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Calibration of the CTG

Calibration of the CTG. Calibration of the CTG. Calibration of the CTG. Calibration of the CTG. Features and Terminology of CTG. The four main features of CTG are: Baseline rate. Baseline variability. Accelerations. Decelerations. Baseline Fetal Heart Rate.

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Calibration of the CTG

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  1. Calibration of the CTG

  2. Calibration of the CTG

  3. Calibration of the CTG

  4. Calibration of the CTG

  5. Features and Terminology of CTG • The four main features of CTG are: • Baseline rate. • Baseline variability. • Accelerations. • Decelerations.

  6. Baseline Fetal Heart Rate • Baseline rate is defined as the level of the fetal heart rate when it is stable, excluding accelerations and decelerations. • It is determined over a time of 5-10 minutes, and expressed in beats per minute.

  7. Normal Baseline FHR

  8. Baseline Bradycardia

  9. Baseline Tachycardia

  10. Baseline Variability • Baseline variability is the minor fluctuations in baseline fetal heart rate occurring over 3-5 cycles/minute.

  11. Normal Variability

  12. Reduced Variability

  13. Reduced Variability

  14. Accelerations • Accelerations are abrupt, transient increase in fetal heart rate of  15 bpm, lasting for  15 seconds. • The absence of accelerations with an otherwise normal CTG is of uncertain significance.

  15. Acceleration

  16. Decelerations • Decelerations are a transient slowing of the fetal heart rate below the baseline of  15 bpm for  15 seconds. • There are 5 types of decelerations: • Early deceleration • Late deceleration • Variable deceleration • Atypical variable deceleration • Prolonged deceleration • In addition, there are one specific pattern: • Sinusoidal pattern

  17. Early Decelerations • Uniform, repetitive, periodic slowing of the FHR with onset early in the contraction and return to baseline at the end of contraction. • The lowest point of the deceleration coincides with the highest point of the contraction wave. • Usually associated with head compression. • Tend to occur late in the first stage or during the second stage of labor. • Benign, not significant, not associated with fetal hypoxia.

  18. Early Decelerations

  19. Early Decelerations

  20. Early Decelerations

  21. Late Decelerations • Uniform, repetitive, periodic slowing of the FHR with onset mid- to the end of the contraction. • The lowest point of the deceleration more than 20 seconds after the peak of the contraction wave, always ending after the contraction. • In non-accelerative trace, with baseline variability < 5 bpm, the definition would include decelerations < 15 bpm. • Late decelerations, if present for > 30 minutes, are always indicative of fetal hypoxia, and further action is indicated.

  22. Late Decelerations

  23. Late Decelerations

  24. Late Decelerations

  25. Variable Decelerations • The MOST COMMON form of decelerations occurring during labor. • Variable, intermittent, periodic slowing of the FHR, with rapid onset and recovery. • Time relationships with contraction waves are variable. Sometimes, they may resemble other types of decelerations in timing and shape.

  26. Variable Decelerations – cont’d • Variable decelerations are often caused by umbilical cord compression. • Variable decelerations are either typical or atypical. • Typical variable decelerations are an autonomic nervous system response to cord compression and are indicative of the fetus coping well.

  27. Variable Decelerations – cont’d • However, the fetus may become tired over time and, if typical variable decelerations occur with over 50% of contractions for more than 90 minutes, this should be regarded as non-reassuring, particularly if there is any degree of fetal compromise such as fetal growth restriction. • Atypical variable decelerations may subsequently develop indicating that the fetus is now less able to cope with cord compression.

  28. Pure (Typical) Variable Decelerations

  29. Prolonged Decelerations • An abrupt decrease in FHR to levels below the baseline that lasts at least 60-90 seconds. • If fetal bradycardia occurs for more than 3 minutes, plan should be made to urgently expedite delivery. A “category 1” birth should be declared and the woman should be immediately transferred to the theatre. If the fetal heart rate recovers within 9 minutes, the decision for immediate delivery should be reconsidered, if reasonable, and in consultation with the woman.

  30. Prolonged Decelerations

  31. Sinusoidal Pattern • A regular oscillation of the baseline long-term variability (resembling a sine wave). • Smooth, undulating pattern, lasting at least 10 minutes, has a relatively fixed period of 3-5 cycles per minute at an amplitude of 5-15 beats per minute above and below the baseline. • Baseline variability is absent. • A true sinusoidal pattern is an abnormal feature and is associated with high rates of fetal morbidity and mortality.

  32. Sinusoidal Pattern

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