what pushed anteriorly to make the long
axis of the uterus in time with that of pelvic axis
simulataneously patient experiences pain, often
radiating to the thighs.

21.  Myometrial hyoxia during contractions.
 Stretching of the peritoneum over the
fundus.
 Stretching of the cervix during dilatation.
 Compression of the nerve ganglion.

22.  It is the intra uterine pressure in between
the contractions
 During pregnancy, the tonus is of 2-3 mnhg.
 During first stage of labour, it varies from 8-
10mn Hg. It inversely proportional to
relaxation.

23.  The intensity of uterine contraction describes
the degree of uterine systole. The intensity
gradually increases with advancement of labour
while it becomes maximum in second stage
during delivery of baby.
 Intra uterine pressure increases upto 40-50 mnHg
during first stage.
 About 100-120 mnHg in second stage of labour
during contractions.
 Inspite of diminished pain in third stage the intra
uterine pressure is probably the same as that in
second stage.

24.  Duration: In first stage the contractions last
for about 30 secs initially but gradually
increases in duration with the progress of
labour. In second stage contractions last
longer than in first stage.
 Frequency: In the early stage of labour,
contraction comes at interval of10-15 mins.
 In second stage it comes every 2-3 mins.
 It is important to note that all features of
uterine contractions mentioned are very
effective only when they are in combination.

25.  RETRACTION: Retraction is a phenomenon of
the uterus in labour in which muscle fibres
are permanently shortend. Uterine muscles
have this property to become shortened once
and for all. The net effects of retraction in
normal labour are:
 Essential property in the formation of lower
uterine segment and dilatation & effacement
up of the cervix.
 To maintain the advancement of the
presenting part made by uterine contractions
and help in ultimate expulsion of the foetus.