Fetus

Fetal Heart Tone Sinusoidal Pattern

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Fetal Heart Tone Sinusoidal Pattern, FHT Sinusoidal Pattern, FHR Sinusoidal Pattern, FHR Pseudo-sinusoidal Pattern

  • Definition
  1. Smooth undulating sine wave pattern
  2. Amplitude: 10 to 15 bpm
  3. Frequency: 3-5 cycles per minute
  4. Duration: >2 minutes
  • 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
  • Differential Diagnosis
  1. Pseudo-sinusoidal FHR pattern
    1. Appears similar to sinusoidal pattern
    2. Short-term variability present
    3. Benign finding
  • 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]