OnExam

The Sign and its Interpretation

  1. Can be continuous or periodic, external or via scalp electrode
  2. Baseline FHR should be 110-160bpm
  3. Variability is described as absent, minimal (less than 5bpm), moderate (6-25bpm) or marked (more than 25bpm). Normal variability is moderate
  4. Acceleration:
    • Before 32 weeks = peak more than 10bpm above baseline with a duration of more than 10s but less than 2 mins
    • After 32 weeks= peak more than 15bpm above baseline with a duration of more than 15s but less than 2 mins
    • A normal FHR will have at least 2 accelerations in 20 minutes
  5. Deceleration:
    • Can be early, late or variable
    • Early: associated with a uterine contraction, gradual onset to nadir >30s, nadir of deceleration at same time as peak of contraction
      • Physiological finding hypothesized to be related to fetal head compression
    • Late: Onset, nadir and recovery of deceleration occur after the beginning, peak and end of contraction respectively
      • Compromised uteroplacental perfusion
      • Intervention may be needed
    • Variable: deceleration not related to contraction
      • The most common type of deceleration
      • Related to umbilical cord compression

References

  1. Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Rouse DJ, Spong CY. Williams Obstetrics. 23rd ed. New York: McGraw-Hill; 2010.
  2. Swesha A, Hacker TW, Nuovo J. Interpretation of the electronic fetal heart rate during labor. Am Fam Physician. 1999; 59(9) 2487-2500