The course and conduct of normal labor and delivery

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The course and conduct of normal labor and
delivery

• Emilia Brzezinska
• Division of Perinatal Medicine

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A definition of labor

• Progressive dilatation of the uterine cervix in
  association with repetitive uterine contractions.
• Spontaneous or induced
• Term or preterm

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Important terms

• Lie- relationship between the long axis of the
  fetus and that of the mother (longitudinal,
  transverse or oblique).
• Presentation- the fetal part that lies closest to
  the pelvic inlet (cephalic - vertex, face
  breech shoulder).
• Attitude- relationship of the fetal parts to each
  other, usually head and trunk (flexion or
  extension of the neck).

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Onset of labor

• Regular uterine contractions - from at least 1/2
  hr, frequency at least every 10 minutes
• Bleeding
• Rupture of membranes

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Stages of the labor

• I - shortening and dilatation of the cervix
• II - delivery of the fetus
• III - delivery of the placenta with the umbilical
  cord and membranes
• IV - about two hours after delivery (inspection
  and surgical help)

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Duration of the labor
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Dilatation of the cervix

• Nullipara
• I - shortening
• II - dilatation of external os
• III - dilatation of internal os
• Multipara
• phases I, II and III occur together

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Mechanisms of labor

• The special labor mechanisms is due to asymmetry
  of the shape of both the fetal head and maternal
  pelvis.
• Changes in the position of the fetal head are
  required for the average size fetus to accomplish
  passage through the birth canal.
• The rotations are accomplished by the propulsive
  force of uterine activity.

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Important!

• Pelvic planes and diameters of the pelvic inlet
• Diameters of fetal skull
• Leopolds maneuvers
• (Data in each manual of obstetrics)

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Examination

• External (Leopolds maneuvers)
• Internal
• cervix - length and dilatation
• membranes - intact or not, color of the amniotic
  fluid
• fetus - presentation, attitude, rotation
• pelvis - size

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Cardinal movements of labor

• movements of the head

• engagement
• descent
• 1. flexion
• 2. internal rotation
• 3. extension
• 4. external rotation
• expulsion

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Engagement

• It is the descent of the largest transverse
  diameter of fetal head (BPD) to a level below the
  plane of the pelvic inlet.
• Then the head is engaged.

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• Flexion (I? movement of the head) - placement of
  the fetal chin on the thorax
• Internal rotation (II? movement) - rotation from
  the transverse position towards symphysis.

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Extension - III ? movement

• Begins at the level of maternal vulva
• The fetal head is delivered by extension from the
  flexed to the extended position rotating around
  the symphysis pubis

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External rotation - IV ? movement

• After delivery of the head the forces exerted on
  the head by the maternal pelvic musculature are
  relived and the fetus resumes its normal
  face-forward position.
• Its face begins to look at one of mothers leg.

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Expulsion

• Delivery of the shoulders - first the anterior
  one (under the symphysis pubis) and then the
  posterior one.
• The rest of the body is usually quickly delivered.

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Assisted spontaneous delivery

• Lateral episiotomy
• Prevention of rapid delivery of the head
• Delivery of the shoulders and body
• Aspiration of the mucus from the fetal mouth,
  pharynx and nose
• Cord clamping

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Episiotomy

• A lateral incision of perineum before delivery of
  the head
• Why?
• to enlarge the area of the outlet ? easier
  delivery of the head ? prevention of
  intraventricular hemorrhage
• prevention of lacerations
• prevention of late complications - relaxation of
  pelvic muscles and urine incontinence

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Episiotomy

• Prophylactic - nulliparas, some multiparas
• Mandatory
• in instrumental delivery, like forceps or vacuum
  extractor
• in abnormal presentations, like breech
• in preterm deliveries

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Monitoring of fetal well-being

• Continuous fetal heart rate and contractions
  monitoring (CTG) - external or direct
• baseline FHR
• FHR variability
• periodic FHR changes
• decelerations (early, late, variable)
• accelerations
• sinusoidal FHR pattern
• Fetal capillary scalp blood sampling

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Baseline FHR

• between 110 and 150 bpm
• lt 100 - bradycardia (e.g. hypoxia)
• gt 160 - tachycardia (e.g. infection)

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FHR variability

• short-term, a beat-to-beat variability
• normal ranges 5 - 20 bpm from the basis
• lt 5 - loss of variability (silent)
• gt 25 - exaggerated variability

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Deceleration

• Decrease in FHR of at least 15 bpm lasting 15 s
  or longer
• early - begins with the beginning of contraction,
  reaches its lowest point just with the peak of
  contraction
• late - occurs in the late phase of contraction,
  its lowest point is after contraction
• variable - no association with contractions

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Deceleration

• early - due to pressure of fetal head as it moves
  down the birth canal, reflex mediated by the
  vagus nerve
• late - result of fetal hypoxia (uteroplacental
  insufficiency)
• variable - effect of umbilical cord compression
  (cord around the neck, arm or between some part
  of the fetus and the uterine wall)

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Acceleration

• Increase in FHR of at least 15 bpm lasting 15 s
  or longer
• associated with contractions or fetal movements
• indicator that fetus is adequately oxygenated

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Anesthesia for labor

• Psychoprophylaxis - very important
• teaching about physiology
• breathing
• stress control
• husband participation
• Narcotic drugs - attention risk of respiratory
  depression in newborn
• Subarachnoidal block

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