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Physiology of delivery. Analgesia in labor.


Title: Labor Author: residents Last modified by: Created Date: 1/17/2008 7:47:36 PM Document presentation format: Company: Faculty of Medicine – PowerPoint PPT presentation

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Title: Physiology of delivery. Analgesia in labor.

Physiology of delivery. Analgesia in labor.
Korda I.
  • Labor is the physiologic process by which a fetus
    is expelled form the uterus to the outside world.
  • It involves the sequential integrated changes in
    the uterine decidua, and myometrium.
  • Changes in the uterine cervix tend to precede
    uterine contractions
  • Dilatation the enlarging of the cervix to 10
  • Effacement the thinning of the cervix. Your
    cervix starts out being two inches long, and 50
    effaced would be a 1 inch cervix.

Labor - Mechanics
  • Uterine contractions have two major goals
  • To dilate cervix
  • To push the fetus through the birth canal
  • Success will depend on the three Ps
  • Powers
  • Passenger
  • Passage

  • Uterine contractions
  • Power refers to the force generated by the
    contraction of the uterine myometrium
  • Activity can be assessed by the simple
    observation by the mother, palpation of the
    fundus, or external tocodynamometry.
  • Contraction force can also be measured by direct
    measurement of intrauterine pressure using
    internal manometry or pressure transducers.

  • There is no specific criteria for adequate
    uterine activity
  • Generally 3-5 contractions in a 10 minute period
    is considered adequate labor

  • Passenger fetus
  • Fetal variables that can affect labor
  • Fetal size
  • Fetal Lie longitudinal, transverse or oblique
  • Fetal presentation vertex, breech, shoulder,
    compound (vertex and hand), and funic (umbilical
  • Attitude degree of flexion or extension of the
    fetal head
  • Position
  • Number of fetuses
  • Presence of fetal anomalies hydrocephalus,
    sacrococcygeal teratoma

Cervical effacement and dilation
  • Station degree of descent of the presenting
    part of the fetus, measured in centimeters from
    the ischial spines in negative and positive
  • -5 is a floating baby,
  • 0 station is said to be engaged in the pelvis,
  • and 5 is crowning.

  • Passage Pelvis
  • Consists of the bony pelvis and soft tissues of
    the birth canal (cervix, pelvic floor
  • Small pelvic outlet can result in cephalopelvic
  • Bony pelvis can be measured by pelvimetry but it
    not accurate and thus has been replaced by a
    clinical trial of labor


The Stages of Labor
  • First Stage
  • Interval between the onset of labor and full
    cervical dilation
  • Two phases
  • Latent phase onset o f labor with slow cervical
    dilation to 4 cm and variable duration
  • Active phase faster rate of cervical change,
    1-1.2 cm /hour, regular uterine contractions

The Labor Curve
  • First stage - A latent phase B C D active
    phase B acceleration C maximum slope of
    dilation D deceleration E second stage.

  • Freidmans curve is a good guideline for expected
    progression in labor and therefore helpful to
    note abnormal labor patterns.

Labor NulliG MultiG
1st Stage Active phase
Duration 6-18 h 2-10 h
Dilation 1 cm/h 1.5 cm/h
Arrested gt2 h gt2h
2nd Stage 0.5-3 h 5-30 min
3rd Stage 0-30 min 0-30 min
Fig 1  An idealized labor pattern.  The normal
patterns of cervical dilation (solid line) and
descent (broken line) as they are traced against
elapsed time in labor. The distinctive phases of
the first stage are shown. The active phase
comprises the interval from the onset of the
acceleration phase to the beginning of the second
Labor Second Stage
  • Interval between full cervical dilation to
    delivery of the infant.
  • Characterized by descent of the presenting part
    through the maternal pelvis and expulsion of the
  • Indications of second stage
  • Increased maternal show
  • Pelvic/rectal pressure
  • Mother has active role of pushing to aid in fetal

Labor Second Stage
  • Molding is the alteration of the fetal cranial
    bones to each other as a result of compressive
    forces of the maternal bony pelvis.
  • Examining the fetal head during the second stage
    may become difficult due to molding
  • Caput is the localized edematous area on the
    fetal scalp caused by pressure on the scalp by
    the cervix.
  • PrimiG 0.5-3 h mulitG 0-30min

  • Suctioning the nasopharynx
  • Cut between the clamps
  • Clamp the umbilical cord

Labor Third Stage Placental separation and
  • The time from fetal delivery to delivery of the
  • Signs of placental separation
  • a. The uterus becomes globular in shape and
  • b. The uterus rises in the abdomen.
  • c. The umbilical cord descends three (3) inches
    or more further out of the vagina.
  • d. Sudden gush of blood.

Labor Third Stage
  • Placenta is delivered using one hand on umbilical
    cord with gentle downward traction. Other hand on
    abdomen supporting the uterine fundus.
  • Risk factor for aggressive traction is uterine
  • Obstetrical emergency!!
  • Normal duration between 0-30 min for both PrimiG
    and MultiG

  • Inspect the placenta for completeness

(No Transcript)
  • AMTSL Active management of third stage of
    labour. RP retained placenta. CCT controlled
    cord traction. Hb Haemoglobin. BP Blood
    pressure. MRP Manual removal of placenta. Hb

Labor Fourth Stage
  • Refers to the time from delivery of the placenta
    to 1 hour immediately postpartum
  • Blood pressure, uterine blood loss and pulse rate
    must be monitor closely 15 minutes
  • High risk for postpartum hemorrhage from
  • Uterine atony, retained placental fragments,
    unrepaired lacerations of vagina, cervix or
  • Occult bleeding may occur vaginal hematoma
  • Be suspicious with increased heart rate, pelvic
    pain or decreased BP!!!!!!

Cardinal Movements of Labor
  • This refers to the movements made by the fetus
    during the first and second stage of labor. As
    the force of the uterine contractions stimulates
    effacement and dilatation of the cervix, the
    fetus moves toward the cervix.
  • When the presenting part reaches the pelvic
    bones, it must make adjustments to pass through
    the pelvis and down the birth canal

Seven distinct movements
  • Engagement
  • Descent
  • Flexion
  • Internal rotation
  • Extension
  • External rotation/restitution
  • Expulsion

Cardinal Movements of Labor
  • Engagement
  • Passage of the widest diameter fetal presenting
    part below the plane of the pelvic inlet
  • The head is said to be engaged if the leading
    edge is at the level of the ishial spines.
  • Descent
  • Refers to the downward passage of the presenting
    part through the bony pelvis
  • Not steady process
  • Greatest at deceleration phase of first stage and
    during 2nd stage of labor

Cardinal Movements of Labor
  • Flexion
  • Occurs passively as the head descends due to the
    shape of the bony pelvis.
  • Partial flexion occurs naturally but complete
    flexion usually occurs only in the labor process
  • Complete flexion places the fetal head in optimal
    smallest diameter to fit through the pelvis
  • Internal Rotation
  • Rotation of the fetal head from occiput
    transverse to occiput either in anterior or
    posterior position
  • Occurs passively due to the shape of the bony

Cardinal Movements of Labor
  • Extension
  • Occurs when the fetus has descended to the level
    of the vaginal introitus
  • When occiput is just past the level of the
    symphysis, the angle of the birth canal changes
    to upward position
  • External Rotation/Restitution
  • As the head is delivered, it rotates back to its
    original position prior to internal rotation
  • It aligns anatomically with the fetal torso
  • The release of the passive forces on the fetal
    head allows it to return to appropriate position

  • Delivery of the fetus
  • After delivery of the fetal head, descent and
    intraabdominal pressure by mother brings shoulder
    to the level of the symphysis
  • Downward traction allows release of the shoulder
    and the fetus is delivered.

Analgesia in labor Discomfort during Labor and
  • Pain and discomfort experienced during labor have
  • two neurologic origins visceral and somatic
  • Neurologic origins
  • Visceral pain from cervical changes, distention
    of lower uterine segment, and uterine ischemia
  • Located over the lower portion of abdomen
  • Referred pain originates in uterus, radiates to
    abdominal wall, lumbosacral area of back, iliac
    crests, gluteal area, and down the thighs
  • Somatic pain pain described as intense, sharp,
    burning, and well localized
  • Stretching and distention of perineal tissues and
    pelvic floor to allow passage of fetus, from
    distention and traction on peritoneum and
    uterocervical supports during contractions, and
    from lacerations of soft tissue

Perception of pain
  • Threshold remarkably similar in all, regardless
    of gender, social, ethnic, or cultural
  • Differences play definite role in persons
    perception of and behavioral responses to pain

Expression of pain
  • Pain results in physiologic effects and sensory
    and emotional (affective) responses
  • Emotional expressions of suffering often seen
  • Increasing anxiety
  • Writhing, crying, groaning, gesturing (hand
    clenching and wringing), and excessive muscular
  • Cultural expression of pain varies

Factors influencing pain response
  • Physiologic factors
  • Culture
  • Anxiety
  • Previous experience
  • Childbirth preparation
  • Comfort and support
  • Environment

Distribution of labor pain
  • A. Distribution of labor pain during first stage
  • B. Distribution of labor pain during later phase
    of first stage and early phase of second stage
  • C. Distribution of labor pain during later phase
    of second stage and during birth
  • (Gray shading indicates areas of mild
    discomfort light-colored shading indicates
    areas of moderate discomfort dark-colored shadin
    g indicates areas of intense discomfort.)

Nonpharmacologic Management of Discomfort
  • Nonpharmacologic measures often simple, safe, and
  • Provide sense of control over childbirth and
    measures best for woman
  • Methods require practice for best results
  • Try variety of methods and seek alternatives,
    including pharmacologic methods, if measure used
    is not effective

Nonpharmacologic Management of Discomfort
  • Childbirth education
  • Dick-Read method
  • Lamaze method
  • Bradley method
  • Relaxing and breathing techniques
  • Relaxation
  • Imagery and visualization
  • Music
  • Touch and massage
  • Breathing techniques
  • Effleurage and counterpressure
  • Water therapy (hydrotherapy)
  • Transcutaneous electrical nerve stimulation

Pharmacologic Management of Discomfort
  • Nerve block analgesia and anesthesia
  • Local perineal infiltration anesthesia
  • Prudendal nerve block
  • Spinal anesthesia (block)
  • Disadvantages
  • Medication reactions (allergy)
  • Hypotension
  • Ineffective breathing
  • Headache
  • Autologous epidural blood patch
  • Sedatives
  • Analgesia and anesthesia
  • Anesthesia
  • Systemic analgesia
  • Opioid agonist analgesics
  • Opioid (narcotic) agonistantagonist analgesics
  • Co-drugs
  • Ataractics
  • Opioid (narcotic) antagonists

Pain Pathways and Sites of Pharmacologic Nerve
  • A. Pudendal block suitable during second and
    third stages of labor and for repair of
  • B. Epidural block suitable during all stages
    of labor and for repair of episiotomy

Pain Pathways and Sites of Pharmacologic Nerve
  • Nerve block analgesia and anesthesia
  • Epidural anesthesia/analgesia
  • Lumbar epidural anesthesia/analgesia
  • Walking epidural analgesia
  • Epidural and intrathecal opioids

  • Membranes and spaces of spinal cord and levels
    of sacral, lumbar, and thoracic nerves
  • Cross section of vertebra and spinal cord

Levels of Anesthesia Necessary for Cesarean and
Vaginal Births
Care Management
  • Plan of care and interventions (contd)
  • Administration of medication
  • Intravenous route
  • Intramuscular route
  • Spinal nerve block
  • Signs of potential problems
  • Safety and general care
  • Anesthesia in the obese woman

Key Points
  • Expected outcome of preparation for childbirth
    and parenting is education for choice
  • Nonpharmacologic pain and stress management
    strategies are valuable for managing labor
    discomfort alone or in combination with
    pharmacologic methods
  • Gate-control theory of pain and stress response
    are bases for many of the nonpharmacologic
    methods of pain relief
  • Type of analgesic or anesthetic used is
    determined in part by stage of labor and method
    of birth
  • Opioid effects can be potentiated with ataractics

In Summary
  • Know the different stages of labor
  • Know the labor curve
  • Know the cardinal movements of labor
  • Know the causes of postpartum hemorrhage
  • MD must understand medications, expected effects,
    potential adverse reactions, and methods of
  • Maternal fluid balance is essential during spinal
    and epidural nerve blocks
  • Maternal analgesia or anesthesia potentially
    affects neonatal neurobehavioral response
  • Use of opioid agonist-antagonist analgesics in
    women with preexisting opioid dependence may
    cause symptoms of abstinence syndrome (opioid
  • General anesthesia rarely used for vaginal birth
  • May be used for cesarean birth or when needed in
    emergency childbirth situation

Thank you for your attention!