II. Definition

  1. Smooth undulating sine wave pattern
  2. Amplitude: 10 to 15 bpm
  3. Frequency: 3-5 cycles per minute
  4. Duration: >2 minutes

III. Causes

  1. Ominous sign
    1. May represent terminal rhythm
    2. Requires immediate evaluation
  2. Severe fetal Anemia (e.g. Fetal hydrops)
  3. Maternal medications or Illicit Drugs

IV. Differential Diagnosis

  1. Pseudo-sinusoidal FHR pattern
    1. Appears similar to sinusoidal pattern
    2. Short-term variability present
    3. Benign finding

V. References

  1. Bailey (2000) ALSO, E:1-13
  2. Gabbe (2002) Obstetrics, p. 395
  3. Rylander (2001) Clin Fam Pract 3(2):287-305 [PubMed]

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