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ANKITA PPT FINAL.pptx....................
1. STAGES OF LABOUR AND
MECHANISM OF LABOUR
PRESENTED BY-DR.ANKITA CHOURASIA (JR1)
GUIDED BY- DR.DIVYA KHARE(ASSOCIATE PROFESSOR)
DEPARTMENT OF OBSTETRICS AND GYANECOLOGY
2. LABOUR
• Series of events that take place in the genital organs in an effort to expel the viable
products of conception (fetus, placenta and the membranes) out of the womb
through the vagina into the outer world is called Labor.
• NORMAL LABOR (EUTOCIA)
• Labor is called normal if it fulfills the following criteria.
• (1) Spontaneous in onset and at term.
• (2) With vertex presentation.
• (3) Without undue prolongation.
• (4) Natural termination with minimal aids.
• (5) Without having any complications affecting the healthof the mother
and/or the baby.
4. Stages of True Labour
• 1.First Stage of Labor -Begins with the onset of true labor pains
and ends with full cervical dilatation (10 cm)
• Duration: Primigravida (first-time mother): approximately 12 Hr
Multipara (previous deliveries): approximately 6 hours
• 2.Second Stage of Labor -Extends from full cervical dilatation to
complete expulsion of the fetus.
• Duration: Primigravida: 0 minutes to 2 hours
Multipara: up to 30 minutes
5. • 3.Third Stage of Labour- Begins after the delivery of the
fetus and ends with the expulsion of the placenta and
membranes .
•Duration: Average 15 minutes in both primigravida and
multipara can be reduced to 5 minutes with Active
Management of Third Stage of Labor (AMTSL)
•4.Fourth Stage of Labour -The first hour following the
delivery of the placenta, also considered a period of
observation.
6. Actual Factors Responsible are:
• Uterine contraction and retraction—The longitudinal muscle fibers
of the upper segment are attached with circular muscle fibers of
the lower segment and upper part of the cervix in a bucket-holding
fashion Thus, with each uterine contraction, not only the canal is
opened up from above down but also it becomes shortened and
retracted. There is some co-ordination between fundal contraction
and cervical dilatation called “polarity of uterus”.
• 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 upper segment.
7. Fetal axis pressure:
• In labor with longitudinal lie and with well-fitted (flexed) fetal head on the
cervix, fetal vertebral column is straightened by the contractions of the circular
muscle fibers of the body of the uterus.
• This allows the fundal strong contraction force to be transmitted through the
fetal podalic pole and vertebral column to the well-fitted fetal head.
• This causes mechanical stretching of the lower segment and opening up
(dilatation) of the cervical canal.
• With each uterine contraction, there is elongation of the uterine ovoid and
decrease in the transverse diameter. In transverse lie fetal axis pressure is absent.
• With progressive contraction and retraction, the upper segment becomes shorter
and thicker while the lower segment becomes thinner and wider. The cervical
canal starts dilating.
8. Bag of membranes:
• The membranes (amnion and chorion) are attached loosely to the
decidua lining the uterine cavity except over the internal os.
• 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.
.The amniotic fluid is divided into two compartments.
10. • 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 labor, 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.
• There is ball-valve like action by the well-flexed head. Uterine
contractions generate hydrostatic pressure in the forewaters that in
turn dilate the cervical canal like a wedge.
• When the bag of forewaters is absent (PROM) the pressure of the
presenting part pushes the cervix centrifugally.
11. EFFACEMENT OR TAKING UP OF CERVIX:
• Effacement is the process by which the muscular fibers of the cervix
are pulled upward and merges with the fibers of the lower uterine
segment.
• The cervix becomes thin during first stage of labor or even before that
in primigravidae.
• In primigravidae, effacement precedes dilatation of the cervix,
whereas in multiparae, both occur simultaneously (Fig. 13.6).
Expulsion of mucus plug is caused by effacement.
13. Uterine Contractions in Pregnancy and Labour
• Throughout pregnancy and labor, uterine contractions undergo significant
changes in pattern, intensity, and clinical relevance.
During pregnancy: Braxton Hicks contractions are painless, irregular, and non-
progressive.
During labor: Contractions become painful and cause cervical dilatation.
Pacemaker of uterine contractions is located at the uterine cornu (right side
predominates).
Contractions spread at 2 cm/sec and depolarize the entire uterus within 15 seconds.
Contractions are strongest in the fundal region.
Adequate uterine contractions: 3 contractions in 10 minutes, each lasting 45 seconds.
14. Tachysystole: >5 contractions in 10
minutes (averaged over 30 mins);
applies to spontaneous or induced
labor.
≥6 contractions in 10 minutes may
cause fetal distress.
Hypotonic contractions: Intensity
<25 mmHg or frequency <2 in 10
minutes.
15. First Stage of Labor: Cervical Effacement and Dilatation
It is divided into two distinct phases: the Latent Phase and the Active Phase.
Feature Latent Phase Active Phase
Definition Begins with true labor
pains, ends at 3–5 cm
cervical dilation
Begins at 3–5 cm dilation
with regular uterine
contractions
Main Event Primarily cervical
effacement
Primarily cervical dilatation
Duration (Nulliparous) Average: 8.6 hrs
Max: 12 hrs
Progress rate: ≥ 1.2 cm/hr
Duration (Multiparous) Average: 5.6 hrs
Max: 8 hrs
Progress rate: ≥ 1.5 cm/hr
Minimum Progress Rate — At least 1 cm/hr
16. Abnormalities of Latent Phase
Prolonged Latent Phase:
• >20 hours in nulliparous women
• >14 hours in multiparous women
🔹 Common Causes:
• Excessive sedation or epidural analgesia
• Poor cervical conditions (e.g., thick, uneffaced, undilated cervix)
• False labor (most common in multipara.
17. Abnormalities of Active Phase
Minimum cervical dilatation rate:
• Nulliparous: 1.2 cm/hr
• Multiparous: 1.5 cm/hr
📉 Protracted Active Phase:
Cervical Dilatation:
• Nulliparous <1.2 cm/hr
• Multiparous <1.5 cm/hr
Descent of Head:
• Nulliparous <1 cm/hr
• Multiparous <2 cm/hr
•
✅ Management: Expectant and support. If CPD present → Cesarean section.
18. ⛔ Arrest :
Arrest of dilatation: No progress for ≥2 hrs
Arrest of descent: No progress for ≥1 hr
ACOG Criteria for First Stage Arrest Diagnosis:
1. 1. Latent phase is complete (≥4 cm dilated)
2. 2. Adequate uterine contractions: ≥200 MV units in 10 min over 2 hours without cervical
change
📌 Note: Williams suggests observing for ≥4 hours before diagnosing arrest
Factors contributing to arrest: Excessive sedation, epidural, malposition, CPD
•Therapy: Expectant for protracted labor; oxytocin if no CPD
19. Second Stage of Labour
Begins with full cervical dilatation and ends with delivery of the fetus.
Expulsive maternal efforts are more important than uterine
contractions.
⏱ Normal Duration:
• Nulliparous: 1 hour
• Multiparous: 30 minutes
20. ⏱ Prolonged Second Stage:
⏱ • Without epidural:
- Nulliparous: >2 hrs (+1 hr for arrest)
- Multiparous: >1 hr (+1 hr for arrest)
With epidural:
- Nulliparous: >3 hrs (+1 hr for arrest)
- Multiparous: >2 hrs (+1 hr for arrest)
•
🚫 Second Stage Arrest: No descent for ≥1 hr beyond prolonged
duration.
21. Third Stage of Labour
• The third stage of labor begins with the birth of the baby and ends with the expulsion of the placenta
and membranes along with uterine contraction and retraction.
Feature Expectant Management Active Management
Placenta
Separation
Occurs naturally without
intervention
Actively facilitated with
medical assistance
Uterine
Contraction
Depends on physiological
response
Stimulated with uterotonic
agents
Duration Up to 15 minutes ~5 minutes
Blood Loss
Risk
Higher blood loss Minimal blood loss
PPH Risk Increased chance of
Postpartum Hemorrhage
(PPH)
Significantly reduced
Maternal
Mortality
Higher risk Lower risk
🩺 Management Approaches
22. Components of Active Management of Third Stage
of Labour (AMTSL)
Administration of a uterotonic drug → e.g., Oxytocin 10 IU IM
immediately after baby’s birth
Delayed cord clamping → Clamping the cord after 1–3 minutes
Controlled cord traction (CCT) → Gentle traction on the cord with
counter-pressure on the uterus
Uterine massage → Performed after placenta delivery to enhance
uterine contraction
23. FOURTH STAGE OF LABOUR
• Pulse, blood pressure, tone of the uterus (well retracted) and any
abnormal vaginal bleeding are to be watched at least for 1 hour after
delivery.
• When fully satisfied that the general condition is good, pulse and
blood pressure are steady, the uterus is well retracted and there is no
abnormal vaginal bleeding, the patient is sent to the ward.
24. Indications of Early Cord Clamping
Preterm or growth-restricted fetus – due to risk of hypervolemia; even
an extra 40–50 mL of blood can cause congestive heart failure (CHF) in
premature infants, so the cord is clamped immediately
Birth asphyxia – immediate resuscitation takes priority over delayed
cord clamping
Rh isoimmunization
HIV-positive mother
Maternal diabetes
25. Signs of Placental Separation
Per Abdomen:
Uterus becomes globular, firm and ballottable (earliest sign to appear)
Fundal height is slightly raised as the separated placenta comes down
in the lower segment and uterus rests over it (Schroeder's sign)
Slight suprapubic bulging may be seen due to separated placenta
distending the lower segment
On pushing the uterus cephalad with a hand on the abdomen, the cord
no longer recedes (Kustner's sign)
26. MECHANISM OF NORMAL LABOUR
• The series of movements that occur in the fetal head during its passage
through the birth canal is called the mechanism of labor.
• Mechanism -The head usually enters the pelvic brim through the transverse
diameter (~70% cases).
• Less commonly, it enters through one of the oblique diameters. Common
positions at engagement:
• Left occipitoanterior (LOA) is slightly more common than right occipitoanterior
(ROA).
• The engaging anteroposterior diameter of the head
:Suboccipitobregmatic – 9.5 cm (3¾") – in well-flexed head.Suboccipitofrontal –
10 cm (4") – in slight deflexion.
27. Descent
• Descent is the downward movement of the fetal head through the birth canal.
• It is a continuous process throughout labor.
• Slow or minimal during the first stage of labor.
• Becomes more noticeable and rapid in the second stage.
• Completed with the delivery of the baby.
• In primigravidae (first-time mothers),descent usually begins after full cervical
dilatation.
• In multiparae (women who have delivered before), descent may start earlier
with engagement.
• By full dilatation,the head is expected to reach the pelvic floor.
• Factors helping descent:Uterine contractions and retraction Bearing down efforts
(mother's pushing)
28. Engagement and Asynclitism
• Before engagement, imaging shows the fetal head is often tilted sideways.This
causes the sagittal suture to shift from the center,it may tilt forward toward the
pubis or backward toward the sacrum.
• This tilt is called asynclitism.If the suture shifts forward (toward the pubis), the
posterior parietal bone leads. This is called posterior asynclitism, and it's more
common in primigravida (first-time mothers).
29. Flexion
• As soon as descending head meets resistance from the cervix
,pelvic wall or pelvic floor during descent ,full flexion is achieved.
The chin is brought into contact with fetal thorax &the presenting
Engaging diameter of fetal head changes from occipito frontal (11.0cm )
to suboccipito-bregmatic (9.5cm) for optimal passage of fetal head
through the pelvic.
30. Internal rotation
• Internal rotation is a key movement that allows further descent of the fetal
head during labor.
• Without internal rotation, labor cannot progress normally.The mechanism is
complex and depends on the fetal position
• In occipitolateral position, the occiput rotates forward by 2/8th of a circle.In
oblique anterior position, it rotates 1/8th of a circle forward, placing the
occiput behind the symphysis pubis.
• Descent and internal rotation occur together.
Factors for successful anterior internal rotation:Well-flexed fetal head,Strong
and coordinated uterine contractions, Favorable midpelvic shape,Good tone of
levator ani muscles
31. Torsion of the neck
• Torsion of the neck occurs during internal rotation of the fetal head.
• It is an inevitable and natural phenomenon in the mechanism of labor.
• If the shoulders remain in the anteroposterior (AP) diameter, the neck
must twist (torsion) by 2/8th of a circle to allow head rotation.
• The neck cannot tolerate such a large degree of torsion.To reduce the
stress on the neck, the shoulders also rotate slightly in the same direction.
• This partial shoulder rotation (by one-eighth of a circle) shifts them into
the oblique diameter.
• Therefore, only one-eighth of torsion remains in the neck after this
adjustment.
32. Crowning
• Crowning:Occurs after internal rotation of the head.
• Further descent continues until the subocciput lies beneath the pubic
arch.
• The biparietal diameter (largest transverse diameter of the head)
stretches the vulval outlet.
• No recession of the head occurs after the contraction ends.This stage
is called “crowning of the head.”
33. Extension
• Extension of the head occurs due to the "couple of force“
• mechanism.There are two opposing forces:
• Driving force: pushes the head downward.Pelvic floor resistance:
pushes the head upward and forward.
• These two forces neutralize each other in vertical direction.
• The remaining forward thrust causes the head to extend.
• The fetal head emerges in this order:Vertex (top of the head),Brow
(forehead),Face.
34. Restitution
• Restitution is a passive movement of the fetal head after delivery of
the head.
• It happens due to untwisting of the neck, which was twisted during
internal rotation.
• The head rotates one-eighth of a circle in the opposite direction of
the internal rotation.
35. External rotation
• External rotation is the visible movement of the fetal head seen after
restitution.
• It happens because of internal rotation of the shoulders inside the birth
canal.
• As the anterior shoulder rotates forward toward the symphysis pubis
(from the oblique diameter)
• After this movement, the shoulders align in the anteroposterior diameter
of the pelvis.
