Category II (Indeterminate) FHR Tracing Classification
Marked baseline variability (option a) is the correct attribute that classifies a term pregnancy's continuous electronic FHR monitoring tracing as Category II: Indeterminate. 1
Understanding the NICHD Three-Category System
The National Institute of Child Health and Human Development (NICHD) classification system divides FHR tracings into three distinct categories, with Category II representing an indeterminate pattern that requires ongoing evaluation but does not mandate immediate delivery 1, 2.
Category I (Normal) Characteristics:
- Baseline FHR 110-160 bpm 1
- Moderate baseline variability (6-25 bpm) 1, 2
- Late or variable decelerations absent 1
- Accelerations present or absent 1
Category II (Indeterminate) Characteristics:
Marked baseline variability is specifically listed as a Category II finding 1. This category includes all FHR tracings not categorized as Category I or III and encompasses 1, 2:
- Baseline variability changes: absent (not accompanied by decelerations), minimal, or marked 1
- Baseline FHR changes: bradycardia (<110 bpm) without absent variability, or tachycardia (>160 bpm) 1
- Absence of FHR accelerations after fetal stimulation 1
- FHR decelerations without absent variability (variable or late) 1
Category III (Abnormal) Characteristics:
- Sinusoidal FHR pattern 1
- Absent baseline variability WITH recurrent decelerations (variable or late) and/or bradycardia 1, 2
Analysis of Each Answer Option
Option A: Marked Baseline Variability (CORRECT)
Marked variability is explicitly classified as Category II: Indeterminate 1. While moderate variability (6-25 bpm) is reassuring and defines Category I, marked variability (>25 bpm) represents an indeterminate pattern that requires continued monitoring and general measures 1, 2.
Option B: Accelerations Absent (INCORRECT for this question)
Accelerations can be present or absent in Category I tracings 1. However, absence of accelerations after fetal stimulation is a Category II finding 1. The mere absence of spontaneous accelerations alone does not automatically make a tracing Category II if other parameters are normal 1.
Option C: Sinusoidal Pattern (INCORRECT)
A sinusoidal FHR pattern is definitively classified as Category III: Abnormal, not Category II 1. This is a critical distinction, as sinusoidal patterns indicate severe fetal compromise requiring expedited delivery 1.
Option D: Early Decelerations Present (INCORRECT)
Early decelerations are benign findings that coincide with uterine contractions and represent fetal head compression 3. They are compatible with Category I (normal) tracings and do not elevate a tracing to Category II status 1.
Clinical Management Implications
When marked baseline variability or other Category II findings are identified 1, 2:
General measures include 1, 2:
- Vaginal examination to assess cervical status and rule out cord prolapse 1
- Maternal vital signs assessment (temperature, blood pressure, pulse) 1
- Oxygen administration at 6-10 L/min 1, 2
- Maternal position changes (left lateral) 1, 2
- Intravenous fluid administration or bolus 1, 2
- Discontinuation of oxytocin if being administered 1, 2
Consider expedited delivery if abnormalities persist or worsen 1, 2. Category II tracings may represent up to 80% of laboring patients at some point during labor 4, making proper identification and management essential.
Common Pitfalls to Avoid
Do not confuse marked variability with moderate variability 1. Moderate variability (6-25 bpm) is the hallmark of Category I and is highly reassuring, predicting absence of fetal acidemia 1, 2. Marked variability (>25 bpm) moves the tracing into the indeterminate Category II classification 1.
Do not mistake sinusoidal patterns for marked variability 1. Sinusoidal patterns have a smooth, sine wave-like appearance and are Category III, requiring immediate delivery 1.
Remember that isolated findings matter 5. Absence of variability combined with decelerations defines Category III, but marked variability alone (without absent variability and decelerations) is Category II 1, 5.