During the period of carrying the child, the expectant mother learns many new letter abbreviations for herself - ultrasound, BPR, DBK, hCG. They become understandable and even familiar. In the last trimester, another "classified" diagnostic study in the letter code is assigned - CTG. Its implementation usually does not raise questions, but only a few can decipher the results. How to understand what is written in the conclusion of the CTG, we will tell in this material.
What it is?
Cardiotocography (this is how the name of the examination stands) is a non-invasive, safe and painless way to find out what condition the baby is in, how he feels. Such a survey is carried out, starting from 28-29 weeks of pregnancy. Most often, expectant mothers receive a referral to CTG at 32-34 weeks for the first time, and then the study is repeated just before the onset of the labor process.
During the birth itself, CTG is often used to determine if the baby has acute hypoxia during the passage through the birth canal.
If the pregnancy is going well, there is no need for additional CTG. If the doctor has concerns that it is proceeding with complications, then CTG is assigned individually, some have to take it weekly or even every few days. There is no harm from such a diagnosis either for the child or for the mother.
Cardiotocography allows you to find out features of the baby's heartbeat. A child's heart reacts immediately to any unfavorable circumstance, changing the frequency of its beating. In addition, the method detects contractions of the uterine muscles. Registration of changes occurs in real time, all parameters are recorded simultaneously, synchronously and displayed in graphs.
The first graph is a tachogram showing changes in the baby's heartbeat. The second is a graphic representation of uterine contractions and fetal movements. It is called a hysterogram or tocogram (women often use the abbreviation "toko"). The heart rate of the crumbs is determined by a highly sensitive ultrasound sensor, and the tension of the uterus and movements are captured by a tensometric sensor.
The data obtained is analyzed by a special program that displays certain numerical values on the research form, which we will have to decipher together.
Technique
An expectant mother should come to CTG in a calm mood, because any worries and experiences of a woman can affect the heartbeat of her baby. It is advisable to pre-eat, go to the toilet, because the examination takes quite a long time - from half an hour to an hour, and sometimes more.
You should turn off your cell phone, sit comfortably in a position that will allow you to spend the next half hour with comfort. You can sit down, lie on the couch, take a reclining position of the body, in some cases CTG can be performed even while standing, the main thing is that the expectant mother is comfortable.
An ultrasonic sensor is attached to the abdomen in the area of the child's chest, which will record the slightest changes in the heartbeat pattern and heart rate.
On top of it, a wide belt is put on - a tensimetric sensor, which will determine, by slight fluctuations in the volume of the expectant mother's abdomen, when the uterine contraction or movement of the baby has occurred. After that, the program turns on and the study begins.
At this stage, a pregnant woman may have two questions - what do the percentages on the fetal monitor mean and what the sounds that come during CTG say. We will help you figure it out:
- Sounds during research. The sound of a child's heartbeat, already familiar to the expectant mother, does not need an explanation. Earlier, ultrasound specialists have probably already let a woman listen to a small heart beating. During CTG, a woman, if the device is equipped with a speaker, will hear it constantly. Suddenly, a woman may hear a long, loud noise that looks like interference. This is how the child's movements are heard. If the device suddenly starts beeping, this indicates a loss of signal (the baby turned and moved significantly away from the ultrasonic sensor, the signal transmission was disrupted).
- Percentage on the screen. Percentages indicate the contractile activity of the uterus. The more actively the main female reproductive organ contracts, the more reason a doctor has for hospitalizing a woman. If the values are close to 80-100%, we are talking about the beginning of labor before childbirth. Indicators in the range of 20-50% should not scare a woman - it is definitely early to give birth to her.
Decoding the results
Understanding the abundance of numbers and complex terms is not as difficult as it seems at the first glance at the CTG result. The main thing is to understand and have a good idea of what concepts we are talking about.
Basal heart rate
Baseline, or basal heart rate, is the average value of your baby's heart rate. A mother who comes to CTG for the first time may be surprised that the crumbs' heart beats very unevenly, the indicators change every second - 135, 146, 152, 130 and so on. All these changes do not slip away from the program, and for the first ten minutes of the examination, it displays the average value, which for this baby will be the base or basal value.
This parameter in the third trimester does not change depending on the specific week, as some pregnant women think. And at 35-36 weeks, and at 38-40, the basal heart rate only reflects the average values of the frequency of the baby's heartbeat and in no way indicates either the gestational age or the sex of the child.
The norm of the basal heart rate is 110-160 beats per minute.
Variability
As you can understand from the sound of the word, this concept hides variants of something. In this case, options for deviation of the heart rate from the baseline values are considered. In medicine, another name for this phenomenon is used, which can also be found in the conclusion - oscillations. They are slow and fast.
Rapid ones reflect the slightest changes in real time, because, as already mentioned, each fetal heart beat displays a different heart rate. Slow oscillations are low, medium, and high. If in a minute of real time the frequency of contractions of the child's heart was less than 3 beats per minute, they speak of low variability and low oscillation. If the swing per minute was from three to six beats, then we are talking about the average variability, and if the fluctuations in one direction or another amounted to more than six beats, the variability is considered high.
To imagine this more clearly, let's give an example: in a minute the device registered a change in fetal heart rate from 150 to 148. The difference is less than 3 beats per minute, which means that this is low variability. And if the heart rate has changed from 150 to 159 per minute, then the difference is equal to 9 beats - this is a high variability. The norm for a healthy baby in an uncomplicated pregnancy is fast and high oscillations.
Slow oscillations are of several types:
- monotonous (heart rate changes by five or less beats per minute);
- transient (heart rate per minute changes by 6-10 beats per minute);
- wavy (heart rate changes by 11-25 beats per minute);
- galloping (more than 25 beats per minute).
If in a minute the heart rate jump looks like this: 140-142 beats / min, then we are talking about a monotonic slow oscillation, if in a minute the heart rate has changed from 130 to 160, then we are talking about a jumping slow oscillation. Wave-like oscillations are considered normal for a healthy baby, and other types almost always accompany various pathologies of pregnancy - cord entanglement, hypoxia, Rh-conflict.
Acceleration and deceleration
Quantitative change is oscillation, and qualitative change is acceleration and deceleration. Increased rhythm - acceleration. On the graph, this looks like a peak, a clove. A decrease in rhythm - deceleration, is graphically depicted as a peak with the top down, that is, a failure. Acceleration is an increase in the baby's heart rate by 15 beats per minute or more and maintaining this rhythm for more than 15 seconds.
Deceleration is a decrease in the heart rate value from the baseline value by 15 beats downward and maintaining this rhythm for 15 seconds or more.
There is nothing wrong with the accelerations themselves if more than two of them are registered in 10 minutes. However, too frequent accelerations, the same duration and occurring at regular intervals, are an alarm signal, the child is uncomfortable. Deceleration (reduction) is generally not characteristic of a healthy baby, but a small number of them with other normal cardiotocography parameters may be a variant of the norm.
Stirring
How many movements should be, the question is quite difficult, because there is no definite answer to it. All children have different physical activity, they are influenced not only by their own well-being, but also by factors that do not depend on it - the mother's nutrition, her mood and emotional state, and even the weather outside the window.
If the baby wants to sleep exactly at the moment when he needs to do CTG, his movements will be minimized.
Considered a good sign if at least several movements are recorded in the child during CTG: in half an hour - at least three, in an hour - at least six. Too frequent sharp movements are an alarming sign that may indicate violations in the state of the baby. Too infrequent movements are also not a very good indicator. However, if all other CTG values are normal, then the doctor will assume that the child has simply slept all this hour, and will ask the woman to come back for examination again in a few days.
It is not the movements themselves that are considered important, but the relationship between them and the number of accelerations. In a normal healthy child, movement increases the heart rate. If this connection is broken and perturbations are not accompanied by rises in heart rate, and the accelerations themselves arise spontaneously and are not associated with movement, the well-being of the crumbs is called into question. On the graph, the movements look like dashes in the lower part, where the uterine contractions are noted.
Uterine contractions
Uterine muscle contractions are depicted in the lower graph. Visually, they look like wavy drops, because the contraction begins smoothly and ends no less smoothly. They should not be confused with movements, they are marked with short vertical lines. Interestingly, the strain-gauge belt sensor records even those contractions that a woman does not physically feel.
Percentages represent contractile activity.
It is unambiguously impossible to determine the tone of the uterus on CTG, because the pressure inside the uterus can really be measured in only one way - to insert a thin long sensor-electrode into its cavity, but this is impossible until the fetal bladder is intact and labor has not begun. Therefore, the value of the tone of the uterus is constant - the base rate is taken as 8-10 millimeters of mercury. A program that analyzes all indicators, according to the contractility of the main female reproductive organ, can "conclude" that this pressure is exceeded. Only then can the doctor suspect a tone, but for confirmation, a manual examination on a gynecological chair and an ultrasound scan will be needed.
Sinusoidal rhythm
If the conclusion indicates "sinusoidal rhythm - 0 min", then this is a very good indicator. Such a rhythm, indicated on the graph as sinusoids repeating at equal intervals of time, of the same duration, speaks of severe pathologies. The number of accelerations and decelerations is minimal or absent altogether. If this graphical picture persists for about 20 minutes, doctors may suspect a big problem.
This rhythm occurs in children with severe uncompensated hypoxia, severe intrauterine infection, strong Rh-conflict. Seven out of ten babies who showed a sinusoidal rhythm on CTG for 20 minutes or more die in utero or immediately after birth.
Table of norms of basic indicators:
Assessment of fetal health - points
To assess the condition of the fetus, doctors use the methods of calculating the results in points. In women, well-grounded questions are often raised, which means 4 or 5-6 points on CTG, which can be indicated by 10, 11 or 12 points. Interpretation depends on which method of calculation the program operated or how the doctor calculated the result if the assessment was made “manually”.
The most commonly used grading system is Fischer.
This is a twelve-point system in which a certain number of points is awarded for each indicator.
By Fischer
Fischer scoring table (Krebs modification):
The interpretation of the results looks like this:
9,10, 11, 12 points - the child is healthy and feels quite comfortable, his condition does not cause concern;
6,7,8 points - the life of the baby is not in danger, but his condition raises concerns, since such an indicator may be a sign of initial pathological changes and adverse effects from the outside. A woman should do CTG more often in order to monitor the baby in dynamics;
5 points or less - the child's condition is threatening, there is a high risk of intrauterine death, stillbirth, neonatal death in the early postpartum period. The woman is sent to a hospital, where an urgent diagnosis is carried out, and in most cases it all ends with an emergency caesarean section to save the baby's life.
FIGO
This assessment table was adopted by the specialists of the International Association of Gynecologists and Obstetricians. It is less commonly used in Russia than the Fischer score, but it is more understandable for expectant mothers.
FIGO interpretation table:
PSP
This is a key value that is derived from all measured and analyzed parameters.
It stands for "an indicator of the state of the fetus."
It is very difficult to visualize by what algorithms and mathematical formulas this calculation takes place, if there is no mathematics diploma on the shelf at home. This is not required. It is enough for a mother-to-be to know which PSP indicators are considered the norm and what they mean:
Memory bandwidth less than 1.0. Such a result means that the baby is healthy, he is comfortable, his health and condition are not disturbed. This is a good result, in which the doctor lets the pregnant woman with CTG go home with a clear conscience, because nothing bad should happen to the baby.
Memory bandwidth from 1.1 to 2.0... This result indicates probable initial changes that differ from the normal state of health. Violations with such a PSP are not deadly, but they cannot be ignored. Therefore, a woman is asked to come to CTG more often, on average - once a week.
Memory bandwidth from 2.1 to 3.0. These indicators of fetal health are considered very alarming. They can indicate severe discomfort that the baby is experiencing in the womb. The cause of the baby's trouble can be Rh-conflict, a state of oxygen deficiency, entanglement with an umbilical cord, intrauterine infection. The pregnant woman is sent to the hospital. She is shown a more thorough examination and, possibly, an early delivery by cesarean section.
Memory bandwidth above 3.0. Such results may indicate that the child's condition is critical, he is threatened with intrauterine death, which can occur at any time.The woman is hospitalized urgently, an emergency caesarean section is shown to save the baby.
Stress and non-stress tests
The usual CTG, which is done during pregnancy, is considered a non-stress test. But sometimes the situation requires a more careful and detailed study of the peculiarities of the work of a small child's heart, for example, if the result of the previous CTG is unsatisfactory or if a child's heart is suspected, then stress tests are performed.
The study in this case is technically carried out in the same way as always, but before fixing the sensors on the belly of the expectant mother, she may be asked to walk up and down the stairs several times, breathe deeply and occasionally hold her breath during cardiotocography.
Sometimes, to understand how a child's heart and nervous system will behave in a stressful situation, a woman is injected with oxytocin, a drug that causes contractions of the uterine muscles.
Non-stress test excludes provoking external factors. A woman, on the contrary, is asked to calm down, sit comfortably, not think about anything alarming and bad. It analyzes how the baby's heart reacts to his own movements, that is, the number of accelerations is counted.
Deciphering stressful CTGs is the task of specialists, the conclusion of the analyzer program alone will not be enough, doctors must make allowances for the stress factor. A good result is a negative non-stress test in which the baby “shows” two or more accelerations in 40 minutes.
Possible problems
Problems that can be indirectly indicated by such an examination as cardiotocography can be different - from congenital malformations to pregnancy pathologies or external unfavorable factors that the woman herself is exposed to. But they will all be accompanied by one of the following deviations.
Tachycardia
This condition can be talked about if the basic heart rate exceeds the established norms, and the duration of the violation is 10 minutes or more. An increase in heart rate to 160-179 beats per minute indicates mild tachycardia. A severe form of tachycardia is when the baby's heart beats at a frequency of 180 beats per minute or higher.
The most common cause is fetal hypoxia. With oxygen deficiency, the child begins to experience stress, his hormonal background changes, because of this, the heart begins to beat faster. But this is only at an early stage of hypoxia. With severe oxygen deficiency, the baby behaves differently.
Tachycardia is often a companion of intrauterine infection that struck the baby. Almost like a born child, the baby in my mother's stomach can get sick. His immune defense will begin to work, and despite the fact that it is still very weak, the temperature will rise, and this will also immediately affect the heart rate. The reason for the child's tachycardia may be the unimportant state of health of his parent. If a woman's temperature rises, then the child's heart beats harder.
Also, the medications that the mother takes and any disturbances in her hormonal levels affect the fetal heart rate.
Bradycardia
If cardiotocography shows that the baby's heart beats below 100 beats per minute for 10 minutes or more, doctors diagnose bradycardia. This is a dangerous symptom that may indicate severe uncompensated hypoxia, in which oxygen deficiency is already critical, the child does not have the strength to move. If the slowdown in heart rate is recorded on CTG at the time of childbirth, then there is nothing dangerous in this, because with a decrease in heart rate, the baby reacts to passing through the birth canalwhen its head is pressed.
Fetal hypoxia
Oxygen starvation can be very dangerous for a child at any time, it leads to disorders of the central nervous system, and sometimes to fetal death. Early hypoxia, while it is still compensated by the protective mechanisms of the baby's body, is characterized by tachycardia, and late hypoxia, hypoxia in an advanced stage - bradycardia. In addition, CTG shows low variability, the same periodic acceleration, sinusoidal rhythm, monotony.
The memory bandwidth in this state of affairs is in the range of 1.1 - 3.0. And according to Fischer, the child's condition is estimated at 5-8 points, depending on the severity of oxygen deficiency. In severe hypoxia, urgent delivery is indicated, regardless of how long the pregnant woman is - at 37 weeks or only at 33 weeks. In any case, such a baby will have more chances to survive outside the mother's womb.
Could it be wrong?
Cardiotocography does not apply to high-precision diagnostic studies. Its accuracy is about 90%, moreover, much also depends on how correctly the examination is carried out, as well as on the doctor's experience and whether he will be able to correctly interpret the results. In general, CTG stands for everyone in the same way. But the reasons that led to deviations of certain normative values can be very diverse.
Therefore, it is impossible to treat the conclusion of the CTG as the ultimate truth. The survey only gives a general picture, but only additional diagnostics will help to confirm or deny negative results, as well as to establish the reasons for the baby's unusual behavior.
Usually these are laboratory blood tests, ultrasound scanning, ultrasound (Doppler ultrasound).
An erroneous CTG may be due to the fact that the woman did not prepare for the examination - she came sleepy, worried about personal problems. The veracity of CTG is also dubious if the pregnant woman took any medications and did not warn the doctor about it, because some drugs can significantly increase and decrease the heart rate of not only the mother, but also the fetus. An erroneous CTG can be in the event of a malfunction of the equipment on which the study is carried out.
Therefore, all dubious results must be rechecked with repeated CTGs, as well as with the help of ultrasound. All bad CTG results are also rechecked, but already in a hospital, so as not to risk the health of the mother and child.
