In cardiotocography (CTG), a sinusoidal fetal heart rate pattern is most indicative of which condition?

NORCET 10 Prelims-2026

Obstetrics & Gynaecology

Easy

Appeared in: NORCET 10 Prelims-2026

Explanation

A sinusoidal pattern is a smooth, regular, sine-wave-like tracing of the fetal heart rate (FHR).
It is a rare but ominous (non-reassuring) pattern that signifies severe fetal compromise.
This pattern is strongly associated with conditions causing profound fetal hypoxia and acidosis, such as severe fetal anemia, which fall under the general category of fetal distress.
Key features include absent beat-to-beat variability, an amplitude of 5-15 bpm, and a frequency of 2-5 cycles per minute, lasting for at least 20 minutes.

Option B: A true sinusoidal pattern is a pathological sign indicating a high risk of fetal morbidity and mortality; it is never considered a normal or reassuring finding.
Option C: This describes fetal tachycardia, which is a baseline FHR above 160 bpm. While tachycardia can be a sign of fetal distress, it is a different FHR pattern from the characteristic undulating wave of a sinusoidal trace.
Option D: Maternal hypertension typically causes uteroplacental insufficiency, which classically presents as late decelerations on a CTG, not a sinusoidal pattern.

Visual 1: CTG Tracing - An image displaying a classic sinusoidal fetal heart rate pattern, highlighting its smooth, wave-like appearance and lack of variability.
Visual 2: Infographic - A comparative chart showing the differences in appearance and clinical significance between a true sinusoidal pattern, a pseudosinusoidal pattern, and a normal reactive FHR pattern.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Interpretation of Cardiotocography (CTG) patterns, specifically the sinusoidal fetal heart rate (FHR) pattern as background academic context rather than a clinical decision trigger.
The ability to recognize a sinusoidal pattern is a critical nursing skill, as it signals a fetal emergency requiring immediate intervention.
Upon identifying a sinusoidal pattern, the nurse's priority is to notify the obstetrician or senior midwife immediately and prepare for urgent, often emergency, delivery.
It is essential for the nurse to consider the clinical context, such as recent administration of narcotic analgesics (e.g., pethidine), to differentiate between a true and a pseudosinusoidal pattern.

How to Approach the Question

First, identify the key term in the question: 'sinusoidal fetal heart rate pattern'.
Recall the classifications of fetal heart rate (FHR) patterns into reassuring, non-reassuring, and ominous categories.
Remember that the sinusoidal pattern is a specific, non-reassuring (ominous) pattern with a distinct sine-wave appearance and absent variability.
Associate this pattern with its primary clinical significance, which is severe fetal compromise (hypoxia, anemia, acidosis).
Evaluate the options. 'Fetal distress' is the broad clinical term that encompasses the severe conditions indicated by a sinusoidal pattern.
Eliminate the other options by recalling their definitions: a 'normal finding' is reassuring, 'increased fetal heart rate' is tachycardia, and 'maternal hypertension' typically causes late decelerations.

Concept Tested & Keywords

Concept Tested: Interpretation of Cardiotocography (CTG) patterns, specifically the sinusoidal fetal heart rate (FHR) pattern.
Stem keywords: Cardiotocography, CTG, sinusoidal fetal heart rate pattern
Lead-in keywords: most indicative of
Negative lead-in flag: false

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