questions 7

Intrapartum Fetal Assessment

Topic updated on 11/30/17 2:02pm

  • A 35-year-old woman at 42 weeks of gestation presents for an induction of labor due to postterm pregnancy. She reports positive fetal movement, and denies vaginal bleeding. After amniotomy is performed, a change in fetal heart monitor is noted. Maternal repositioning is performed. (Variable decelerations)
Biophysical Profile (BPP)
  • Five measurements of fetal well being, each rated on scale of 1-2
    • measure
      • fetal breathing
      • gross body movements
      • fetal tone
        • extremity extension and flexion
      • amniotic fluid volume
      • nonstress test (NST)
  • Scoring
    • 8-10 is reassuring
    • 6 is equivocal
      • delivery if > 36 weeks
      • repeat BPP in 24 hours if < 36 weeks
    • ≤ 4 is abnormal
      • requires immediate intervention 
Fetal Heart Rate (FHR)
  • Normal FHR 120-160/min
  • Tachycardia is FHR > 160/min
    • causes include
      • maternal fever
      • fetal hypoxia
      • prematurity
      • anemia (maternal or fetal)
      • chorioamnionitis
      • hyperthyroidism
  • Bradycardia is FHR < 110/min for > 10 minutes
    • causes include
      • congenital heart block
      • maternal β-blockers
  • FHR variability
    • reliable indicator of fetal well being
    • causes of decreased variability include
      • fetal hypoxia
      • congenital heart anomalies
Electronic Fetal Heart Rate Monitoring (EFM) Tracing Interpretation
  • Accelerations
    • FHR at least 15/min above baseline for 15 seconds in a 20 minute period
      • considered a reactive NST (needs the presence of at least 2 accelerations)  
    • suggests fetal well being
  • Early decelerations
    • FHR (not below 100/min) that coincide with uterine contraction
    • results from pressure on fetus head resulting in vagus nerve stimulation and reflex bradycardia
    • physiologic and not harmful to fetus  

  • Variable decelerations
    • may not coincide with uterine contractions
    • rapid in FHR (often < 100/min) with variable recovery
    • reflex mechanism due to umbilical cord compression
      • rupture of membrane can lead to umbilical artery compression
    • correct by shifting maternal position or amnioinfusion if membranes ruptured
      • considered first-line
      • if maternal repositioning does not improve FHR tracing, amnioinfusion can be considered

  • Late decelerations
    • begins after uterine contraction has started
    • associated with uteroplacental insufficiency and viewed as potentially dangerous 
    • causes include
      • placental abruption
      • maternal diabetes
      • maternal anemia
      • maternal sepsis
      • postterm pregnancy
      • hyperstimulated uterus
    • repetitive late develerations require intervention

  • Sinusoidal tracing
    • sine-wave like pattern
    • associated with increased morbidity and mortality
    • indicative of severe fetal anemia
      • e.g., severe hypoxia and Rh disease



Qbank (2 Questions)

(M2.OB.195) A 29-year-old G2P1001 female at 39 weeks' gestation presents to labor and delivery triage with intermittent lower abdominal pain and concern for decreased fetal movement over the last 18 hours. A tocometer and doppler fetal heart monitor are placed on the patient's abdomen. The fetal heart rate monitoring strip depicted in Figure A is obtained. Which of the following physiologic processes is responsible for the pattern seen on the fetal heart rate tracing in this patient? Topic Review Topic
FIGURES: A          

1. Compression of the umbilical cord
2. Uteroplacental insufficiency
3. Fetal anemia secondary to Rh disease
4. Oligohydramnios
5. Fetal vagal response to head compression by uterine contractions

(M2.OB.196) A 32-year-old G4P2103 at 39 weeks gestation presents to the emergency department stating that her "water broke" one hour ago. The patient is placed on tocometry and electronic fetal heart monitoring (Figure A). Which of the following is the most likely direct cause of this fetal heart rate pattern? Topic Review Topic
FIGURES: A          

1. Uteroplacental insufficiency
2. Oligohydramnios
3. Fetal head compression
4. Umbilical cord compression
5. Spontaneous rupture of membranes

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