Normal labor

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Normal Labor

Definition
• The series of the events that takes place from
the uterine contraction to the expulsion of
placenta normally.

Stages of Labor
• Four stages
1. First stage of labor
a. Latent Phase
b. Active Phase
2. Second stage of Labor
3. Third stage of Labor
4. Fourth stage of Labor

First Stage of Labor
• Begins with onset of
regular uterine
contraction
• Ends with complete
cervical dilation at 10
cm

Latent Phase
• Contractions become progressively stronger
longer and more frequent and better
coordinated
• Cervix effaces but shows minimal dilation
• Duration:
(May be intermittent over several days or may last only
few hours)
– Nulliparas: Average 8 hours
– Multiparas: Average 5 hours

Active Phase
• Cervix dilates usually from 3-4 cm to full
dilation i.e. 10 cm
• Duration more predictable
• Duration and Rates
– Nullipara: 5 hours; 1.2 cm/hour
– Multipara: 2 hours; 1.5 cm/hour

Second Phase
• Begins with
complete cervical
dilation
• Ends with delivery
of the baby

Third Stage
• Begins with the delivery of
baby
• Ends with delivery of placenta
• Placenta separation from
uterine wall occurs as the
result of myometrium
contraction shear off
anchoring villi
• Duration:
– <30 minutes in all women

Fourth Stage
• First one hour after delivery
• Vital signs and any evidence of uterine atony
or postpartum hemorrhage
• Perineum inspection for any signs of
hematoma formation
• Mother should be seen every 15 mins
• Newborn undergoes initial assessment

Cardinal Movement of Labor
1. Engagement
2. Descent
3. Flexion
4. Internal Rotation
5. Extension
6. External Rotation
7. Expulsion

Engagement
• Movement of the
presenting part below the
plane of the pelvic inlet
• Engaging process start at
the last few weeks of
pregnancy to the period of
starting of labor

Descent
• Movement of presenting
part down through the
curve of the birth canal
• Result of :
– Pressure of amniotic fluid
– Direct pressure of the fundus
upon the breech with
contraction
– Bearing down effect of maternal
abdominal muscle
– Extension and straightening of
fetal body

Flexion
• Placement of fetal
chin on the thorax
• Result from resistant
of cervix , wall of
pelvis or pelvic floor

Internal Rotation
• Rotation of the position
of the fetal head in the
mid pelvis from
transverse to anterior-
posterior
• Essential for the
completion of labor

Extension
• Movement of fetal chin
away from the thorax as it
reaches to vulva
• Forces acting:
– First force-exerted by uterus -
acts posteriorly
– Second force by resistant pelvic
floor and symphysis- acts
anteriorly
(Resultant vector is in the
direction of vulvar opening,
causing extension)

External Rotation(Restitution)
• Rotation of the fetal head
outside the mother as the
head passes through the
pelvic outlet
• One shoulder is anterior
behind the symphysis and
other is posterior due to
external rotation

Expulsion
• Delivery of fetal
shoulders and body

Fetal Skull
Figure. Fetal skull from lateral view

Figure. Fetal skull superior view

Diameter of fetal skull(Lateral view)

Diameter of fetal skull(Superior view)

Abnormal fetal head presentation
• Face Presentation
• Brow Presentation

Face presentation
• The head is hyperextended so that the occiput is in
contact with the fetal back, and the chin is present
• Causes include
– Preterm infant with smaller head dimension
– Enlargement of neck due to coiling of the cord
– Anencephalic fetus naturally present with this
• Diagnosis
– The radiographic demonstration of the hyper extended head
with facial bone at or below the pelvic inlet(characterstic)

Brow Presentation
• Diagnosed when the portion of the fetal head
between the orbital ridge and anterior fontanel
presents at pelvic inlet
• Causes:
• Same as face presentation
• Usually on vaginal examination the frontal suture,
large anterior fontanel orbital ridges and root of
the nose are felt but never mouth and chin is
palpable

Abnormal labour
• Shoulder dystocia
Means difficult labor: slow labor
progress
Causes
1.Uterine contraction problem
2.Abnormal presentation, position
3.Contracted bony pelvis
4.Soft tissue obstruction
i.e. power, passenger and passage’s
problem

 Prolonged latent phase: N:>20hr M:>14hr
 Protracted disorder: active phase: N: <1.2cm/hr M:<1.5cm/hr for more than
4 hr
Descent: N: <1cm/hr M:<2cm/hr
 Arrest disorder: failure of descent, no dilation for 2hr
 To call protracted or arrest, cervical dilatation should be >3 or 4cm
Fundus and cervix has different intensity and time differential in onset of
contraction.
Uterine dysfunction:
1. hypotonic: synchronous but less powerful contraction
2. Hypertonic or incoordinated: gradient distortion present
Cause: chorioamnionitis, epidural analgesia, back lying of mother,
First stage disorder: uterine dysfunction mainly
2nd stage disorder: obvious for passage and passenger disproportion
High station is also a risk factor for dystocia

 Precipitous labor: expulsion of fetus in <3hr (cervical dilatation: N: >5cm/hr
M:>10cm/hr
 No complication occur when cervix dilated, vagina stretched and perineum
relaxed. If not then uterine rupture or severe injury to birth canal can occur.
Amnionic fluid embolism can also occur.
 much Chance of uterine atony- PPH
 Fetal effect: hematoma, anoxia due to contracted uterus, erb palsy or
Duchenne brachial palsy
 Ttmnt: tocolytics such as Mag salt
Fetopelvic disproportion:
 due to contracted pelvis: if shortest AP distance <10cm and transverse <12cm

References
• Kevin p. Henretty. Obstratics Anatomy. Obstetrics illustrated.
Churchill Livingstone. Elsiver. Page no. 54-5.
• Oxford Handbook of Clinical Specialties, 5th edn (ed. Collier J,
Longmore M, Brown TD), p. 87.
• Rouse, Hauth, et.al. William Obstetrics. 23rd Edition. Normal
Labour.

Thank You!

Normal labor

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