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:
Category II includes all FHR tracings not categorized as Category I or III and encompasses the following findings: 1
- Marked baseline variability (>25 bpm) 1
- Minimal baseline variability (absent variability NOT accompanied by decelerations) 1
- Baseline rate abnormalities: bradycardia (<110 bpm) not accompanied by absent variability, or tachycardia (>160 bpm) 1
- Absence of induced FHR accelerations after fetal stimulation 1
- Recurrent variable decelerations with minimal or moderate baseline variability 1
- Prolonged decelerations (>2 minutes but <10 minutes) 1
- Recurrent late decelerations with moderate baseline variability 1
Category III (Abnormal) Characteristics:
- Absent baseline variability WITH recurrent late or variable decelerations 1, 2
- Absent baseline variability WITH bradycardia 1, 2
- Sinusoidal pattern 1
Analysis of Each Answer Option
Option A: Marked Baseline Variability - CORRECT
Marked variability (>25 bpm) is explicitly listed as a Category II finding in the NICHD classification system 1. While moderate variability is reassuring and characteristic of Category I tracings, marked variability represents an indeterminate pattern that warrants continued monitoring 1, 2.
Option B: Accelerations Absent - INCORRECT as stated
The absence of accelerations alone does not automatically classify a tracing as Category II 1. Category I tracings can have accelerations "present or absent" 1. However, the absence of induced accelerations after fetal stimulation is a Category II finding 1. The question does not specify post-stimulation absence, making this option imprecise.
Option C: Sinusoidal Pattern - INCORRECT
A sinusoidal FHR pattern is explicitly classified as Category III (Abnormal), not Category II 1. This pattern indicates significant fetal compromise requiring expedited delivery 1, 2.
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 encountering marked baseline variability as part of a Category II tracing, implement the following approach 1, 2:
- Continue continuous electronic fetal monitoring with reassessment every 15-30 minutes 2
- Apply general measures: change maternal position, assess maternal vital signs, administer oxygen at 6-10 L/min, give IV fluids, and discontinue oxytocin if in use 1, 2
- Consider fetal scalp stimulation or acoustic stimulation to assess for fetal acidemia 1
- Consider expedited delivery if abnormalities persist or the pattern progresses to Category III 1, 2
Common Pitfall to Avoid
Do not confuse marked variability with moderate variability 1, 2. Moderate variability (6-25 bpm) is the hallmark of a reassuring Category I tracing and predicts absence of fetal acidemia 1, 2. Marked variability (>25 bpm) represents an indeterminate pattern that may indicate fetal stimulation or early compensation for stress, requiring closer observation 1.