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Pregnancy Bliss | Reproductive Health Hub

Labour onset Head engagement ECV video Latent Phase Stages of labour Labour progress Pushing Episiotomy Afterbirth (Placenta) Fetal monitoring

Fetal Monitoring in labour

How effective are the fetal monitoring methods in labour?

Pretty effective but they are not infallible. It is, however, extremely unusual to be unable to detect a baby in trouble. The one charge against the current monitoring methods that will stick is the fact that, as a result of them, there is over-­intervention.

How is a baby monitored in the uterus?

In the Western world, the standard is electronic fetal monitoring. It is what is known as a "cardiotocograph" or CTG.

A CTG continually monitors the activity of the fetal heart (hence cardio-) and also monitors the contractions (toco-).

On looking at a trace made by the machine, a trained person will be able to distinguish a normal from an abnormal pattern.

How does CTG monitoring cause over-intervention?

A CTG is excellent in telling a normal pattern. This means, when it indCTG monitoringicates that things are normal, they almost certainly are.

Unfortunately, an abnormal pattern cannot be taken at face value. Its positive predictive value is rather poor. Some experts quote a figure of 30%

This means, about 70% of the seemingly abnormal traces will be from babies that are perfectly happy. A doctor, therefore, has a duty to analyze each apparently abnormal pattern and take the appropriate steps.

Fetal Blood Sampling (FBS)

So what kind of intervention is available if the CTG trace raises suspicions?

The doctors need to make a critical assessment of the situation. If the pattern is benign enough and there is no other evidence of possible fetal distress, then waiting and watching for developments is the logical option.

If the pattern is causing sufficient concern, then there is a way of objectively verifying the situation. This is by taking a tiny sample of blood from the fetus and having it analyzed by a special machine to check the acid-base balance and oxygenation of the baby's blood.

If the pattern looks alarming and if there is little doubt that the baby needs bailing out, then it is up to the doctor to move fast and deliver the baby by the quickest means feasible. This could be by instrumental delivery (such as forceps or ventouse) or by caesarean section.

How is a blood sample obtained from an unborn baby?

As mentioned above, a fetal blood sample may be required to verify whether an abnormal CTG truly reflects a fetus in trouble.

This is obtained by making a tiny scratch on the fetal scalp (or the buttock, if the baby is breech-presenting). A sample is made up of about two small drops of blood. Usually, two samples will be taken, to ensure a correct reading has been obtained. The whole procedure takes 3 - 5 minutes from beginning to end, and the results are available within two minutes of taking a sample.

It is a truly remarkable piece of technology which has saved millions of mothers from an unnecessary caesarean section. In addition - and probably more importantly - it has allowed timely intervention where this is required. This is because the results do not only show where there is distress, they also show the actual degree of distress and therefore guide the speed of intervention, if required.

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