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 Fetal heart rate monitoring was introduced to allow clinicians to identify fetuses experiencing hypoxia or asphyxia and ‘‘rescuing’’ them with immediate delivery, often via cesarean. Cardiotocography (CTG), a screening test for fetal hypoxia during labor, is a continuous graphic record of fetal heart rate (FHR) and uterine contractions. During the second stage of labor, if the abdominal transducer is moved downward to improve the signal quality of the CTG trace, the transducer can pick up sound waves reflected by movements of maternal vessels. This results in recording of maternal heart rate (MHR), which may mimic the FHR and lead to an adverse outcome because the fetus is not monitored during the time of hypoxic stress. Cardiotocography relies on pattern recognition; therefore, clinicians must have a thorough understanding of the features of MHR that differentiate it from FHR during labor. An external ultrasound transducer is one method for recording the FHR, but if it is not placed over the fetal heart, it can record the MHR. Internal recording of the FHR using a scalp electrode is a more accurate method. Fetal electrocardiogram waveforms are obtained by attaching a fetal scalp electrode as well as another reference electrode on the mother’s thigh. A typical CTG records uterine contractions and the baseline rate, baseline variability, accelerations, and decelerations of the FHR. During uterine contractions, the FHR shows decelerations, but the MHR shows accelerations, reflecting a transient contraction related to increased cardiac output FHR accelerations are more common with external FHR monitoring than internal monitoring using a scalp electrode. Clinicians should consider the possibility of erroneous recording of MHR if accelerations coincide with uterine contractions during the second stage of labor. The likelihood of observing accelerations coinciding with uterine contractions is less than 50% using internal FHR monitoring compared with external monitoring. Absence of p-wave on the electrocardiogram waveform or simultaneous use of maternal pulse oximetry to record MHR may help clinicians exclude MHR monitoring Since its advent in the 1970s, there is minimal or no impact on the incidence of hypoxic ischemic encephalopathy or cerebral palsy, whereas the rate of cesarean delivery has risen from 5% to 33%. Given this finding, it might seem like fetalheart monitoring has nothing to offer those providers who take care of women on labor and delivery. However, there has been a reduction in the rate of intrapartum stillbirth. My interpretation of CTG monitoring is that,some foetuses who would have ended up stillborn are now delivered with hypoxic ischemic encephalopathy. Alternatively, some who would have had hypoxic-ischemic encephalopathy (HIE) are now born without injury. Although there are no population studies that demonstrate the above argument, certainly, we have all performed operative deliveries in the setting of abruption, cord prolapse, or uterine rupture that resulted in a noninjured baby, and we were warned of the event because of a fetal bradycardia or repetitive FHR decelerations. Another reason why FHR monitoring has not lived up to its expectations and has led to a great deal of harm is lack of good studies that have determined what FHR characteristics and patterns are predictive of fetal harm or well-being. What are the problems of foetal monitoring in second stage? The common issue is simply a failure to closely monitor the fetus, particularly in the second stage. During maternal expulsive efforts, there is often dropout of the FHR when monitored externally. Furthermore, as the fetus moves down the birth canal, not infrequently, it is the MHR that is monitored, rather than fetal. Furthermore, because the MHR often rises in the second stage due to the patient’s physical exertion, it may be in the normal baseline range for an FHR. This confusion can lead to the delivery of a hypoxic, academic neonate for whom the providers are not prepared because they anticipated a normal outcome based on the heart rate monitoring that was performed. With internal monitoring, fetal heart accelerations with contractions are rare, occurring upto 4% of the time. However, with the external monitoring, it is 12%. This would suggest that perhaps as much as 8% of fetal monitoring performed by external monitoring in the second stage was actually recording the MHR.  If there is any doubt about FHR vs MHR, then one should start, Monitoring the woman  with a pulse oximeter in the second stage, and if there is any question about similarity between the maternal and FHR, a scalp electrode is placed. A caveat that is important to note is that a fetal scalp electrode placed on a fetal demise can continue to pick up the MHR. This is a rare, but sobering reminder to pay close attention to both the fetal and MHRs throughout labor, and particularly during the second stage when the MHR can rise because of the physical exertion. When you see FHR accelerations during contractions, be particularly suspicious and ensure you are monitoring the baby, not the mother. (Ref: Obs and Gynae Survey Apr.2013)