II. Definitions
- Variable Deceleration
- Variable in relation to contraction
- Variable shape of deceleration
- Abrupt onset and return (steep slope of change)
- Contrast with other decelerations
- Associated with small acceleration
- Onset of Variable Deceleration to nadir < 30 seconds
- Heart Rate decrease >=15 bpm
- Variable Deceleration Duration 15 seconds to 2 minutes
III. Physiology
- Variable Decelerations are a result of cord compression
- Often benign if mild deceleration in active labor
- May represent uteroplacental insufficiency for some
IV. Grading: Variable Decelerations
- Mild Variable Deceleration
- Variable Deceleration <30 seconds
- Fetal Heart Rate 80-120 bpm
- Fetal Heart Rate 70-120 bpm for <60 seconds
- Moderate Variable Deceleration
- Fetal Heart Rate <70 bpm for 30-60 seconds
- Fetal Heart Rate 70-120 bpm for >60 seconds
- Severe Variable Deceleration
- Fetal Heart Rate <70 bpm for >60 seconds
V. Interpretation
- More reassuring
- Acceleration just before variable ("Shoulder")
- Good baseline variability
- Rapid descent and recovery
- Non-Reassuring
- Repetitive severe decelerations
- Fetal Heart Rate <70 bpm for >60 seconds
- Occurs repeatedly over 20 minute observation
- Loss of "Shoulder" accelerations
- Loss of short-term variability
- Slow recovery from deceleration
- Baseline Tachycardia
- Repetitive severe decelerations
VI. References
- Bailey (2000) ALSO, E:1-13
- Gabbe (2002) Obstetrics, p. 395
- Arnold (2020) Am Fam Physician 102(3): 158-67 [PubMed]
- Rylander (2001) Clin Fam Pract 3(2):287-305 [PubMed]