Parturition/Stages%20of%20Labor

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Parturition/Stages of Labor

• Methodius Tuuli, MD, MPH
• Division of Maternal-Fetal Medicine

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(No Transcript)
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Objectives

• Describe physiology of labor
• Define stages of labor
• Discuss concepts of normal labor progress
• Traditional (Friedmans)
• Contemporary (Zhangs)
• Custom labor curve (Cahill/Tuuli)

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PARTURITION
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Parturition

• Early Pregnancy
• Uterine quiescence
• Closed cervix
• Parturition
• Coordinated uterine activity
• Cervical remodelling
• Progressive cervical dilation

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Mediators of Uterine Activity

• Inhibitors
• Progesterone
• Prostacycline
• Relaxin
• Nitric Oxide
• Parathyroid hormone-related peptide
• CRH
• HPL
• Quiescence

Uterotonins Prostaglandins Oxytocin Stim
ulation

• Uterotrophins
• Estrogen
• Progesterone
• Prostaglandins
• CRH
• Activation

• Involution
• Oxytocin
• Thrombin
• Involution

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Initiation of Labor

• Fetus
• Sheep
• Fetal ACTH and cortisol
• Placental 17 a hydroxylase
• ? Estradiol
• ? Progesterone
• Placental production of oxytocin, PGF2 a
• Humans
• Fetal increased DHEA
• Placental conversion to estradiol
• Increased decidual PGF2 and gap junctions
• Increased oxytocin and PG receptors
• Changes in progesterone receptors

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Initiation of Labor

• Oxytocin
• Peptide hormone
• Hypothalamus-posterior pituitary
• Oxytocin receptors
• Fundal location
• 100-200 x during pregnancy
• Actions
• Stimulate uterine contractions
• Stimulate PG production from amnion/decidua

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Oxytocin receptor
Extracellular
Calcium channel
Intracellular
Phospholipase C
cAMP
Ca
MLCK
Ca store
Oxytocin Prostaglandin
Uterine contractions
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Labor
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Labor

• Regular uterine contractions
• and
• Progressive cervical dilatation

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Labor

• Cervical effacement
• Cervical dilatation

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Labor the three Ps

• Passage
• Passenger
• Powers

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Passage
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Passenger

• Size
• Estimated fetal weight
• Lie
• Longitudinal
• Transverse/oblique
• Presentation
• Vertex 95
• Non-vertex 5
• Station
• Position

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Passenger cardinal movements of labor

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

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Powers

• Uterine contractions
• Duration 30-60 seconds
• 3-5 contractions / 10 minutes
• Montevedeo units (intrauterine catheter)
• Baseline to peak
• Sum over 10 minutes
• Adequate gt200-250 MVU

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Labor Progress
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Stages of Labor

• First stage onset of labor to complete
  dilatation
• Latent phase
• Active phase
• Second stage complete cervical dilation to
  expulsion of fetus
• Third stage expulsion of fetus to expulsion of
  placenta
• (Fourth Stage First hour after expulsion of
  placenta)

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Labor Curve
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First Stage

• Latent phase onset to rapid cervical change
• Active phase rapid cervical change to complete
  dilatation
• Traditional standards

Nulliparous Nulliparous Multiparous Multiparous
Mean 95th tile Mean 95th tile
Latent phase 7.3-8.6hr 17-20 hr 4.1-5.3hr 12-14 hr
Active phase 1.5cm/hr 1.2cm/hr
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Second Stage

• Traditional standards
• Immediate versus delayed pushing
• Spontaneous versus coached pushing

Nulliparous Nulliparous Multiparous Multiparous
Mean 95th tile Mean 95th tile
No epidural 53-57 min 122-147 min 17-19 min 57-61 min
Epidural 79 min 185 min 45min 131min
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Third Stage

• Standards
• Mean 6 minute
• 97th tile 30 minutes
• Active versus passive

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CHANGING LABOR STANDARDS
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Why concern?

• Too many cesarean

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Why concern?
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1955 Friedmans Labor Curve

• Convenience sample
• 622 consecutive nullips
• 500 with adequate data
• Cervical dilation (Y) plotted against time (X)
• Major advance in his day
• ..introduces a new dimension to us. Evaluation
  of progress, previously synonymous with nebulous
  degree of change, becomes available to us in
  terms of specific change.

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Traditional labor curve Friedmans
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Limitations of Friedmans Curve

• Non-representative sample
• More graphical than statistical
• Did not take into account special characteristics
  of labor data
• Adopted without complete context
• Subject characteristics
• Interventions

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2002 Zhangs Labor Curve

• Took into account the unique features of labor
  data
• Left censored
• Interval censored
• Repeated measures
• Log-normal distribution
• Appropriate analytical tools
• Repeat ed measures regression ?curves
• Interval censored regression models ?medians
  (95th tile)
• Contemporary sample

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2002 Zhangs Labor Curve
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2002 Zhangs Labor Standard
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Zhangs curve key concepts

• Transition to active labor after 6cm dilation
  not 4cm.
• No deceleration phase
• Traverse times
• much longer in latent phase
• much shorter in active phase

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TOWARDS CUSTOM LABOR STANDARDS
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Does one size fit all? Fetal Size
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Does one size fit all? Fetal Sex
Cahill AG, Roehl KA, Odibo AO, Zhao Q, Macones
GA. Am J Obstet Gynecol. 2012 Apr206(4)335.e1-5.

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Does one size fit all? Maternal Race
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Does one size fit all? Induced labor
Harper LM, Caughey AB, Odibo AO, Roehl KA, Zhao
Q, Cahill AG. Obstet Gynecol. 2012
Jun119(6)1113-8.
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Does one size fit all? Induction method
Tuuli MG, Keegan MB, Odibo AO, Roehl K, Macones
GA, Cahill AG. Am J Obstet Gynecol. 2013
Sep209(3)237.e1-7.
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Does one size fit all? Maternal Obesity
Norman SM, Tuuli MG, Odibo AO, Caughey AB, Roehl
KA, Cahill AG. Obstet Gynecol. 2012
Jul120(1)130-5.
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Custom Labor Curve the Holy Grail

• Seeks to incorporate the multiplicity of
  individual patient factors in estimating expected
  labor progress
• Has been methodologically challenging
• Recent progress
• N5000
• Detailed labor data
• Collaboration with statisticians
• Mathematical model incorporating
• Parity
• Epidural
• BMI
• Labor type

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Custom Labor Curve the Holy Grail
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Custom Labor Curve the Holy Grail

• Next steps
• Validate in independent data set (N4000)
• Refine model to include time variable factors
• Software development
• RCT to assess impact on cesarean rate

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Summary

• Labor involves transition of the uterus from a
  quiescent state to regular contractions and
  cervical dilation resulting in delivery of the
  fetus and placenta
• Initiation of labor in humans is incompletely
  understood, but involves maternal-fetal-placental
  interactions

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Summary

• Clinical management of labor requires
  understanding of the normal progress
• Our understanding of normal progress of labor is
  evolving towards more customized individualized
  standards

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Questions