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ESSAY 166 - CTG

Posted by Nitin P.
Cardiotocography is the graphical representation of fetal heart rate over a period of time and it is used for monitoring apparent fetal well being. The use of CTG in labour was started before trials could show any definite reduction in neonatal morbidity or mortality in low risk cases.
It is difficult to define low risk cases, especially since a number of suboptimal outcomes occur in such pregnancies.
However, there is no evidence to perform an admission CTG to help identify the low and high risk cases.
There is also poor correlation between an abnormal CTG, Apgar scores, Hypoxia and long term neonatal outcome. Including development at age of 5 years. There is no good evidence that performing CTG in all low risk cases, will lead to further reduction in the incidence of neonatal morbidity and cerebral palsy.
There is also evidence regards no difference in outcome when CTG is compared to intermittent auscultation in low risk cases.
Interpretation of CTG is subjective, until computerised CTG interpretation gets validated. The CTG also has a high sensitivity but low specificity. This leads to an increased number of interventions. Where fetal blood sampling is available, the number of procedures is increased due to presumed fetal compromise.
Where FBS is unavailable, unacceptable to the mother, or not possible due to technical reasons, CTGs lead to an increase in the caesarean section rate.
Training of staff and medical students in CTG interpretation is therefore important.
Maternal mobility is also limited due to continuous CTG, leading to poor perception of labour. Also many mothers resent the medicalisation of labour.
The cost of equipment, maintenance is increased when used for all cases.
Staff training and revalidation of training is important for the correct interpretation of the CTG. To monitor all the low risk cases, a higher number of trained staff would be needed.
The CTG has a definite role if any high risk factor develops in labour such as meconium stained liquour, FHR >160 on intermittent auscultation or use of oxytocin or epidural analgesia. Also a reassuring CTG in low risk cases with less than optimal outcome will help to reduce the cost of litigations.
Thus, in the present situation, the CTG is not recommended in all low risk cases, as the benefits donot outweigh the risks.
Posted by Rani M.
Labour poses specific risks to the baby such as hypoxia/acidosis, abruptio placentae and cord prolapse. Aim of fetal monitoring during labour is to detect these adverse events so that timely action can be taken to prevent or minimise perinatal morbidity & mortality.Commonly used methods for fetal monitoring are intermittent auscultation of fetal heart or continous electronic fetal monitoring ( C.T.G.)

CTG has good sensitivity to detect fetal hypoxia /acidosis at that particular time but has low specificity and can not predict events such as abruption and cord prolapse.
However there is some evidence that CTG is associated with lower incidence of neonatal seizures though these seizures were not the one associated with cerebral palsy.
CTG can detect variable decelerations and can differentiate between early , variable and late decelerations which is not possible with intermittent auscultation. If interpreted by an experienced senior obstetrician CTG is a useful technique. It is reassuring for the mother to see a normal trace ongoing.Similarly in accordance with risk management and for archival purposes CTG records can be kept for many years after the delivery. NICE recommends storing CTG traces for upto 25 years. This is useful in case of future litigation. Moreover no labour can be safely guranteed as low risk from the start, things may go wrong and problems may be detected such as meconium staining or blood mixed liquor which reclassify the labour as high risk.

There is no evidence that CTG is associated with a better perinatal outcome as compared to intermittent auscultation in low risk uncomplicated labours.
Infact its use on its own has been associated with increase in the incidence of cesarean sections.Though this increase was not seen if abnormal CTG was supplemented with fetal blood sampling. There is a poor correlation between abnormal CTG and umblical artery pH.Henceforth fetal acidosis need to be confirmed by fetal blood sampling which is an invasive procedure, uncomfortable for mother and can not be undertaken in presence of coagulopathies or maternal infections such as HIV.

Interpretation of CTG is another limitation which requires adequate training, education and experience.Computerized analysis may be useful. Regular training of all staff involved in CTG is required.
It is expensive, requires expensive equipment and CTG papers.Some woman may resent it as medicalisation of labour especially in low risk cases which may be looked forward as a natural birth process. It restricts the mobility of woman.To some degree there is risk of generating complacency and tendency to leave woman alone for long periods by caring staff.

Intermittent auscultation need to be done every 15 to 30 minutes during first stage, 30-45 seconds out of which should be after contraction; during second stage need to auscultate every 5 minutes or after each contraction.This can detect only late decelerations and no idea regarding variability and variable decelerations can be made out. But in low risk cases it has been found to be as effective as CTG in terms of perinatal outcome.It is cheap, simple and does not restrict women\'s mobility. But the process is tedious and requires considerable input from staff.Moreover may need to switch over to CTG monitoring if there are abnormalities detected by intermittent auscultation.

IN conclusion the decision can only be taken after thorough informed counselling of the woman regarding available data, evidence, limitations and benefits of both methods. Her decision should be respected and dicussion need to be documented in the notes.While in low risk uncomplicated labours current evidence does not favour routine use of CTG; in high risk labour its benefits far outweigh the risks.
Posted by manjula C.
Low risk uncomplicated labour is defined as labour of spontaneous onset at term with an uncomplicated antenatal period and no risk factors for fetal compromise (like IUGR, PE etc). Cardiotocograpy (CTG) is a graphic record of fetal heart rate (FHR) plotted simultaneously with a record of uterine activity. Monitoring of fetal activity in this way assumes that uterine activity during labour is a significant interference in fetal O2 supply is recognizable.

Aim of CTG monitoring in labour is to detect fetal compromise before irreparable damage, to prevent fetal demise and long term consequences such as cerebral palsy with sufficient sensitivity, specificity and timeliness to allow intervention.

There is evidence that CTG monitoring reduces perinatal mortality in terms of neonatal encephalopathy and seizures (50%). It is reassuring for some labouring mothers. Printed CTG records helps in risk management.

CTG monitoring has many disadvantages. CTGs have low specificity; large number of uncompromised fetus would have a non-reassuring CTGs, resulting in increased intervention rates in the form of fetal blood sampling(FBS), operative vaginal delivary and Caesarean section(CS) with no significant difference in long term neonatal outcome. FBS if unavailable, unacceptable to the mother & technically difficulties, results in further increase in intervention rates. There is a poor correlation between CTG abnormality and short term outcomes such as Apgar scores at 1min. and 5 min. and neonatal admission rates. CTG do not predict conditions like abruptio placeta and cord prolapse, may however contribute to a definitive diagnosis. CTG interpretation is subjective and is liable for inter and intra observer variations. Maternal mobility is restricted; some women may resent invasive monitoring. Cost of equipment, its maintenance and staff training all have financial implications.

There is no evidence that CTG monitoring of all women in labour will lead to reduction in neonatal morbidity and cerebral palsy. Incidence of cerebral palsy is around 1-2/1000 and has not been changed over the last 30 years despite the extensive use of CTG and other newer modalities of fetal monitoring. There is no difference in fetal outcome in CTG monitoring and intermittent auscultation in low risk labouring mothers. CTG monitoring in low risk cases does more harm than good, hence the current consensus is that CTG monitoring should be restricted to high risk cases. Intermittent auscultation with portable Doppler FHR detector is adequate and equally effective for low risk cases to avoid unnecessary interventions, operative virginal delivary, Caesarean section and consequent maternal & fetal morbidity.
Posted by Mangala sundari R.
External or internal cardiotcograph(CTG) monitoring is done to trace the fetal heart in the antenatal surveillance and in labour to asses the fetal well being.

CTG in low risk uncomplicated labour has increased the intervention rate like instrumental delivery and C.section with its associated morbidity.The interpretation of the various findings like, type 1, variable or delayed decelarations need to be done accurately in the clinical situations.This has inter observer errors and needs training.But at the same time the findings of CTG should be substantiated with fetal blood sampling before the decision is taken to deliver the baby immediately.This facility or the training may not be available in all centres.More over there is poor correlation between CTG, apgar scores at 5 minutes and the outcome .
10 to 15 % of cerebral palsy are due to intrapartum events . CTG cannot predict or diagnose such events like cord prolapse or abruptio placenta.But fetal heart tracing will be of value in these conditions.
some women donot like the idea of invasive monitoring in the baby.women cannot be mobile in labour and may feel distressed about it. And some women may feel reassured with the monitoring that everything is going on well.
CTG monitoring in labour is associated with fewer admissions to SCBU, lesser number of neonates to receive 21% oxygen ,reduction in the number of neonatal seizures ,but these are not the ones associated with long term morbidity.

patients are counselled about the advantages and disadvantages of the CTG before the decision for type of monitoring is undertaken.
In this era of medical litigation ,from the medicolegal point of view, CTG stands proof to justify the course of events, the timing and the interventions taken by the obstetrician.