Management of Normal and Abnormal Labors
Overview
 Gross & molecular structure of the myometrium and cervix
 Biochemical aspects of uterine contractions
 Birth canal
 Stages of labor
 Diagnosis, causes, & management of abnormal labor
Gross & molecular structure of the myometrium and
 smooth muscle surrounded by collagen and glycoaminoglycans
 cervix to fundus muscle component increases
o contractions strongest in fundus
 blood vessel course in between muscle fibers
o blood flow decreases during contractions
 fetal oxygenation
 post partum hemorrhage
Early Pregnancy
 few cellular contacts
 uncoordinated contractions
Late Pregnancy
 Placental estriol increases
o gap junctions
o electrical communications
o coordinated contractions
Cervix
 less smooth muscle
 collagen feels firm
Physiology of cervical ripening
 collagen fibers fractures
o proteolytic enzymes
o hyaluronic acid replaces glycosaminoglycans
o water content increases
o cervix softens, effacement begins, dilates
Regulators of cervical ripening
 Inhibitor
o progesterone
 Promoters
o estriol - oxytocin receptors
o relaxin
o oxytocin
o PGE1 and 2
o Laminaria rods
Physiology of uterine contractions
Inhibition of Uterine Contractions
Promotors of uterine contractions
 oxytocin

PGF2
o release of calcium from sarcoplasmic reticulum
 influx of calcium from Ca channels
Characteristics of the maternal birth canal
 Inlet
o sacral promontory
o linea terminalis
o posterior symphysis
Conjugates
 True - superior symphysis to sacral promontory
o not relevant to child birth
 Diagonal - inferior symphysis to sacral promontory
o clinical estimate of obstetrical conjugate (-1.5cm)
 Obstetrical - posterior symphysis to sacral promontory
o what the fetus passes through
Mid-pelvis
 sacrum
o hollow
 lateral
o ischial spines
 A-P = sagittal line
o inferior symphysis through bispinous diameter to sacrum
o anterior sagittal
o posterior sagittal
Outlet
 diamond shape
o mid symphysis
o 2 ischial tuberosities
o coccyx
Gynecoid pelvis
 round inlet
 hollow sacrum
 spines not prominent
o anterior sagittal > posterior
 occiput anterior presentations
 gentle curved symphysis
 most common type and best prognosis
Anthropoid pelvis
 African Americans
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oval inlet (A-P > transverse)
spines rotated anteriorly
anterior sagittal < posterior
occiput posterior
good prognosis (2nd stage longer)
Android
 whites
 heart-shaped inlet
 funnel shaped canal
 converging side walls
 straight sacrum
 prominent spines
 narrow symphysis
 poorest prognosis
Platyploid
 all planes are flat and oval
 Southeast Asians
 baby delivers transverse
 prognosis poor unless baby is small
7 cardinal fetal movements
 engagement
 descent
 flexion
 internal rotation
 extension
 external rotation
 expulsion
Stages of labor
 1st stage - onset of regular contractions to full dilation
o latent phase
o active phase
Latent phase
 0 to 4cm
 average = 14hr (Gravida 0), 8hrs (>Gravida 0)
 prolongation disorder = > 20hrs, 14hrs
Active phase
 4cm to complete dilation
 phase of maximum rate of dilation
 average = 1.2 cm/hr, 1.5 cm/hr
 arrest disorder = no dilation in 2 hrs

protracton disorder = slower than normal dilation
2nd stage
 full dilation to delivery
 descent disorder - presenting part does not descend
 prolonged 2nd stage
o without regional anesthesia
 > 2hrs, 1hrs
o with regional anesthesia
 > 3hrs, 2 hrs
Causes of abnormal labor
 poor uterine contractions
o 3-5 contractions every 10 min
o length of contractions = 60-90 sec
o strength = 25-100mmHg (requires pressure catheter)
o Montevideo units
 sum of all contractions in a 10 minutes period
 150-220 considered adequate
 Treatment = oxytocin (Pitocin)
Cephalopelvic disproportion (CPD)
 small pelvis
 fetal macrosomia (>4000 gm)
 abnormal fetal position
o occiput posterior
o military
o brow
o face (mentum posterior)
o non vertex presentation
 fetal anomalies (hydrocephaly, ascites)
Treatment of CPD
 Cesarean delivery
Putting it all together
 Active labor > 4cm
 Check every 2 hours in labor
 No progress of slow progress, evaluate contractions
o Palpation
o Pressure catheter
o Trial of oxytocin
 Prolonged 2nd stage
o > 2-3 hours
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Delivery options
o Operative vaginal (forceps or vacuum)
o Cesarean section
Watch for shoulder dystocia
Miscellaneous issue
 Neonatal group B Strep prophylaxis
o Penicillin G 5 million loading, 2.5 million q 4hr
o GBBS carrier
o Prolonged rupture of membranes (> 18hr)
o Maternal fever (> 380 C, 100.40F)
o Previous GBS infected baby