Normal Pregnancy 3

Question 1

What are the mechanisms that result in parturition?

Answer 1

• Ultimately remain unelucidated in humans
• Myometrial contractility
  
  • Smooth muscle contractions mediated through ATP=dependent binding of myosin to actin
  • Frequency of contractions corresponds to frequency of action potentials
  • Force of contractions mediated by numbers of fibers activated

Question 2

Describe the power involved in labor.

Answer 2

• Strength of contraction and appropriate frequency of contractions
• Optimally 3-5 contractions in 10 minute period
• External versus internal monitoring
• Main mechanics of labor that can be affected by medical management

Question 3

What are some important aspects regarding the passenger during labor and delivery? Discuss lie, presentation, position, and station of the fetal attitude.

Answer 3

• Fetal size in relation to maternal pelvis impacts success of labor
• Fetal attitude
  
  • Lie: Long axis of fetus in relation to maternal long axis
    
    • Longitudinal, transverse, oblique
  • Presentation: Pole of the fetus that overlies pelvic inlet
    
    • Cephalic, breech
  • Position: Relationship of fetal presenting part to maternal pelvis
    
    • E.g. Occiput anterior, occiput posterior, mentum anterior, mentum posterior
  • Station: Position of leading bony edge of presenting fetal part to maternal ischial spines
    
    • 3 or 5-point scale
    • Position of leading bony edge of presenting fetal part to maternal ischial spines

Question 4

What are the shapes of the passage that could affect labor and delivery?

Answer 4

• Shape determined by the maternal bony pelvis: Sacrum, ilium, ischium, pubis
• Pelvic shapes
  
  • Antropoid
  • Android
  • Platypelloid
  • Gynecoid​
• Pelvic muscles facilitate rotation and delivery

Question 5

What are the stages of labor? Briefly describe each one.

Answer 5

• Stage 1: Interval between onset of labor and full cervical dilation
  
  • Latent
    
    • Onset of painful contractions to point of change in slope of labor curve (usually 6cm)
    • Duration varies
  • Active
    
    • Period of rapid cervical change
    • Anticipate at least 1.2 cm change/hr for nulliparas and 1.5 cm change/hr for multiparas
• Stage 2: Interval between full cervical dilation and delivery of fetus
  
  • Can last up to 4 hours in nulliparas with epidural analgesia (3 hours without) and 3 hours in multiparas with epidurals (2 hour without)
• Stage 3: Interval between delivery of neonate to delivery of placenta
  
  • Usually occurs within 10 minutes of delivery, but up to 30 minutes is normal

Question 6

What are the cardinal movements in labor and delivery?

Answer 6

• Engagement
• Flexion
• Descent
• Internal rotation
• Extension
• External rotation
• Expulsion