Cardiotocography

• When Cardiotocography (CTG)  is normal there is a predictive value of 99% for confirming a non-acidic foetus, and an abnormal CTG  tracing has a positive predictive value of 50% for foetal compromise.[
  The following popper user interface control may not be accessible. Tab to the next button to revert the control to an accessible version.
  Destroy user interface control6] Measurement of intrapartum acid base status obtained from foetal scalp blood helps to decrease operative deliveries following false positive foetal heart tracings.[
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• Sinusoidal trace : It indicates Fetal anemia and hypoxia. You will never see accelerations in a sinusoidal CTG trace. Ecah sinusoidal wave is a mirror image of previous one.The true sinusoidal pattern is rare but ominous and is associated with high rates of fetal morbidity and mortality
• It is a regular, smooth, undulating form typical of a sine wave that occurs with a frequency of two to five cycles per minute and an amplitude range of five to 15 bpm. It is also characterized by a stable baseline heart rate of 120 to 160 bpm and absent beat-to-beat variability. It indicates severe fetal anemia, as occurs in cases of Rh disease or severe hypoxia

• Pseudosinusoidal trace : The amplitude varies and becomes normal after 30-40 minutes. A pseudosinusoidal pattern shows less regularity in the shape and amplitude of the variability waves and the presence of beat-to-beat variability, compared with the true sinusoidal pattern

• Saltatory trace : The saltatory fetal heart rate pattern is defined as fetal heart variability of > 25 beats per minute with an oscillatory frequency of >6 per minute for a minimum of one minute. This indicates something very acute such as occult cord prolapse, uterine rupture or concealed abuption. In the absence of abnormal periodic fetal heart rate changes and with the presence of short-term and long-term variability, the saltatory fetal heart rate pattern appears benign.

          Increased variability in the baseline FHR is present when the oscillations exceed 25 bpm . This pattern is sometimes called a saltatory pattern and is usually caused by acute hypoxia or mechanical compression of the umbilical cord. This pattern is most often seen during the second stage of labor. The presence of a saltatory pattern, especially when paired with decelerations, should warn the physician to look for and try to correct possible causes of acute hypoxia and to be alert for signs that the hypoxia is progressing to acidosis.21

Ominous pattern CTGs

Persistent late decelerations with loss of beat-to-beat variability at the trough

Nonreassuring variable decelerations associated with loss of beat-to-beat variability

Prolonged severe bradycardia lasting more than 6 minutes with no signs of recovery

Sinusoidal pattern When to consider Fetal blood sampling? A growing body of evidence suggests that, when properly interpreted, FHR assessment may be equal or superior to measurement of fetal blood pH in the prediction of both good and bad fetal outcomes.13Fetuses with a normal pH, i.e., greater than 7.25, respond with an acceleration of the fetal heart rate following fetal scalp stimulation. Fetal scalp sampling for pH is recommended if there is no acceleration with scalp stimulation.11 Emergency Interventions for abnormal CTG patterns Call for assistance Administer oxygen through a tight-fitting face mask Change maternal position (lateral or knee-chest) Administer fluid bolus (Hartman's / Normal saline) Perform a vaginal examination and fetal scalp stimulation Consider tocolysis (for uterine tetany or hyperstimulation) Discontinue oxytocin if used When possible, determine and correct the cause of the pattern (such as abruption, uterine rupture, occult cord prolapse, chorioamnionitis) Determine whether operative intervention is warranted and, if so, how urgently it is needed Causes of Severe Fetal Bradycardia Prolonged cord compression Cord prolapse Tetanic uterine contractions Epidural and spinal anesthesia Rapid descent Vigorous vaginal examination