What is CTG and what does it show during pregnancy?

Cardiotocography, or CTG, is a pregnancy monitoring device that tracks the mother’s contractions and the baby’s heart rate. It offers crucial details regarding the health of the unborn child and can aid in the early detection of any possible problems.

In order to monitor the baby’s heartbeat and the frequency of uterine contractions, sensors are positioned on the mother’s abdomen during a CTG exam. The baby’s heart rate patterns and how they alter during contractions are depicted on a monitor using this data.

Physicians can evaluate the baby’s health and make sure everything is developing normally by having a clear understanding of the CTG results. In order to guarantee the safety of both mother and child, additional testing might be advised if there are any anomalies.

What is CTG?	CTG stands for Cardiotocography, a test that monitors the fetal heart rate and contractions of the uterus.
What does it show during pregnancy?	CTG shows the baby"s heart rate patterns, how the heart rate responds to contractions, and the overall well-being of the baby. It helps detect any potential issues early.

What is it?

Cardiotocography is a study that is hidden by the acronym CTG. It is essentially an ongoing, continuous recording of the child’s motor activity, uterine contractions, and the baby’s heartbeat. A recorder or computer program records each of these parameters simultaneously and instantly in real time on a calibration tape.

An ultrasound sensor records the heartbeat of the beating baby, while a strain gauge sensor records the contractions of the uterus.

A tachogram is the first type of graph, and a histogram is the second. CTG is currently the most widely used method of gathering information about a child’s condition, as there is only a few months left before birth, due to its simplicity, safety, and informativeness.

CTG is prescribed to all pregnant women registered at the antenatal clinic. In case of uncomplicated, normal pregnancy, the first examination is carried out between 30 and 32 weeks, then a similar examination is carried out immediately before childbirth in the maternity hospital during planned hospitalization. If the baby"s condition raises questions, then CTG can be carried out earlier, starting from 28-29 weeks. In case of serious pregnancy complications, the examination can be carried out daily. CTG is also used during the birth process itself. Examination during pregnancy, when sensors are placed on the abdomen of the expectant mother, is called external or indirect CTG. Direct cardiotocography is carried out when the integrity of the fetal membrane is broken, the waters have broken, and a thin electrode sensor is inserted directly into the uterus.

Cardiotocography, or CTG, is a pregnancy test that tracks the mother’s contractions and the baby’s heart rate. This easy, non-invasive procedure aids in the evaluation of the baby’s health and early identification of any possible problems by the medical team. CTG ensures that mother and baby receive the best care possible by monitoring how the baby’s heart rate reacts to contractions. This provides important insights into how the baby is handling the stress of labor.

What it shows?

With CTG, you can ascertain the baby’s emotional state. Initially, the gadget captures and shows the heart rate (HR), which is the primary indicator that lets you assess the infant’s health. An ultrasonic sensor generates an ultrasonic wave by utilizing the Doppler effect. It is transmitted back to the sensor after being reflected from tissues and moving blood cells in blood vessels. Consequently, the frequency at which the tiny heart beats becomes evident.

A strain gauge, a broad belt that encircles the expectant mother’s belly, measures the tone of the uterus and the movements of the fetus.

The abdomen will slightly change in volume if the uterus tenses or contracts, if the baby turns over, or if it stretches. This change will not elude the sensitive sensor and will be displayed on the graph right away. Additionally, the study has subtleties of its own that are crucial for an accurate diagnosis. Therefore, it’s crucial to pay attention to the baby’s heart rate as well as how it varies based on activity, movement, and other variables. Thus, the baby’s heart is evaluated for rhythm variability, myocardial reflex (the heart beats faster when moving), and any other periodic changes.

Indications for examination

• Any pregnancy pathologies. This includes gestosis, oligohydramnios and polyhydramnios, the threat of premature birth, infectious and non-infectious diseases that the expectant mother suffered during the period of bearing the baby, chronic illnesses that she has, high or low blood pressure in a woman, etc. .
• Strange behavior of the child. If the baby suddenly began to move rarely and sluggishly or, conversely, his motor activity increased.
• The appearance of abdominal pain in the mother. Any pain syndrome, of any nature and strength, necessarily requires CTG.

• Aggravated obstetric history. You should monitor the baby more often using cardiotocography if the woman"s previous pregnancies ended in premature birth, the death of the child in utero, as well as the birth of a child with gross developmental pathologies.
• Difficult previous births or cesarean section. If such facts took place in the past, then the next pregnancy in the later stages necessarily requires frequent monitoring, including with the help of CTG.

Pregnant women in the designated risk group may have multiple diagnostic examinations. The frequency is decided by a physician who is familiar with the unique aspects of a given woman’s pregnancy.

How it is carried out?

Any private clinic that provides pregnancy planning and management services, as well as the women’s clinic where you currently reside, can perform this straightforward examination. There are no unpleasant sensations associated with the procedure, and it is entirely painless.

The woman will be asked to settle in at the doctor’s office. The most important thing is that she feels comfortable, as CTG takes anywhere from 30 to 60 minutes, and sometimes longer if there are errors in the examination or if the results are unusual or dubious. She can lie down, sit down, or sit in a semi-sitting position.

A small ultrasound sensor, either round or rectangular in shape, is attached beneath a wide, special belt that is placed over the expectant mother’s stomach. The belt contains the same strain gauge sensor. The ultrasound sensor is positioned as near to the baby’s heart as feasible. The doctor will tighten the belt, adjust the sensors, and launch the computer program—which will start taking readings and creating graphs—as soon as he detects a noticeable rhythm. A recorder will be used to create the drawing if the examination is conducted using an outdated device.

An instrument called a strain gauge belt will track the movements. If a device is used for the diagnostics, the mother will be required to press a button in her hand each time she detects a distinct movement from her child. The program itself decides when to stop taking measurements; the "session" will end and the result printed as soon as the program receives the amount of data required to calculate the results.

Getting ready for CTG is really easy. It is best to get enough sleep and have a good night’s rest the day before to avoid distorted and untrustworthy results. You should avoid going to the examination without eating, as you will be required to sit still for a considerable amount of time. It is also advisable to use the restroom prior to visiting the doctor’s office. Since a sleeping fetus cannot exhibit the required motor activity, it is worthwhile to walk alongside the baby to "cheer up."

Reviews from expectant mothers suggest that waking up the baby is aided by a small chocolate bar eaten prior to the procedure.

Decoding and norms

In addition to providing results for each of the identified indicators right away following the examination, modern devices also assign points based on the overall health of the fetus. Later on, we will discuss the point assessment; for now, let’s just review the definitions of the key terms and their typical usage.

Basal rhythm

The tiny heart’s contraction frequency varies all the time. A woman’s first observation will be this. A parameter called the basal rhythm was derived in order to average the indicators, which range in beats per minute from 120 to 180. The device monitors variations in heart rate and shows the average basal value for the first ten minutes of the study. The line that reads "Basal rhythm" or "Basic heart rate" is where this is indicated. A base frequency of 110 to 160 beats per minute is thought to be the norm in the third trimester.

Rhythm variability

Those extremely fast fluctuating markers of the baby’s heart rate are variability if the basal rhythm is an average value. This parameter is referred to by the term "oscillations," which is a direct translation of "fluctuations."

Both rapid and slow oscillations are possible. Fast oscillations, also known as instantaneous oscillations, happen with every heartbeat in a baby. Because the heart beats every few seconds, the mother will be able to see them on the monitor as follows: 143, 156, 136, 124, 141, and so on.

Additionally, slow oscillations can differ. Low variability and low oscillations are indicated if the baby’s heart rate changes by less than three beats in a minute (it was 140, it is now 142). Average variability is when there is a 3 to 6 beat-per-minute change in heart rate (e.g., 140 to 145). When the heart rate fluctuates by more than six beats per minute (e.g., from 140 to 150), we are discussing high oscillations and high variability.

Elevated and immediate oscillations are regarded as typical.

The baby may have major pathological conditions if the device detects low variability and instantaneous oscillations in the child. This is frequently seen in cases of hypoxia.

Slow oscillations can be wave-like (heart rate changed by 11–25 beats in 1 minute), transient (rhythm changed by 6–10 beats), monotonous (heart rate changed by no more than five beats per minute of the study), and jumping (more than 25 beats per minute). Waves that move slowly are regarded as typical oscillations. Any additional slow fluctuations are considered concerning symptoms. Particularly when the baby’s umbilical cord is wrapped around it, jumping happens, and transitional jumping happens when there is hypoxia.

Accelerations and decelerations

On the graph, these are the same "teeth" and "dips" that expectant mothers talk about. Accelerations are simply defined as a baby’s heart rate rising by more than 15 beats per minute and staying at that level for at least 15 seconds. This represents an increase on the graph. A deceleration occurs when the beat rate is maintained for at least 15 seconds while the rhythm is slowed down by the same 15 beats per minute. These appear to be a dip on the graph.

Two or more accelerations per ten minutes are regarded as typical. Fetal distress may be indicated if the "peaks" on the graph repeat at the same rate and for the same length of time. Decelerations are in no way regarded as typical. Usually, they suggest hypoxia, but slight "dips" could also be a typical variation; it all depends on the other CTG readings.

Fetal movements

Many expectant mothers believe that the number of baby movements per hour is the main parameter that determines CTG. This is not so. At least because there is no standard for the number of movements a child can make per hour. It is conventionally considered a good sign if the baby makes 6-8 or more movements during the hour of diagnostics. The number of movements can be affected by the mother"s mood at the time of the CTG, and what she ate, and how her metabolism is going. The baby may be alert, or he may want to sleep. Therefore, the number of movements is looked at only in conjunction with the rest of the diagnostic results.

On the graph beneath the fetal cardiogram graph, contractions of the uterine muscles appear as smooth, wavy lines.

There are movements there, but they resemble sharp peaks and rises.

Few movements can be a sign of a serious illness, such as oxygen deficiency, as well as that the infant is sleeping or in a resting phase. However, based just on one of these indicators, no inferences can be made.

The tone of the uterus

Many expectant mothers worry about whether uterine hypertonicity or CTG tone will reveal CTG. Answering it is not as simple as it sounds. As previously stated, there are two methods for performing CTG: internal and external. The discussed external method is unable to definitively determine whether a woman has an increased tone. It can only be used to adjust individual uterine contractions.

Only by inserting a thin electrode-sensor into the uterus can one accurately measure the pressure inside the cavity, which rises with tonic contractions. This is not feasible during pregnancy if the fetal bladder is secure and undamaged, for obvious reasons. Additionally, since the baby is ready to "go out" during childbirth, there is typically no need for this kind of measurement. Instead, external CTG measurements, which reveal the baby’s heartbeat and activity, are informative.

As a result, 8 to 10 millimeters of mercury are thought to be the standard intrauterine pressure.

When evaluating the uterus’ contractility, the program discusses tone—but it does so subtly and with great care.

Contractions – true and false

On the CTG graph, contractions—which are the uterine muscles contracting—are visible. Furthermore, false or training contractions occur prior to the start of labor, sometimes even well in advance of the actual contractions that accompany the birthing process. Real contractions are represented on the graph as fairly large waves in the bottom line. The training will have a similar appearance, but the "waves" won’t be as noticeable, and each wave will last no longer than one minute.

Simplifying everything above allows us to see the CTG norms, which at this point allow us to declare that the child is doing well. The table below illustrates this:

Sudden, intense oscillations,

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

Possible disorders and their causes

Similar to any other diagnostic test, CTG, or rather its findings, can cause a lot of confusion, particularly if the physician declares that "CTG is bad." We’ll explain which pathologies are detectable below.

Sinusoidal rhythm

A CTG graph that looks like smooth identical sinusoids typically makes specialists very pessimistic. It is true that this occurs extremely infrequently; out of 300–350 examinations, only one woman may display a sinusoidal rhythm on cardiotocography.

There are no accelerations or decelerations (rises and falls) on the graph, and the basic heart rate is fairly normal with variability under 15 beats per minute. Typically, a graph like this is not encouraging. This is the behavior of a child who has a severe Rh conflict (meaning there is significant fetal hypoxia) when the pregnant woman and the unborn child are poisoned with drugs or other toxic substances.

The child is at greater risk if the mother has not used drugs or poisons. In this instance, a sinusoidal rhythm may indicate impending death. About 70% of infants with such sinusoids on CTG were stillborn or passed away within the first few hours of life for a variety of causes.

To assess whether the rhythm is sinusoidal, as in the image, the graph needs to be "drawn" for at least 20 minutes. In this instance, the mother is taken to the hospital immediately in order to attempt an emergency cesarean section and save the child’s life.

High fetal heart rate

Fetal tachycardia is diagnosed when there is a discernible increase in the baby’s heart rate on the CTG for ten minutes, and the base heart rate regularly rises above normal. In this instance, the degree to which the fundamental values are surpassed is highly significant:

• HR = 160-179 bpm – mild tachycardia;
• HR = 180 bpm and higher – severe tachycardia.

A small heart may beat so frequently for a variety of reasons. Tachycardia typically indicates a lack of oxygen. Remedial mechanisms that are intended to flood tissues and organs with oxygen "for future use" are "turned on" when an infant does not get enough oxygen. Stress hormones start to cause the heart to beat more quickly.

A fetus may react to a fever by racing their heart rate. The baby’s heart rate will spike right away if the mother’s temperature reaches at least 37.5 or 38.0 degrees. A baby infection could be the cause of this CTG if the mother is well and does not report a rise in body temperature. When an intrauterine infection occurs, the baby’s immunity starts to produce antibodies and other auxiliary substances that raise the child’s body temperature and quicken its heartbeat.

It is important to let the doctor know if the mother took any medications recently before the exam.

Elevated heart rate is one of the side effects of certain medications, and not just in the mother. It is possible to observe tachycardia in children whose mothers are experiencing thyroid dysfunction. In this instance, the mother’s aberrant hormonal background has an impact on the baby’s body.

Slow fetal heartbeat

Bradycardia is the term used to describe a baby’s heart rate falling below normal. The heart rate is deemed to be an alarming indicator if it stays at 100 beats per minute or lower for 10 minutes or longer during the examination.

Severe hypoxia can cause a slow heart rate and actually endanger the life of the baby. These signs during delivery show that the baby’s head was compressed as it passed through the birth canal. In the second scenario, bradycardia—also referred to as reflex arrhythmia—is regarded as a typical variation. The baby’s heart rate may also be slowed down by certain drugs the mother took the day before the exam.

Monotonic heartbeat

When slow fluctuations, or oscillations, do not exceed five beats per minute, a disorder of this kind can be discussed. The graph doesn’t show any abrupt changes. The woman will undoubtedly be offered to undergo further testing, such as an ultrasound with ultrasound dopplerography, if the graph stays this way for the full ten to fifteen minutes of the examination. This is because monotony typically "signals" hypoxia and other unfavorable circumstances for the baby.

Fetal hypoxia – oxygen starvation

Every expectant mother is aware of the perilous and sneaky nature of hypoxia. Through the "mother-placenta-fetus" system, the baby receives oxygen from the mother’s blood, which can cause an oxygen shortage that can cause irreversible brain damage or even cause the baby to die.

A baby’s heart rate may drop or rise during a cardiotocographic examination, which could be indicators of hypoxia.

Early oxygen starvation causes the heart to beat more quickly than is normal; late hypoxia causes a decrease in heart rate, or bradycardia.

A baby with oxygen deficiency, which is critical for proper development, will "demonstrate" low variability on CTG, with accelerations that are exactly the same in terms of duration and severity, a sinusoidal rhythm, and frequent, sharp movements that medical professionals refer to as "painful movements."

The woman is sent for further testing if CTG finds any of these symptoms. However, the expectation of an early cesarean section and hospitalization of the expectant mother are predicated on the identification of two or more concerning indicators.

Scoring

The cardiotocography results are summarized using a scoring system. A very precise number of points are calculated during the evaluation of each of the aforementioned parameters, and these points add up to the final result. In the field of obstetrics and gynecology, points are assigned based on multiple criteria.

Fisher scale

This approach is still regarded as the most precise and accurate of all the methods used to calculate the results. Four primary values are evaluated when calculating points on the Fisher scale: the fundamental heartbeat, variability, accelerations, and decelerations. Dr. Krebs added to this scale and suggested accounting for the quantity of fetal movements. As a result, the following method of calculating points was discovered:

Krebs’s modified Fisher scale evaluation table:

Indicator determined on CTG	1 point is awarded provided that:	2 points are awarded provided that:	3 points are awarded provided that:
Basic heart rate	Less than 100 bpm or more than 100 bpm	100-120 bpm or 160-180 bpm	121-159 bpm
Severity of slow oscillations	Less than 3 bpm	From 3 to 5 bpm	From 6 to 25 bpm
Number of slow oscillations	Less than 3 during the study period	From 3 to 6 during the study period	More than 6 during the study period
Number of accelerations	Not recorded	From 1 to 4 per half hour	More than 5 per half hour
Decelerations	Late or variable	Variable or late	Early or not recorded
Movements	Not recorded at all	1-2 per half hour	More than 3 per half hour

For the fetus, a normal score on this scale is regarded as 9–12 points. This indicates that, at least during the study period, the infant is feeling good about herself.

Fisher states that if the CTG result is between 6 and 8 points, the mother should have additional CTG monitoring as this could indicate that the child is not doing well. It does not, however, immediately endanger the baby’s life. It is advised to monitor the dynamics by repeating CTG more frequently.

Fisher states that an indicator with fewer than five points is the most concerning. This indicates that the child is extremely vulnerable and could die at any time. When you receive such CTG results, you are usually sent straight to the hospital, where you must make a decision on an early delivery within the next few hours in order to give the baby the best chance of survival. In this particular instance, even a very premature birth puts the child in greater danger than the child staying in the mother’s womb.

FIGO scale

The International Association of Gynecologists and Obstetricians developed this scale in an effort to "equalize" some of the errors that physicians from various nations may have made when evaluating the CTG criteria. The global "gold standard" is this.

Table of assessment for the FIGO scale:

Indicator found using CTG

Normal CTG value

Value for "suspicious" or dubious CTG

Significance within the field of pathology

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

Cardiotocography, or CTG, is a straightforward but efficient method of keeping an eye on the mother’s and the unborn child’s health during pregnancy. It aids medical professionals in determining the baby’s heart rate and possible labor stressors.

By assuring expectant mothers that the baby is healthy inside the womb, this test provides comfort. Medical professionals can respond promptly to any concerns that may arise.

In the end, CTG is a useful instrument that promotes a healthy pregnancy and gives the medical staff and parents peace of mind.

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