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CTGs monitor the unborn baby's heartbeat and how this is behaving. The contractions are also monitored and their frequency, timing and duration are recorded. Standard CTGs do not measure the strength of contractions.

 

By looking at the pattern of the heartbeat, both in isolation and in relation to the uterine contractions, it is possible for a midwife or doctor to identify features suggestive of fetal distress.

 

 

Continuous CTG monitoring throughout labor

Different obstetric units operate different policies on this matter. However, the scientific evidence available indicates that properly timed intermittent monitoring is just as good as continuous monitoring in its ability to detect fetal distress. This applies to low-risk pregnancies, which are the majority.

 

For high-risk pregnancies, such as in cases of intrauterine fetal growth restriction (IUGR) or previous unexplained stillbirth, there is consensus that continuous monitoring is the appropriate policy. This is because the behaviour of such babies is less predictable and this measure will be reassuring to the parents, who will be inevitably anxious.

 

The diagnostic value of CTG

The CTG is not diagnostic. All it does is point towards the probability of fetal distress.

 

A normal CTG is always reassuring whilst a suspicious or frankly abnormal CTG is not always significant. In fact, the majority of CTGs classified as unsatisfactory or suspicious will turn out to be false scares, with babies being born perfectly healthy with no hint of distress.

 

It is an accepted fact that this technology, whilst extremely valuable, is nonetheless, a significant cause of over-intervention in labor. Nobody doubts that the CTG has single-­handedly increased the rate of cesarean section quite substantially. However, one needs to acknowledge that this technology has also saved the lives of millions of babies. The increased rate of intervention is probably a small price to pay for the greater good.

 

Verifying the findings of a suspicious CTG

Once a suspicious CTG trace is identified, the standard next step is to obtain a small sample of blood from the baby to have it analyzed for oxygen saturation. This is much more definitive.

 

The blood is obtained by scratching the leading part of the baby (usually the scalp). A drop of blood is collected in a fine capillary tube and put in a machine which gives results in about a minute. In the majority of cases, the results are reassuring but in some, the results will confirm the fetal distress suspected earlier, therefore calling for expedited or immediate delivery.

 

When the blood analysis confirms fetal distress, the action taken will depend on the degree of abnormality. If the reflected distress is only mild, action such as changing the position of the mother, stopping or reducing the rate of oxytocin infusion and giving oxygen to the mother may be all that is required. With that, improvement on the CTG may soon be apparent and, if need be, a repeat sample is taken after some time to reassure everybody concerned.

 

If there is significant distress, then delivery by the quickest means possible will be carried out. This may be a cesarean section but it may also be by forceps or ventouse vaginal delivery, if this is feasible.

 

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