Labor

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Labor Delivery

• Anna Mae Smith, MPAS, PA-C
• Lock Haven University of Pennsylvania
• Physician Assistant Program

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Labor

• Physiologic process by which regularly occurring,
  uncomfortable-to-painful uterine contractions
  result in progressive effacement and dilatation
  of the cervix.
• This thinning out and dilatation permits passage
  of the fetus from the uterus through the birth
  canal, resulting in delivery.

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Onset cond

• increased synthesis of prostaglandins, which
  stimulate uterine contractions and which may
  soften the cervix independent of uterine activity
• an increase in myometrial oxytocin receptors,
  which amplify the biologic effect from a given
  amount of oxytocin

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First Stage

• Onset of uterine contractions as perceived by the
  pregnant woman and ends with complete or full
  dilatation of the cervix, which is 10 cm in
  diameter for a full-term infant
• Also called cervical stage

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Second Stage

• Begins with complete dilatation of the cervix and
  ends with delivery of the baby
• Also called pelvic stage

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Third Stage

• Begins with delivery of the baby and ends with
  delivery of the placenta and membranes
• Also called placental stage

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First Stage

• Active labor
• nullipara's cervix should dilate at least 1.2 cm
  per hour
• the cervix of a parous parturient should dilate
  at least 1.5 cm per hour

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EARLY LABOR

• Vary in frequency and intensity
• Typically, contractions occur every 5 to 10
  minutes (i.e., beginning of contraction to
  beginning of contraction
• Last for 30 to 45 seconds
• 20 to 30 mm Hg in intensity

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As labor proceeds, the contractions become more
frequent, more intense, and last longer. The
contractions occur every 2 to 3 minutes and last
for 50 to 70 seconds with a pressure or intensity
of 40 to 60 mm Hg.
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At full dilatation of the cervix, the parturient
perceives an urge to defecate. This sensation
reflects the descent of the fetus through the
birth canal that was made possible by the
retraction of the fully dilated cervix
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GETTING OUT

• The passage of the fetus through the pelvis is
  called the mechanism of labor, which usually
  takes place in a predictable sequence based on
  the mechanics of force from above and resistance
  from below

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Pelvis

• The bony pelvis consists of four bones
• sacrum
• coccyx
• two innominate bones, each made of the fused
  pubis, ischium, and ilium
• Babys head must go in an inferoposterior
  direction and then in an inferoanterior direction
  

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Cardinal Movements

• (1) engagement
• (2) descent
• (3) flexion
• (4) internal rotation
• (5) extension
• (6) external rotation
• (7) expulsion