Decoding CTG during pregnancy

Expectant mothers go through a number of tests and procedures in order to guarantee the health of their unborn child. Cardiotocography is one of these crucial tests (CTG). It provides information about the health of the unborn child inside the womb by assisting doctors in monitoring the baby’s heartbeat and movements.

Although the CTG test is simple to administer, it can be difficult to interpret the results. Parents may be left wondering what all the lines and numbers on the printout mean. Deciphering the CTG, however, can reveal important details regarding the baby’s health.

We’ll explain what a CTG test is, how it operates, and what the findings mean in this post. Whether you’re trying to understand your results or getting ready for your first CTG, this guide will help make things more understandable.

What is it?

The examination, known as cardiotocography, is a non-invasive, painless, and safe method of determining the baby’s condition and emotional state. This assessment is conducted beginning in the 28th and 29th week of gestation. Pregnant women are typically referred for CTG for the first time between weeks 32 and 34, and the test is then repeated right before labor begins.

CTG is frequently used during labor to assess if the baby is experiencing acute hypoxia while passing through the birth canal.

Further CTG is not necessary if the pregnancy is progressing well. CTG is prescribed on an individual basis if the physician is concerned that complications are developing. Some patients are required to undergo CTG every week or even every few days. Such diagnostics do not pose any risks to the mother or the child.

Cardiotocography allows you to find out the features of the baby"s heartbeat. A child"s heart reacts to any unfavorable circumstances immediately, changing its heart rate. In addition, the method determines 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 image of uterine contractions and fetal movements. It is called a hysterogram or tocogram (women often use the abbreviation "toco"). The baby"s heart rate is determined by a highly sensitive ultrasound sensor, and the tension of the uterus and movements are captured by a strain gauge.

A unique program analyzes the acquired data and outputs specific numerical values on the research form, which we will jointly interpret.

Technique of implementation

The expectant mother should come to the CTG in a calm mood, because any worries and experiences of the woman can affect the heartbeat of her baby. It is advisable to eat and go to the toilet beforehand, because the examination lasts 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 in comfort. You can sit down, lie down on a couch, take a semi-recumbent body position, in some cases, CTG can even be performed standing, the main thing is that the expectant mother is comfortable.

The spot on the stomach where the child’s chest fits is equipped with an ultrasound sensor that records even the smallest variations in the type and pace of the heartbeat.

A tensiometric sensor, a wide belt, is placed on top of it to detect when a uterine contraction or baby movement has occurred based on minute variations in the volume of the expectant mother’s abdomen. Following this, the study is launched and the program is activated.

• Sounds during the study. The sound of the baby"s heartbeat, already familiar to the expectant mother, does not need an explanation. Previously, ultrasound specialists have probably already let a woman listen to a little heartbeat. During CTG, a woman, if the device is equipped with a speaker, will hear it constantly. Suddenly, a woman may hear a long loud sound, similar to interference. This is how the baby"s movements are heard. If the device suddenly starts beeping, this indicates a loss of signal (the baby has turned and moved significantly away from the ultrasound sensor, the signal transmission has been disrupted).
• Percentages on the screen. Percentages indicate the contractile activity of the uterus. The more actively the main female reproductive organ contracts, the more grounds the doctor has for hospitalizing the woman. If the values ​​are close to 80-100%, we are talking about the onset of contractions before childbirth. Indicators within 20-50% should not frighten a woman – it is definitely too early for her to give birth.

Decoding of results

Despite what might appear upon first glance at the CTG result, it is not as difficult to understand the abundance of numbers and complex terms. Understanding and having a solid understanding of the concepts we are discussing are crucial.

Basal heart rate

The average heart rate of a baby is known as their basal or basal heart rate. When a mother sees a CTG for the first time, she might be shocked to see how wildly the baby’s heart beats and how the numbers, which range from 130 to 146 to 152, change every second. The program does not break from any of these modifications, and within the first ten minutes of the test it shows an average value, which for a particular baby will be the basic or basal.

Contrary to what some pregnant women believe, this parameter does not change during the third trimester based on the particular week. The basal heart rate at 35–36 weeks and 38–40 weeks simply represents the average heart rate of the baby and is not indicative of the child’s sex or gestational age.

The basal heart rate typically ranges from 110 to 160 beats per minute.

Variability

The word’s pronunciation makes it clear that this idea conceals variations of something. In this instance, we take into account the possibilities for heart rate deviation from the initial values. This phenomenon is also referred to as oscillations in medicine, a term that is used in the conclusion. They have a range of speeds.

As previously mentioned, each heartbeat of the fetus represents a distinct heart rate, so fast ones capture the smallest changes in real time. Two types of slow oscillations are medium and high. They refer to a child’s heart as having low variability and low oscillation if it beats less than three times per minute in real time. We are discussing average variability if the range per minute was between three and six beats; if the variations were greater than six beats, the variability is regarded as high.

Let’s use the following example to help you understand this better: the device detected a change in the fetal heart rate from 150 to 148 in just one minute. There is little variability because the difference is less than three beats per minute. Additionally, there would be a 9-beat difference if the heart rate went from 150 to 159 in a minute; this indicates high variability. Fast and high oscillations are typical for a healthy baby born during a straightforward pregnancy.

There are various kinds of slow oscillations:

• monotonic (heart rate changes by five or less beats per minute);
• transitional (heart rate changes by 6-10 beats per minute in a minute);
• wave-like (heart rate changes by 11-25 beats per minute);
• jumping (more than 25 beats per minute).

We are discussing a monotonous slow oscillation if the heart rate increases by 140–142 beats per minute in a minute, or a jumping slow oscillation if it increases by 130–160 beats per minute. While wave-like oscillations are thought to be typical for a healthy baby, other kinds nearly invariably accompany different pregnancy pathologies, such as Rhesus conflict, hypoxia, and umbilical cord entanglement.

Accelerations and decelerations

Oscillations are a quantitative change, while accelerations and decelerations are a qualitative change. Acceleration is the rise in heart rate. This appears as a jagged line, or a peak, on the graph. Heart rate slowing is deceleration, which can be visually represented as a dip or a peak with the top down. When a baby’s heart rate increases by 15 beats per minute or more and stays at this level for longer than 15 seconds, this is known as acceleration.

A heart rate that decelerates is one that drops by 15 beats from its baseline and stays in that rhythm for at least 15 seconds.

If two or more accelerations are recorded in a 10-minute period, there is nothing wrong with the accelerations per se. On the other hand, excessively frequent accelerations that are of the same length and happen at regular intervals indicate that the child is uncomfortable. In theory, a healthy baby does not exhibit deceleration (decrease), but a small percentage of them may deviate from the norm if they also exhibit other normal cardiotocography indicators.

Movements

The question of how many movements is rather difficult to answer because there isn’t one right number. Every child has a different level of motor activity, and in addition to external factors like the mother’s diet, her emotional state, and even the weather, they are also influenced by their own well-being.

The infant’s movements will be minimal if he chooses to sleep right before a CTG is required.

If the child records at least a few movements during the CTG—at least three in a half-hour, or at least six in an hour—that is regarded as positive indication. An concerning indication of potential disturbances in the baby’s condition is an excessive frequency of sharp movements. Additionally, too few movements are not a very good indicator. In the event that all other CTG readings are normal, the doctor will request that the woman return for another examination in a few days, assuming that the child has simply fallen asleep for the entire hour.

The relationship between the movements and the quantity of accelerations is more significant than the movements per se. A child in normal health experiences an increase in heart rate when they move. Should this link be severed, the baby’s health is questioned if the movements don’t coincide with heart rate increases and the accelerations happen on their own without any connection to movement. The movements in the graph’s lower section, where uterine contractions are shown, resemble dashes.

Uterine contractions

The lower graph displays uterine muscle contractions. Because of the smooth beginning and ending of the contraction, they appear visually to be wave-like changes. The short vertical dashes that are used to indicate them should not be confused with movements. It’s interesting to note that the strain gauge belt records contractions even when the woman is not experiencing physical pain.

Contractile activity is indicated by percentages.

It is impossible to determine the tone of the uterus with CTG, because the pressure inside the uterus can only be measured in one way – by inserting a thin long sensor-electrode into its cavity, but this is impossible until the amniotic sac is intact and unharmed, and labor has not begun. Therefore, the value of the uterine tone is constant – 8-10 millimeters of mercury are taken as the basic norm. A program that analyzes all the indicators, based on the contractility of the main female reproductive organ, can "conclude" that this pressure is exceeded. Only then can the doctor suspect tone, but for confirmation, a manual examination on a gynecological chair and ultrasound will be needed.

Sinusoidal rhythm

It’s a strong indication if the conclusion says "sinusoidal rhythm – 0 min." Severe pathologies are indicated by a rhythm like this, which is represented on the graph as sinusoids repeating at equal intervals of time and duration. There are either very few or none at all accelerations and decelerations. Physicians may suspect serious issues if such a graphic picture lasts for more than twenty minutes.

Children with severe intrauterine infections, severe Rh conflicts, or severe uncompensated hypoxia experience this kind of rhythm. When a baby has a sinusoidal rhythm on a CTG for 20 minutes or longer, seven out of ten of them pass away during pregnancy or shortly after birth.

Normative table for the primary indicators:

Measured parameter

Typical value

Baseline heart rate

120–180 bpm when moving, and 108–160 bpm when at rest.

Sudden, intense oscillations,

General variability, slow wave-like oscillations, 5–25 bpm

Not more than 15 beats per minute, at least twice during each exam

Not present or not more than 15 bpm

Six or more times per hour

Assessment of fetal condition – points

Doctors use methods for calculating results in points in order to evaluate the fetus’s condition. It’s normal for women to wonder what 4 or 5 or 6 CTG points mean, or what 10 or 11 or 12 points can mean. The program’s calculation method or the doctor’s method, if the assessment was completed "manually," will determine how the result is interpreted.

The Fisher scoring system is the one that is most frequently applied.

Each indicator is given a specific number of points in this twelve-point system.

According to Fischer

Fischer scoring table (modified by Krebs):

Indicator found using CTG

One point is given if

Two points are given if

You receive three points if:

Either 100 bpm or more per minute

Either 160–180 bpmor 100–120 bpm

The degree of sluggish oscillations

Between three and five beats per minute

Between 6 and 25 beats per minute

Quantity of sluggish oscillations

During the study period, less than three

During the study period, from 3 to 6.

Over six during the course of the study

From 1 to 4 in thirty minutes

More than five in thirty minutes

Erratic or delayed

Erratic or delayed

Early or not documented

Not at all recorded

More than three in thirty minutes

The following is how the results are interpreted:

• 9,10, 11, 12 points – the child is healthy and feels quite comfortable, his condition does not cause concern;

• 6,7,8 points – the baby"s life is not in danger, but its condition is worrisome, since such an indicator may be a sign of initial pathological changes and adverse external influences. A woman should do CTG more often to monitor the baby dynamically;
• 5 points or less – the baby"s condition is life-threatening, there is a high risk of intrauterine death, stillbirth, neonatal death in the early postpartum period. The woman is sent to the hospital, where urgent diagnostics are carried out and in most cases everything ends with an emergency cesarean section to save the baby"s life.

According to FIGO

Experts from the International Association of Gynecologists and Obstetricians have approved this evaluation table. Though less common than the Fisher assessment in Russia, it makes more sense for expectant mothers.

Table of interpretation for FIGO:

Parameter established throughout the research

Worth: "norm"

Interpretation: "dubious" or "suspicious"

Pathology is the value.

Or between 151 and 170 bpm

100 bpmor greater than 170 bpm

Within 40 minutes, 5–10 bpm

Sinusoidal rhythm or less than 5 bpm in 40 minutes

Two or more times within forty minutes

Not present for a forty-minute assessment

Not at all registered or a rare variable

Erratic or delayed

PSP

Based on every parameter that has been measured and examined, this key value has been determined.

The term refers to a "fetal condition indicator."

Unless you happen to have a diploma in mathematics lying around your house, it is very difficult to picture the algorithms and mathematical formulas used to perform this calculation. This is not necessary. The expecting mother only needs to understand which PSP indicators are typical and what they imply:

• PSP less than 1.0. This result means that the baby is healthy, comfortable, his well-being and condition are not violated. This is a good result, in which the doctor lets the pregnant woman go home with a clear conscience after the CTG, because nothing bad should happen to the baby.
• PSP from 1.1 to 2.0. This result indicates probable initial changes that differ from normal well-being. Violations with such PSP are not life-threatening, but they cannot be ignored. Therefore, a woman is asked to come to CTG more often, on average – once a week.

• PSP from 2.1 to 3.0. Such indicators of the fetus"s condition are considered very alarming. They can indicate severe discomfort that the child is experiencing in the mother"s womb. The cause of the baby"s distress can be a Rh conflict, a state of oxygen deficiency, umbilical cord entanglement, intrauterine infection. The pregnant woman is sent to the hospital. She is shown a more thorough examination and, possibly, early delivery by cesarean section.
• PSP above 3.0. Such results may indicate that the child"s condition is critical, he is threatened with intrauterine death, which can happen at any time. A woman is hospitalized urgently, an emergency cesarean section is indicated to save the baby.

Understanding the crucial information this test provides regarding the baby’s heart rate and the mother’s uterine contractions is key to deciphering CTG (cardiotocography) during pregnancy. In order to make sure the infant is not in distress, it helps the doctors keep an eye on its wellbeing. The results provide clear insights into whether the pregnancy is progressing healthily or whether there are concerns that require immediate attention, even though the graph may appear complicated.

Stress and non-stress tests

When performed during pregnancy, a routine CTG is regarded as a non-stress test. However, there are instances when the circumstances call for a more thorough examination of the characteristics of a small child’s heart. For instance, stress tests may be conducted if the child’s heart defects are suspected or if the results of the previous CTG are not satisfactory.

Technically, the study is conducted exactly as it always is in this instance, but prior to the expectant mother having sensors attached to her stomach, she might be asked to walk up and down the stairs multiple times, breathe deeply, and occasionally hold her breath during the cardiotocography.

Sometimes, a woman receives an injection of oxytocin, a medication that causes contractions in the uterus, to help her understand how her child’s heart and nervous system will respond in a stressful scenario.

An exam without stress eliminates aggravating outside variables. On the other hand, the woman is asked to settle in, find a comfortable position, and stop thinking of anything unsettling or negative. The baby’s heart’s response to its own motions is examined; specifically, the quantity of accelerations is tallied.

Understanding stress Specialists perform CTG; the results of the analyzer program by themselves are insufficient, and physicians must adjust for stress. A negative non-stress test, in which the infant "shows" two or more accelerations in forty minutes, is considered a successful outcome.

Possible problems

Exams like cardiotocography can be used to indirectly identify a variety of problems, including congenital malformations, pregnancy pathologies, and externally induced adverse factors that the woman may be exposed to. However, each of them will come with one of the subsequent deviations.

Tachycardia

If the violation demonstration lasts for ten minutes or longer and the baseline heart rate is higher than the accepted norms, this condition can be discussed. An increase in heart rate to 160–179 beats per minute is indicative of mild tachycardia. When a baby’s heart beats 180 beats per minute or more, it is considered severe tachycardia.

A common cause is hypoxia in the womb. A child who is oxygen deficient starts to feel stressed, which alters their hormonal background and causes their heart to beat more quickly. However, this is just while hypoxia is just beginning. The infant acts differently when there is a severe oxygen shortage.

When the baby has an intrauterine infection, tachycardia frequently coexists. The unborn child can become ill in the mother’s womb, much like a born child. His immune system will kick in, and even though it’s still very weak, the temperature will rise, which will instantly raise the heart rate. The child’s mother’s ill health may also be the reason for his tachycardia. The child’s heart beats more quickly when the mother has a fever.

The mother’s medications and any hormonal imbalances have an impact on the fetus’s heart rate as well.

Bradycardia

Doctors diagnose bradycardia if a cardiotocography reveals that the baby’s heart beats for 10 minutes or longer at a rate of less than 100 beats per minute. This is a dangerous symptom that could mean the child has severe uncompensated hypoxia, where their oxygen deficiency is so severe that they are unable to move. There is nothing dangerous about a slowdown in heart rate seen on CTG at birth; the baby’s heart rate lowers in response to pressing its head, which helps it pass through the birth canal.

Fetal hypoxia

At any age, oxygen starvation can be extremely dangerous for children because it can cause CNS disorders and occasionally even result in the fetus’s death. Tachycardia is the hallmark of early hypoxia, when the baby’s body is still compensating for it, and bradycardia is the hallmark of late hypoxia, which is hypoxia at a more advanced stage. Furthermore, CTG exhibits monotony, sinusoidal rhythm, low variability, and the same periodic accelerations.

In this case, PSP falls between 1.1 and 3.0. Fisher also states that the child’s condition is graded from 5-8 points based on how severe the oxygen deficiency is. It is necessary to deliver the baby immediately in the event of severe hypoxia, whether the baby is 37 weeks along or only 33 weeks along. Anyhow, the baby’s chances of surviving outside the mother’s womb are higher.

Term	Explanation
Baseline heart rate	The average heart rate of the baby, usually between 110-160 beats per minute.
Variability	The small changes in the baby"s heart rate, showing how well the baby is coping.
Accelerations	Brief increases in the baby"s heart rate, which are a good sign of well-being.
Decelerations	Temporary drops in the baby"s heart rate, which can be normal but sometimes indicate stress.
Contractions	Shows the frequency and strength of the mother"s uterine contractions.

By assuring the health of the unborn child, parents can feel more at ease when they are aware of their CTG results during pregnancy. With the assistance of your healthcare provider, even though the numbers and graphs may initially seem overwhelming, it becomes easier. Never be afraid to inquire about the meaning of each section of the test.

It’s crucial to keep in mind that CTG is only one method of keeping an eye on your baby’s health. When assessing the pregnancy, your doctor will take a variety of factors into account because sometimes a single result doesn’t tell the whole story.

Have faith in your medical team and your body. You’ll be more equipped to handle any situation that may come up if you have the correct information and support.

Video on the topic

CTG Decelerations

Cardiotocography. Basics of the method

Interpretation of a normal cardiotocogram

Cardiotocography (CTG) of the fetus | Decoding CTG in norm and in pathology | Lectures on obstetrics

33-34 weeks. CTG. Fetal growth rate per day.