North American Registry of Midwives (NARM) Practice Exam

What describes a sinusoidal pattern of fetal heart tones (FHT)?

1. Irregular spikes and dips

2. Undulating, repetitive pattern

3. Flat baseline with variations

4. Non-repetitive gradual changes

The correct answer is: Undulating, repetitive pattern

A sinusoidal pattern of fetal heart tones is characterized by an undulating, repetitive pattern. This is a specific type of fetal heart rate variability that is smooth and has a regular amplitude and frequency. It suggests a particular physiological state of the fetus, often associated with certain conditions such as fetal anemia or other forms of compromise that may be impacting the fetal environment. The undulating nature means that the heart rate swings in a smooth, wave-like manner rather than exhibiting jagged spikes or irregular patterns. A flat baseline with variations doesn't fit this description as it lacks the consistent wave-like appearance. Similarly, irregular spikes and dips present a more chaotic and non-repetitive pattern, which does not represent the regular oscillation found in sinusoidal patterns. Non-repetitive gradual changes indicate variability but do not capture the essential rhythmic quality of the sinusoidal pattern. Thus, the repetitive and undulating nature is what correctly identifies a sinusoidal fetal heart tone pattern.