OnExam
- Fetal Heart Rate (FHR) Monitoring
The Sign and its Interpretation
- Can be continuous or periodic, external or via scalp electrode
- Baseline FHR should be 110-160bpm
- Variability is described as absent, minimal (less than 5bpm), moderate (6-25bpm) or marked (more than 25bpm). Normal variability is moderate
- 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
- 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
- Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Rouse DJ, Spong CY. Williams Obstetrics. 23rd ed. New York: McGraw-Hill; 2010.
- Swesha A, Hacker TW, Nuovo J. Interpretation of the electronic fetal heart rate during labor. Am Fam Physician. 1999; 59(9) 2487-2500