What is the cardiotocographic record and what is it done for?

The cardiotocographic record may be slightly uncomfortable for the mother, but it provides valuable information about fetal well-being. We explain how this test is performed.

Last update: June 10, 2021

The cardiotocographic record, also called cardiotocography, it is a very useful tool in pregnancy. It is a test that allows to study the well-being of the fetus or the possible warning signs in it.

It consists of measuring the baby's heart rate, while monitoring the contractions in the mother's uterus. It can be applied both during childbirth and in the moments before it. It is essential in the mother's high blood pressure or gestational diabetes.

What is the cardiotocographic record?

The cardiotocographic registry is a study that allows to determine the well-being of the baby. The baby's heart rate is evaluated while the presence, frequency and strength of uterine contractions are studied. Thus, both parameters can be related.

Contractions are a movement that temporarily interrupts or reduces the passage of oxygen through the umbilical cord. Thus, the test gives indications of whether or not there is fetal well-being. In the same way, it serves to study if the fetus is ready for natural childbirth.

The problem is that the cardiotocographic record can be complex to interpret. In addition, it has some false positives (that is, results that are interpreted as pathological without being so). That is why it is accompanied by other methods, such as biophysical profile, ultrasound or Doppler flowmetry.

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When is it necessary?

The cardiotocographic record it is not usually recommended until after 32 weeks of gestation. The reason is that, due to its operation, it may be that if it is carried out before the results are not conclusive.

It is recommended in pregnant women with certain risk factors or when there is some alteration of the baby. For example, when the mother is less aware of fetal movements. The most frequent indications are hypertension and gestational diabetes. It is also done when the baby is small for the corresponding age.

In the same way, the cardiotocographic record can be useful in multiple pregnanciesas they carry more risk. The same is true if there is an alteration in the amount of amniotic fluid or labor begins earlier than expected.

Other common indications are the following:

  • Maternal fever or an ongoing infection.
  • Premature rupture of membranes.
  • The baby is in an unusual position. For example, in breech presentation.
Hypertension associated with pregnancy may require cardiotocography sometime near delivery.

Special Recommendations

The cardiotocographic record is usually carried out for 30 minutes. In addition, the duration of the test should be extended if a heart rate with a suspicious pattern is detected.

Sometimes several records are made throughout the day or continuous monitoring is used. There are times when registration is done on an outpatient basis.

In these cases, the reading can be carried out days later. So it is recommended to use other monitoring systems simultaneously, such as Doppler ultrasound. This way the results can be better compared.

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How is the cardiotocographic record done?

To perform the cardiotocographic recording, a specific device is required. It consists of two small transducers. One of them is in charge of monitoring uterine contractions and the other records the baby's heart rate.

Both transducers are placed on the mother's abdomen. The information obtained is simultaneously printed on a piece of paper, similar to that used in an electrocardiogram. The paper shifts 1 centimeter for every minute that passes.

Some inconvenients

The cardiotocographic recording can be uncomfortable for the mother. In fact, some women complain of back pain, because they have to hold the same position for so long.

According to a publication by the Badajoz Health Area, the registry also limits the mobility of women. This can be quite unpleasant during labor. For their part, false positives increase the rate of instrumented deliveries and cesarean sections.

There is no exact standardization of the patterns that the registry can display. That is why there are only recommendations regarding management, but there are not as specific criteria as in other practices.

How does the cardiotocographic registry work?

The cardiotocographic record has a relatively complex mechanism. According to a study carried out by the German Society of Gynecology and Obstetrics, a Doppler ultrasound is performed to obtain the fetal heart rate.

The ultrasound signals are transmitted by a transducer in the mother's abdomen. These signals are reflected from the baby's heart. Thus they return to the transducer and the device uses algorithms to calculate the frequency. What it does is rebuild the frequency from that algorithm.

On the other hand, the recording of contractions is carried out thanks to a transducer that measures abdominal pressure. This converts the tension produced by the contractions into a written signal. This is how the frequency and duration information is obtained.

Contractions have frequency and duration. The first thing is how many times they repeat in a minute. The second is how long the uterus remains contracted each time.

Results analysis

Interpreting a cardiotocographic record can be complex. The usual thing is that the fetal heart rate ranges from 120 to 160 beats per minute. However, the lower the gestational age, the higher this value.

The recording is considered normal or reactive if during the study the baby's heart races at least twice in 15 seconds. Similarly, accelerations must be more than fifteen beats above the baseline. Thus it is considered suggestive of fetal well-being.

The result of the cardiotocographic recording may be abnormal or non-reactive as well. In this case, what happens is that the baby's heart rate does not accelerate with movement or with contractions.

A test that is complemented by others

The cardiotocographic record is an examination that allows to evaluate the fetal well-being. It is used to measure the baby's heart rate, while uterine contractions are monitored. This is how it is checked whether the heart responds adequately to movements.

This exam is not done routinely. It is indicated when there is a maternal pathology that can put the baby at risk. Also when an anomaly has been detected.

It is a non-invasive test, but that is somewhat annoying for the mother, especially during childbirth. Additionally, you have the ability to report false positives. Therefore, it is recommended to supplement with other relevant parameters.

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