The norm of CTG values during pregnancy

Fetal cardiotocography is a study that is carried out for all pregnant women after 28-29 weeks. Most often, diagnosis is sent at 32-34 weeks, if there are no complications. What allows you to see CTG and what are the norms of values, we will tell in this article.

Method essence

CTG is considered one of the most informative diagnostic methods in the third trimester of pregnancy.

The tiny heart works in full accordance with the general condition of the child. If the baby is healthy and well, then the heart beats rhythmically and clearly. The small heart reacts to any disorders, diseases, pathological conditions by increasing or decreasing the rhythm.

Cardiotocography is performed two to three times at a later date, usually after 30 weeks, and then before delivery at 38-40 weeks. If the pregnancy is not going well, the doctor may recommend additional CTGs.

Cardiotocography is done to find out how the baby is feeling.

During childbirth, the device is also connected to the belly of the pregnant woman in order to monitor the well-being of the baby while she goes through the difficult, but nature-provided path.

With the help of two sensors, measurement of several indicators at the same time, which are considered together. This is the nature and frequency of the beating of a child's heart, contraction of the uterine muscles and fetal movement.

One of the sensors is a conventional ultrasonic recorder. Its task is to record the heartbeat of the child.

Another sensor is called a strain gauge, it is a wide Velcro belt that surrounds a woman. Its task is to register uterine contractions (or labor pains, if the method is used during childbirth) based on minor fluctuations in the volume of the abdomen. The same sensor "captures" the movement of the fetus inside the uterus.

The indicators are recorded simultaneously, synchronously in two graphs. On one - data on the heartbeat of the child, on the second - uterine contractions and movements. The readings of the upper graph on the time scale completely correspond to the lower one, therefore all parameters are interconnected with each other.

The survey lasts from 30 minutes to 1 hour, sometimes the procedure for registering indicators can be extended. Undergo CTG in consultation at the place of residence, as well as in any clinic that provides pregnancy management services.

Decoding and norms

With the advent of modern fetal monitors, the problem of decoding difficult terms used in CTG has become an easier task, because the apparatus itself analyzes the data obtained and issues a conclusion. In it, a woman always sees the main thing - the cherished record “the fetus is healthy”. But such a record does not always appear, alas.

In addition, expectant mothers really want to know as much as possible about their son or daughter. We will try to explain what the entries in the conclusion of cardiotocography mean and what the norms are.

Basal heart rate

Everyone knows that the heart of a child who has not yet been born beats often - more than 110 beats per minute. But a woman who first came to CTG is waiting for another discovery - a small heart not only beats quickly, it beats at a different pace.

The speed changes almost every second - 145, 150, 132 and so on. It would be difficult to determine the norm for a particular child if it had not been derived mean - the so-called basal heart rate.

During the first minutes, the program analyzes all incoming values, and then determines the arithmetic mean. The normal basal heart rate is considered to be values from 110 to 160 beats per minute. An excess may indicate tachycardia, a heart rate below 110 beats per minute may indicate bradycardia. Both the increase and decrease in the same degree can be physiological, and can indicate a child's trouble.

Many women mistakenly think that the heart rate of the baby changes by week, and therefore they are looking for compliance with the norm at 33, 36 or 35 weeks of pregnancy. The rates are the same for the entire third trimester. They do not depend on a specific period, and also cannot indicate the gender of the child.

Variability, heart rate range

As soon as the baseline value of the heart rate is displayed, the program begins to record the variability or heart rate range. Under this concept, rhythm fluctuations are hidden up or down from the average value.

The readings can change quickly or slowly. Therefore, the oscillations themselves (or, as they are also called in the medical environment, oscillations) are also slow and fast.

Fast vibrations are practically a change in rhythm every second. There are three types of slow oscillations:

Low - when the baby's heart changed the rhythm rate for a minute of real time by no more than three beats. Low sequences look like this: 145, 146, 147, 144, and so on. This is called low variability.
Medium oscillations are characterized by a change in the heart rate by 3-6 beats per minute, and high oscillations - more than six. Thus, fluctuations from a baseline value of 140 beats per minute in 60 seconds to values of 145 are average variability, and up to 152 values, a high variability. The norm during pregnancy is fast and high oscillations.
In addition, the quantitative indicator of oscillations is assessed. A fetal heart rate is considered monotonous if the heart rate changes by no more than 5 beats per minute. A transitional rhythm is called a rhythm in which a change occurs by 6-10 beats per minute. The wavy rhythm is characterized by a change of 11-25 beats, and the bouncing rhythm - more than 25 beats per minute. Of all these parameters, a wavy rhythm is considered normal.

Deceleration and Acceleration

These terms, which are not understandable to everyone, are actually very easy to visualize - these are ups and downs (high and low episodes) on the graph. Expectant mothers also call them teeth and dips. In this case, elevations are called accelerations, and decelerations, respectively, are falls.

However, acceleration is not considered to be any increase in the heart rate of a child's heart, but only such at which the frequency increased by 15 or more beats per minute and lasted at this rate for 15 or more seconds. By analogy with this, deceleration is a decrease in the frequency by 15 or more beats while maintaining the tempo for 15 or more seconds.

The norm for a healthy and uncomplicated pregnancy is considered to be 2 or more accelerations in ten minutes of the study. Decelerations should not be normal. But single falls with normal other indicators will not be regarded as pathology.

Stirring fetus

This is the most controversial parameter of CTG, the norm of which is difficult to deduce in certain values.

In the third trimester, children already have their own individual temperament, and some babies are more active, while others prefer to sleep more and gain strength before the upcoming birth. That is why there is no strict regulatory framework that would regulate the number of movements of the baby in the mother's womb.

The baby's desire to move can be influenced by the weather, the time of day, and the personal phases of sleep and rest, as well as the mother's nutrition, her hormonal background and many other factors. Therefore, it is considered that the child is completely healthy if during the study he performs at least a few perturbations. For half an hour - three or more, for an hour - six or more.

It is important that the child not only demonstrates movements, but also shows a certain pattern between movements and accelerations., the so-called myocardial reflex. It is normal if each movement is accompanied by an increase in the heart rate.

Intense frequent movements may be a sign of hypoxia at the initial stage, rare movements may indicate that the baby is just sleeping or he has hypoxia in a neglected form. In general, this parameter in itself does not say anything and is always assessed only in combination with the rest of the CTG norms.

Contractions of the uterus

The strain gauge that surrounds a pregnant woman's abdomen during a diagnostic examination is sensitive enough to detect even small changes in abdominal circumference.

On the CTG, even those contractions are "drawn" that the expectant mother herself does not feel at the physical level. Contractile activity is measured as a percentage: the higher their value, the more likely the onset of labor.

So, labor contractions have a value of 98-100%, and training contractions are at the level of 75-80%. If the birth is still far away, and CTG showed 40%, there is no need to worry, these are normal natural contractions of the uterine muscles, which do not in any way affect the condition of the fetus.

Sinusoidal rhythm

Such a heart rate in a child is recorded quite rarely, and this cannot but rejoice, because the sinusoidal rhythm itself (when the graph looks like an alternation of sinusoids of the same height and duration) is a sign of the baby's serious condition.

According to medical statistics, about 70-75% of children who show a sinusoidal rhythm on CTG before birth, and it persists for 15-20 minutes, while the examination is underway, are born dead or die immediately after birth.

Sinusoids on the graph appear in babies with severe hypoxia, severe forms of Rh-conflict, serious intrauterine infections that pose a threat to the baby's life. Therefore, the conclusion, which says that sinusoidal rhythm = 0 min. means that the baby is okay.

Stress and non-stress tests

At the top of the CTG report, a woman can see the inscription "non-stress test". What this phrase means is quite simple to understand. The examination can be carried out as a standard, when the woman is at rest, and can be prescribed after physical exertion or the introduction of a small dose of the drug "Oxytocin" to the expectant mother, which causes contractions of the uterine muscles.

Conventional cardiotocography is performed in a non-stress mode. It is this fact that is reflected in the "non-stress test" record.

If doctors need to arrange additional tests for the baby, they will conduct CTG in a stress mode, but the parameters there will be completely different.

PSP

Opposite to this abbreviation in the conclusion about the passage of cardiotocography, there are the main values that are displayed by the program after analyzing all the above parameters. An indicator of the state of the fetus, this is how this value is deciphered - this is the final value.

The PSP rate is 1.0 or less. With such values, it is believed that the baby is comfortable enough, he does not have manifestations of hypoxia and other unsuccessful factors that can affect his well-being. If the conclusion indicates that the PSP exceeds the value of 1.1, but does not exceed 2.0, this indicates initial disorders in the state of the baby. Whatever these violations are, they are not considered life-threatening for the child. The expectant mother is recommended to visit CTG more often.

Dangerous are considered to be the PSP indicators higher than 2.1. If the values are in the range of up to 3.0, the woman should be hospitalized and additionally examined, since such indicators are often found in babies experiencing a severe Rh conflict or hypoxia in utero.

A PSP higher than 3.0 means mortal danger to the child. They will try to deliver the expectant mother as quickly as possible by making her a cesarean section so that the baby has a chance to survive.

Reactivity index

Under this phrase is an attempt to assess the nervous activity of the fetus during the study. The reactivity index is the ability of the fetus to respond to external stimuli. This value has a close relationship with the number of movements: the more the child moves, the larger the number may be (0.80, 1.0, etc.).

If a woman has no problems with the placenta and uterine blood flow, if the ultrasound did not show entanglement, then you should not pay attention to this index, since in itself, it is "technical information" that does not carry diagnostic value.

STV (short-term variation)

If a woman sees such a foreign abbreviation in her conclusion, do not be afraid. It is just a mathematical value that evaluates fast fluctuations (oscillations) in short periods of time. But if you really want to know what the STV rate is, we are ready to help you - the index should normally be more than 3 milliseconds.

If STV = 2.6 ms, experts estimate the risk of intrauterine injury and the probability of death of a child at 4%, but if the index drops even lower, the risks increase to 25%.

Score in points

Fischer scoring table

According to this table, popular in Russia, a child can receive a different number of points based on CTG results. If the baby scored 5 points or less, it is considered that he is in extremely distress, he is in danger of death.

If the scored number of points is from 6 to 8, there is a possibility of initial violations, but in general, the life of the baby is not in danger. If the child received 9-12 points, everything is fine with him.

Conclusions

Expectant mothers should not look for which of the parameters in her CTG conclusion are normal, and which deviate from it. All analysis for it is done with a special computer program. And the main indicator for a woman is PSP. In fact, it reflects the entire verdict.

If CTG did not work out, if the indicators contradict each other, the doctor will definitely ask you to come for the examination again. You should not worry, this is also not uncommon.

The alarming indicators of cardiotocography are not a reason to worry, but a reason to go to the hospital, where the expectant mother will be examined, including ultrasound and laboratory tests, and a decision will be made on delivery.

This option for the termination of pregnancy, of course, cannot suit any of the women. But in consolation we can say that at the time during which CTG takes place, the child is already quite viable, and born at 36, 37, 38 or 39 weeks, he may well cope with new circumstances.