Define the terms related to first stage of labour Differentiate the characteristics of true VS false labor. Describe the mechanism in initiation of onset of labor. Describe the physiological and anatomical changes during the 1st stage of labor Explain the 1st stage of labor Explain midwifery roles during first stage of labour

1. COURSE: ADVANCED INTRAPARTUM, POSTPARTUM & NEWBORN CARE (MW603)
MODULE 1: MW:603.1 INTRAPARTUM & POSTPARTUM CARE
TOPIC: PHYSIOLOGICAL AND ANATOMICAL CHANGES DURING 1ST STAGE OF
LABOR
PRESENTER : CESILIA KIMARO HD/MUH/T.431/2022
COODINATOR: DR STELLA EMMANULE (PhD)
FACILITATOR: DR. AGNESS MASSAE (PhD)
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2. At the end of this session each participant should be
able to;
 Define the terms related to first stage of labour
 Differentiate the characteristics of true VS false labor.
 Describe the mechanism in initiation of onset of
labor.
 Describe the physiological and anatomical changes
during the 1st stage of labor
 Explain the 1st stage of labor
 Explain midwifery roles during first stage of labour
2

3.  physiological changes that take place in the first stage
are effacement and dilatation of the cervical os. These
are initiated by the action of various hormones,
prostaglandins, contraction and retraction of the
uterine muscle.
 The length of labour varies widely and is influenced
by parity, birth interval, psychological state,
presentation and position of the fetus.
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4.  Maternal pelvic shape,size and the character
of uterine contractions also affect time scale.
 The greatest part of labour is taken up by the
first stage and it is common to expect the
active phase to be completed within 6–12
hours.(MYLES , 2014).
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5.  Labor: A series of events that take place in the genital organs
in an effort to expel the viable conception out of the womb
through the vagina into outer world (Dutta, 2015).
 Labor is the process of moving the fetus, placenta and
membranes out of the uterus through the birth canal
(Lowdermilk, 2012).
 Normal labor: Is spontaneous expulsion, through the natural
passage (birth canal) of a single, mature (37-42 completed
weeks of pregnancy),live fetus, in vertex, presentation, within
a reasonable time and without fetal or maternal complication
(Dutta, 2015).
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6. First stage of labor begins with the onset of
regular uterine contractions and ends with full
cervical effacement and dilation (Lowdermilk,
2012)
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7.  It starts from the onset of true labor pain and ends
with full dilatation of the cervix.
 It is, in other words, the “cervical stage” of labor. Its
average duration is 12 hours in primigravidae and 6
hours in multiparae. (DUTTA, 2015).
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8. Parameter True labour False labour
Contractions frequency Regular intervals, becoming
close together.
Irregular intervals, not
occurring close together
Contractions intensity Becomes stronger with time. Frequently weak, not getting
strong with time
Contractions location Start in the back and radiates
around toward the front of the
abdomen
Usually felt in the front of the
abdomen
Position changes Contractions continue despite
use of comfort measures
Contractions may stop or slow
down with walking or
changing position
Effect of analgesia Not terminated by sedation or
enema
Frequently abolished by
sedation 1/1/2024 8

9. Parameter True labour False labour
Cervical change Progressive effacement and
dilation and “blood show”
No changes in cervix
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10. Labor initiation is contributed by a multiple
factors that increases uterine contractility.
These include:
Hormonal factors
 Estrogen
 Progesterone
 Prostaglandin
 Oxytocin
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11. Mechanical factors
 Uterine stretching
 Cervical irritation or stretching
 Neurological factors
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12. Fetal Placental hormonal contribution
Activation of fetal hypothalamic-pituitary-
adrenal-axis prior to onset of labor
This process increase CRH → increased
release of ACTH → fetal adrenals → cortisol
→ production of estrogen +prostaglandins
from placenta →Uterine contractions.
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13. Progesterone
 Increase fetal production of dehydroepiandrosterone
Sulphate [DHEA-S] and cortisol which inhibit the
conversion of fetal pregnenolone to progesterone.
 The fall in progesterone prior to labor lead to
imbalance in estrogen-progesterone ratio.
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14. Estrogen
 Increases the release of oxytocin from maternal
pituitary
 Increases excitability of the myometrial cell
membranes.
 Promotes the synthesis of myometrial receptors for
oxytocin (by 100–200 folds), prostaglandins and
increase in gap junctions in myometrial cells.
 Promote the release of prostaglandins from decidua
cells.
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15. Prostaglandin
 Important factors which initiate and maintain labor.
 Synthesized from amnion, chorion decidual cell and
myometrium
 The production triggered by rise in estrogen,
glucocorticoids, mechanical stretching in the late
pregnancy, increase in cytokines (IL–1, 6, TNF),
infection, vaginal examination and separation or
rupture of membranes
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16.  Stretch of the Uterine Musculature
 Stretching smooth muscle organs due to uterine
growing fetus, amniotic fluid volume and fetal
movement increases muscle contractility.
 This increases gap junction proteins receptors for
oxytocin and specific contraction associated proteins
 Stretch or Irritation of the Cervix.
 Stretching or irritation of nerves in the cervix initiates
reflexes to the body of the uterus
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17.  Neurological factors
 Labor can be initiated through nerve pathways.
 Both Alpha (α) and Beta (β) adrenergic receptors in
present in the myometrium.
 Estrogen acts on Alpha receptors and progesterone on
Beta –receptor to function predominantly
 The contractile response is initiated through the
Alpha –receptors of the post ganglionic nerve fiber
around the cervix and the lower part of the uterus.
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18. Labor contractions obey all the principles of
positive feedback:
 The strength of uterine contractions reach
critical value the subsequent contractions
become stronger and stronger until maximum
effect is achieved.
:
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19. Two known types of positive feedback
increase uterine contractions during labor:
 Stretching of the cervix causes the entire body
of the uterus to contract, and this contraction
stretches the cervix even more because of the
downward thrust of the baby's head.
 Cervical stretching also causes the pituitary
gland to secrete oxytocin, which is another
means for increasing uterine contractility
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20. When the labor starts several physiological
and anatomical changes occur in woman body.
The response helps the woman and fetus to
develop mechanisms for adaptation.
These adaptations present objective and
subjective symptoms in woman’s body
systems during labor.
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21. Cardiovascular changes
In each contraction on average 400mls of
blood is emptied from the uterus into the
maternal vascular system.
This increases cardiac output by about 12% to
31% and heart rate slightly increases.
Reduced blood flow due to uterine
contractions increases peripheral vessels
resistance which lead to BP increase.
The increase of 10 mmHg is seen first stage of
labor. 1/1/2024 21

22. Increased physical activity during labor
increases high oxygen consumption and
pronounced by respiration rate increase.
Hyperventilation cause respiratory alkalosis
(an increase in pH), hypoxia, and hypocapnia .
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23.  Decrease of progesterone and increase levels of
estrogen, prostaglandins, and oxytocin triggers
initiation of labor
 Metabolism increases, and blood glucose levels can
decrease with the work of labor.
 Accurate assessment is vital to the mother and fetus
during labor in order to determine deviation from
normal physiological changes
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24.  During labor spontaneous voiding may be
difficult due to:
Tissue edema caused by pressure from the
presenting part.
Discomfort.
Analgesia.
Embarrassment (psychological response)
Proteinuria of +1 is a normal in response to the
breakdown of muscle tissue from the physical
work of labor.
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25.  The downward pressure of the uterus also
compresses the urinary bladder, leading to
frequent urination.
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26. The musculoskeletal system is stressed during
labor.
This results in diaphoresis, fatigue, proteinuria
+1, increased temperature and marked
increased muscle activity.
Backache and joint ache occur as a result of
increased joint laxity at term.
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27. Gastrointestinal motility and absorption of
solid foods are decreased and stomach-
emptying time slowed during labor.
Nausea and vomiting of undigested food eaten
after onset of labor are common.
Nausea and belching due to reflex response to
full cervical dilation.
Woman may report diarrhea accompanied with
onset of labor.
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28. 1.Fundal Dominance
Each uterine contraction starts in the fundus
near one of the cornua and spreads across and
downwards
Contraction lasts longest in the fundus where
its also most intense
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29. Peak is reached simultaneously over the whole
uterus and the contraction fades from all parts
together
This pattern permits the cervix to dilate and
the strongly contracting fundus to expel the
fetus at the end of labour.
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30. 2.Polarity
Is the term used to describe the neuromuscular
harmony that prevails between the two poles
or segments of the uterus throughout labour.
 During each uterine contraction, these two poles act
harmoniously.
 The upper pole contracts strongly and retracts to
expel the fetus.
 The lower pole contracts slightly and dilates to allow
expulsion to take place. If polarity is disorganized
then the progress of labour is inhibited.
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31. 3. Contraction and Retraction
Uterine muscle has a unique property.
During labor the contraction does not pass off
entirely, but muscle fibers retain some of the
shortening of contraction instead of becoming
completely relaxed – RETRACTION
This assists in the progressive expulsion of the
fetus.
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32. 1/1/2024 32

33. 4. Formation of Upper & Lower Uterine Segment
By the end of pregnancy the body of the uterus is
described as having divided into two segments, which
are anatomically distinct
1.Upper segment
The body of the fundus which mainly
concerned with contraction and retraction
Thick and muscular
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34. 2. Lower uterine segment
 Formed from isthmus and cervix
 About 8 – 10 cm long
 Mainly for distension and dilatation
 During pregnancy, the isthmus expands from a length
of 0.5-1 cm to 2.5 cm at term to become the lower
part of the uterine cavity, forming the lower uterine
segment.
 Development of the lower uterine segment begins at
28-30weeks gestation
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35. When labor begins, the retracted longitudinal
fibers in the upper segment pull on the lower
segment causing it to stretch
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36. 1/1/2024 36

37. 5. Retraction Ring/Bandl’s Ring
 A ridge forms between the upper and lower uterine
segments
 The term retraction ring is customary used to describe
the physiological retraction ring
 The bandl’s ring becomes visible above the
symphysis in mechanically obstructed labor where
the lower segment thins abnormally
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38. 1/1/2024 38

39. 1/1/2024 39

40. 6. Cervical effacement
This is the state of thinning and shortening of
the cervix.
The process is believed to take place from
above down.
It leads to widening of the canal at the level of
internal os and the external os remains the
same.
It occurs in late pregnancy (primigravida) or
simultaneously in multi gravida. 1/1/2024 40

41. 1/1/2024 41

42. 7. Cervical dilatation
 The process of enlargement of os uteri from a tightly
closed aperture to an opening large enough to permit
passage of the fetal head.
 Measured in cm ,full dilatation = 10cm.
 This occurs because of uterine action, pressure from
the bag of membrane and the presenting part.
 Pressure applied evenly to the cervix causes the
uterine fundus to respond by contraction
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43. expulsion of mucus plug -pinkish to blood
tinged due to cervical dilatation .
The blood comes from ruptured capillaries in
the parietal decidua where the chorion has
become detached and from dilating cervix.
There should never be frank blood as this is
dangerous.
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44.  At the lower uterine segment, the chorion
becomes detached from it.
The increased intrauterine pressure causes the
loosened part of the sac of fluid to bulge
downwards into the dilating internal os to a
depth of 6-12cm.
A well flexed head fits in the snugly into the
cervix and cuts off fluid in front of the head
from that which surrounds the body.
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45.  This lead to formation of fore and hind waters.
 The effect of separation of waters is to prevent
pressure applied to hind water during contractions
from being applied to the fore water and keeps the
membrane intact at first stage.
 In an intact membrane the pressure from uterine
contraction is exerted on this fluid which is equally
distributed throughout the uterus and over the fetal
body
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46. This occurs at the end of first stage of labor,
when the cervix is fully dilated, high pressure
from uterine contractions and failure to
support the bag of fore water.
But membranes can rupture before beginning
of labor or during first stage of labor.
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47. The first stage of labor is divided into three
phases:
 Latent phase (through 0 to 3 cm of dilation)
 Active phase (4 to 7 cm of dilation)
 Transition phase (8 to 10 cm of dilation).
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48. Latent
Slow, rhythmic contractions radiating from the
lumbar region to the anterior portion of
abdomen.
The contractions last from 30 to 45 seconds
with the intensity gradually increasing.
The frequency of contractions is from 5 to 20
minutes.
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49. There is some cervical effacement.
Dilation is from 0 to 3 cm.
Show is usually present.
The mother is usually able to walk, talk, or
laugh.
Duration of this phase varies, sometimes as
long as 24 hours and is referred to as the
"prolonged latent" phase.
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50. Active
 The contractions become stronger and last longer,
usually 45 to 60 seconds.
 The frequency is from 3 to 5 minutes.
 The cervix dilates from 4 to 7 cm.
 This phase is considered the onset of true labor.
 The mother is admitted to the hospital at this point.
 She is not able to walk, but, desires companionship
and encouragement.
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51. Transient
The contractions are sharp, more intensified,
and last from 60 to 90 seconds.
The frequency is from 2 to 3 minutes.
The cervix dilates from 8 to 10 cm.
Completion of this phase marks the end of the
first stage of labor.
The mother may express feelings of
frustration, loss of control, and irritability.
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52.  To have knowledge of normal physiological and
anatomical changes during labor
 To have clear understanding on assessment of woman
admitted in labor to differentiate normal from
abnormal changes
 To ensure proper management of physiological and
anatomical changes during stages of labor.
 To manage woman and family holistically
 Exercise effective communication through out
management of woman in labor
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53.  The knowledge of normal physiological and
anatomical changes is important in managing woman
during labor.
 The interaction of mechanical and neurological
factors lead to labor start and facilitate its progress.
 Different physiological and anatomical changes
occur during throughout stages of labor for the body
response in adaptation of hormonal and metabolic
adaptations.
 First stage of labor influences the subsequent phases
and need good management for good outome of labor
processes.
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54. DUTTA DC (2015) Textbook Of Obstetrics
including Perinatology and Contraception.
8TH edition.
Franser, D. M., Cooper, M.A., & Nolte A.G.W.
(2014). Myles Text Book for Midwives. 16th
edition, London: Churchill Livingston
Lowdermilk (2012). Maternity & Women’s
Health Care, 10th edition
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