Fetal CTG is the norm. Fetal CTG is normal at 36 weeks. How to decipher fetal CTG

2024 Author: Priscilla Miln | [email protected]. Last modified: 2023-12-16 00:21

Absolutely every woman during pregnancy worries about how her child develops, whether everything is in order. Today, there are methods that allow you to fairly reliably assess the condition of the fetus. One of these methods is cardiotocography (CTG), which reveals the relationship between fetal movements and heart rate. From this article you will learn what CTG is, by what characteristics it is evaluated, what indicators for fetal CTG are the norm, and what affects the results of the study.

What is CTG

Cardiotocography is based on recording the fetal heart rate and its changes depending on the influence of external stimuli or fetal activity.

Diagnosis is carried out using two ultrasonic sensors, one of which is fixed on the belly of a pregnant woman, having previously determined the area of good audibility of the baby's heartbeat.

It is designed to record fetal heart activity. The sensor perceives reflected from the heartthe child's ultrasound signal, which is further converted by the electronic system into an instantaneous heart rate. The second sensor is fixed on the abdomen in the fundus of the uterus. It registers uterine contractions. To improve the passage of ultrasonic waves, the sensors are treated with a special gel. Also, modern devices are equipped with a remote control, by pressing the button of which, a pregnant woman can note the movements of the fetus.

The results are displayed by the device on a paper tape in the form of a graph. It also displays uterine contractions and fetal movements. According to the data obtained, it is possible to judge, first of all, the state of the nervous system of the baby, his protective and adaptive reactions. If the fetal CTG indicators are normal, then the baby feels comfortable, and his development is proceeding according to the timing.

Why is CTG needed

Examination of a pregnant woman in the office of an obstetrician-gynecologist includes listening to the baby's heartbeat with a stethoscope. Deviation from the norm of the heart rate (HR) up or down indicates that the child is experiencing discomfort. In this case, the doctor sends the expectant mother for a more thorough study of the functioning of the fetal cardiovascular system - CTG.

There is a clear relationship between the well-being of a pregnant woman and the condition of the fetus. So, if the pregnancy proceeded calmly, without intrauterine infection, the threat of interruption, preeclampsia, then the results of CTG are likely to be normal. If, with a good he alth of the pregnant woman, there are suspiciousCTG results, it is necessary to repeat the examination in a week.

If a pregnant woman has serious changes in her state of he alth, then it is necessary to conduct CTG as often as possible in order to prevent the occurrence of pathologies in the development of the fetus in time and take the necessary measures.

Features of the study

CTG is usually prescribed after 32 weeks of pregnancy, since only by this time does the maturation of neuromuscular impulses occur, and the method becomes the most informative.

For example, for fetal CTG, the norm is 33 weeks - the presence of more than two accelerations on the chart. By this time, they are caused by the response of the nervous system to the movements of the fetus or to external factors. At earlier terms, accelerations may be associated with the conditions of intrauterine existence of the fetus, so the study may lead to false results.

Also, by this time, the fetus has a cycle of activity and rest, which is of great importance for this study. When conducting CTG during the resting period of the fetus, the results will always be positive, even if in fact there is a high degree of hypoxia. That is why the study should be carried out for at least 40 minutes. During this time, the fetus will definitely increase motor activity, which will allow you to register a change in heart rate during its movement.

It is very important that the woman feels calm and comfortable during the examination. Uncomfortable position or strong emotions can cause more active movement of the fetus, whichwill lead to false results. Usually, during the procedure, the woman sits in a comfortable chair or lies on the couch on her side.

In order to understand how to decipher the CTG of the fetus, we will analyze in detail what parameters it is evaluated by.

Basal Heart Rate

Basal HR is the average fetal heart rate calculated over 10-20 minutes. It is determined in the absence of fetal movement between uterine contractions without external stimuli, without taking into account accelerations and decelerations.

When conducting fetal CTG, the BHR rate is 110–160 beats per minute. Tachycardia, that is, an excess of the normal basal heart rate, can be observed with fetal hypoxia, anemia, malformations and insufficiency of the fetal heart function, as well as with a feverish state of a pregnant woman, the presence of an intrauterine infection, and increased thyroid function. Cardiac-stimulating drugs may increase the fetal heart rate.

A decrease in the basal level below normal (bradycardia) may be due to hypoxia, fetal heart defects, as well as low blood pressure of the mother, hypoxemia, prolonged umbilical cord compression, the presence of cytomegalovirus infection in a pregnant woman.

Heart rate variability

This parameter is characterized by the presence of instantaneous oscillations - deviations of heart rate from the basal level. When analyzing CTG, one usually studies the amplitude of instantaneous oscillations, according to the nature of which low oscillations are distinguished (deviationis less than three beats / min), medium (3–6 beats / min), high (amplitude more than 6 beats / min).

For fetal CTG, the norm is 36 weeks - high oscillations, indicating good he alth of the fetus. The presence of low oscillations indicates pathologies in its development.

Special attention in the analysis of cardiotocograms is paid to slow oscillations. Depending on their amplitude, a monotonous type is distinguished, which is characterized by a low amplitude of oscillations (from 0 to 5 beats / min), a transitional type with an amplitude of 6 to 10 beats / min, a wavy type (from 11 to 25 beats / min) and a jumping type. (amplitude above 25 beats / min). An increase in the amplitude of oscillations may be associated with moderate hypoxia of the fetus, as well as with the influence of external stimuli that stimulate its nervous system. A decrease in the amplitude of oscillations can be caused by severe hypoxia, which leads to inhibition of the function of the fetal nervous system, by the use of narcotic drugs, tranquilizers.

Accelerations

Acceleration is a temporary increase in heart rate of at least 15 beats / min compared to the basal level and a duration of more than 15 seconds. On a cardiotocogram, they look like tall teeth. Accelerations are a response to external stimuli, uterine contractions, and baby movements. Their presence on fetal CTG is the norm.

Decelerations

Deceleration is a decrease in the fetal heart rate by at least 15 beats per minute for more than 15 seconds. The graph is presented as significant depressions. Distinguish between early, late and variabledeceleration. In addition, they are classified by amplitude as light with a decrease in heart rate up to 30 beats / min, moderate - 30 - 45 beats / min, and severe - from 45 beats / min. A decrease in heart rate may occur due to impaired placental blood flow, myocardial hypoxia, umbilical cord compression.

Fetal CTG. Norm indicators

To assess the condition of the fetus, the World He alth Organization has developed recommendations that indicate the minimum and maximum allowable values for each of the parameters. According to these recommendations, fetal CTG (norm for 33 weeks) should have the following values:

• Basal heart rate: 110-160 bpm
• Heart rate variability between 5-25 beats/min.
• Two or more accelerations within 10 minutes.
• No deep decelerations.

It is worth noting that for fetal CTG, the norm for 35 weeks or more is the same as for 33 weeks.

Evaluation of the condition of the fetus by points

Decipher the results of CTG on a 10-point system, evaluating each criterion from 0 to 2 points. For CTG of the fetus, the norm of 36 weeks, as well as during the entire third trimester, is 9–10 points, if the total number of points is from 6 to 8, this indicates oxygen starvation (hypoxia) without emergency threats, it is necessary to repeat the CTG procedure in a week;

if 5 points or less, it means that the child is experiencing severe oxygen starvation, which can lead to serious neurological problems, urgent action is needed.

It must be remembered that even if the CTG of the fetus is 8 points or slightly lower, there is no need to be scared ahead of time. In this type of research, as well as in many others, there are factors that affect the information content of the testimony. The results are highly dependent, for example, on whether the child is sleeping or awake. Experienced doctors, when deciphering cardiotocograms, take into account such factors as weather conditions, the mood of a pregnant woman, and the level of glucose in a woman's blood. If the CTG data does not correspond to the norm, then the doctor will prescribe an additional examination. Usually, cardiotocography is performed twice in the third trimester of pregnancy, but in some cases more, for example, with multiple pregnancies, high blood pressure, infections, diabetes, poor ultrasound results, bleeding, premature contractions.

Possible errors in interpretation of CTG data

1. A baby in the womb is in constant motion. Sometimes he can press the umbilical cord with his head, because of which the blood flow in the vessels of the umbilical cord is disturbed for a short time, which is reflected in the results of CTG. In this case, the cardiotocogram will be pathological if the fetus is in good condition.
2. Sometimes, during oxygen starvation in the fetus, protective reactions are activated: there is a decrease in oxygen consumption by tissues and an increase in resistance to hypoxia. In such cases, the child suffers, but this does not affect the CTG.
3. With the development of pathology, the ability of tissues to perceive oxygen at its normal content inblood, due to which the fetus does not have any reaction, and the CTG will be normal, although he suffers from a lack of oxygen.

Given all of the above, you need to understand that fetal CTG during pregnancy is a very important diagnostic method, but to get a complete picture of what is happening, CTG data must be compared with data from other studies. To date, ultrasound diagnostics and dopplerometry are widely used.

Where can I do fetal CTG

CTG is done free of charge in all antenatal clinics. You can conduct a study in private medical centers, but on a paid basis.

Maternity hospitals also perform cardiotocography during childbirth. This helps to assess the well-being of the child in childbirth and uterine contractions, to check the effectiveness of the treatment and tactics of childbirth.

Some expectant mothers are afraid to conduct various kinds of research during pregnancy, believing that they can harm the he alth of the unborn baby. Cardiotocography is absolutely safe, and you can do it as many times as necessary, without risk to he alth. In addition, it is painless, does not cause any discomfort.

We wish you an easy pregnancy and good he alth!