Registration of changes in the number of fetal heartbeats simultaneously with changes in the contractile activity of the uterus and fetal movements on paper using electronic equipment is called cardiotocography (CTG).
What is CTG?
CTG is the most commonly used and accessible method monitoring the condition of the fetus along with ultrasound (ultrasound) and is a continuous simultaneous registration of frequency heart rate fetus (heart rate) - cardiotachograms and uterine tone - tocograms.
Sensor locations
Used for CTG during pregnancy special apparatus- cardiac monitor. Fetal cardiac activity is recorded using a special ultrasound sensor. It is fixed on the anterior abdominal wall of a pregnant woman in the area of best audibility of fetal heart sounds, which is previously determined using a conventional obstetric stethoscope.
And to measure the tone of the uterus, a strain gauge is used (to measure the strength of contractions and spontaneous contractions of the uterus). During contractions, the pressure on the strain gauge increases in proportion to the intrauterine pressure. It is converted by the sensor into an electrical impulse and recorded as a curve on a moving paper tape.
A cardiotocogram is a paper tape (moving at a speed of 1-3 cm/min.) with two curves aligned in time. One of them (upper curve) displays the heart rate (HR), and the other shows uterine activity (uterine contractions).
Previously, during CTG, pregnant women themselves noted the movements of their baby in the stomach by pressing a button on the device. At the same time, a mark appeared on the graph, allowing one to compare the change in the fetal heart rate and its motor activity. The latest models of cardiac monitors are equipped with sensors that continuously record the intensity and duration of fetal movements.
Monitoring the condition of the fetus is an important goal of examining a pregnant woman. It can be carried out different methods. Cardiotocography is the most common, painless and accessible method of instrumental monitoring of the condition.
Cardiotocography is a technique for assessing the condition of a fetus developing in the womb, which consists of analyzing changes in its heart rate at rest, during movements, and also in response to external factors.
Equipment for this study - cardiotocographs - are available in all antenatal clinics and maternity hospitals.
The methodology of this study is based on the well-known Doppler effect. The hardware sensor creates special ultrasonic waves that are directed into the body and reflected from the surface of media with different sound conductivity, after which they are recorded again by it. When the interface between media shifts, for example, when moving, the frequency of the created and received ultrasonic wave becomes different. The time interval between each contraction of the heart is the heart rate (HR).
The purpose of CTG is to timely identify deviations in the functional state of the fetus, which allows the doctor, if any, to select the necessary therapy, as well as to choose the appropriate timing and method of delivery.
Preparation
No special preparation is needed for this study.. But to receive reliable results During the examination, the woman should be relaxed and in comfortable position, don't move. Therefore, before the procedure, you should go to the toilet in advance.
It is recommended to eat approximately 2 hours before the test and should not be done on an empty stomach. In agreement with the doctor, small snacks with something sweet are allowed during the procedure if the baby is in the sleep phase in order to activate it. To add to this, you can purchase sweet foods in advance.
You should not take painkillers and sedatives 10-12 hours before the examination.
Methodology
During the examination, the expectant mother takes a position on the couch, lying on the right or left side of the body or half-sitting, leaning on a pillow. Special meters are fixed on her stomach - gel is applied to one and fixed in the place where the fetal heartbeat is best felt, the other sensor, which registers excitations and contractions, is placed in the area of the projection of the right angle or the fundus of the uterus. The patient independently notes the periods of fetal movement using a button to register fetal movements.
Monitoring is carried out for at least half an hour to obtain the most accurate information about well-being. This duration of the study is explained by the child’s frequent alternation of sleep and wakefulness phases.
Decoding
Unlike many other research methods, decoding CTG at 32, 33, 34, 36, 37, 38, 39 and 40 weeks does not have any significant age-related nuances. There is a slight trend towards a decrease in the average fetal heart rate from 32, 33, 34 to 38 weeks.
Fetal movements on a cardiotocogram
One of the components of CTG recording is currently actography - recording fetal movements in the form of a graph. There are two ways to assess a child's movements. The mother can independently count the movements of the fetus that she feels. Or many modern devices are capable of recording movements themselves using a sensor. The second registration method is considered more reliable. In this case, the movements appear on the actography graph as high peaks.
The fetus moves almost constantly, except during periods of sleep. According to CTG data, it is normal for 32.34, as well as 35-40 weeks developing pregnancy the motor activity of the fetus generally increases. At 34 weeks, there is an average of 50-70 movements per hour. After 34 weeks, an increase in the number of movements is recorded. Thus, from 60 to 80 movements per hour are recorded. The average duration of episodes of movements is 3-4 seconds. Gradually, as the fetus grows, it becomes more crowded in the uterine cavity, so closer to it it becomes calmer.
Contractions on a cardiotocogram
In addition to the fetal heart rate and its movements, CTG can record contractile movements of the uterus, that is, contractions. The recording of contractions on CTG is called a tocogram and is also depicted as a graph. Normally, the uterus reacts to the movements of the fetus in it with its contractions (contractions). At the same time, a decrease in the child’s heart rate is recorded on CTG in response to uterine spasms. Contractions are the main sign of impending labor. Based on the tocogram, the doctor can determine the force of contraction of the muscular layer of the uterus and distinguish false contractions from the true ones.
Based on all of the above, it is clear that CTG is a very important examination of the condition developing fetus in the womb, which allows you to obtain information about the state of the heart rhythm, movements and even evaluate contractions. Any abnormalities on CTG require a thorough cumulative analysis by a competent specialist to be accepted necessary measures that can save lives little man. All these properties make CTG an indispensable type of examination.
Cardiotocography (abbreviated CTG) makes it possible to assess the condition of the baby, its cardiac activity and the development of pregnancy in general.
According to the examination plan for pregnant women, cardiotocography is prescribed weekly starting from the 32nd week. The last diagnostic procedure can be performed in the maternity hospital.
What is fetal CTG, how and why is it performed?
Cardiotocography– a diagnostic procedure during which the baby’s heartbeat, motor activity and contractions of the uterine muscles are continuously recorded.
Purpose of the procedure– identification of signs of hypoxia, fetal anemia, abnormalities in the functioning of the heart (including congenital anomalies). CTG also helps diagnose oligohydramnios and fetoplacental insufficiency.
Modern CTG equipment is equipped with sensors to assess the condition of two babies at once. This is true if a woman is pregnant with twins.
The first planned cardiotocography is prescribed at 32 weeks, since by this time the fetus’s cardio-contractile reflex is already quite well formed. Only from this period is the relationship between the child’s activity and his heart rate clearly visible.
Cardiotocography can be prescribed for more early stages, pathological rhythms are clearly recognized from the 20th week of pregnancy.
CTG procedure: how is it performed?
Cardiotocography is carried out using special equipment, which includes two sensors connected to a device for recording data. The first sensor records the baby's heartbeat, and the second - the contractions of the uterine muscles.
So, first, the doctor places a stethoscope on the abdomen - a tube with a flared end, with the help of which the child’s heart is listened to during each visit to the obstetrician-gynecologist.
This is how the best place to listen to the baby’s heartbeat is determined. Next, an ultrasonic sensor is placed on this area and secured around the body with a belt. This sensor will record the fetal heart activity.
The second sensor (strain gauge) is also fastened with a belt to the stomach, but in the area of the fundus of the uterus (above the navel, approximately under the ribs).
A gel is used to remove the air layer between the sensor and the skin of the abdomen, which interferes with data reception. It is absolutely safe for the baby and mother.
Also, the expectant mother is given a remote control, which is equipped with a button. The woman should press it every time she feels the baby moving. This will allow you to evaluate changes in the fetal heart rate during the period of its activity.
Cardiotocography most often lasts 40, 60 or 90 minutes. But some LCD procedures are carried out in 20-30 minutes, and in the maternity hospital at the beginning labor activity CTG takes about 10-15 minutes. This is enough to draw conclusions about the condition of the fetus based on the obtained cardiogram.
Preparing for CTG
No preparation is required for cardiotocography. But in order for the indicators to be objective, during the procedure the woman must take the most comfortable position.
Usually, the expectant mother is asked to sit, leaning back on the back of a chair or lie half-sided (i.e., you need to lie on your back and slightly turn on your left side, and place a bolster or pillow under your right).
Cardiotocography should not be performed “lying on your back”!
This way the inferior vena cava will not be compressed, as a result of which conclusions about the condition of the fetus will be as reliable as possible.
There is no guarantee that the child will be awake during the CTG. Therefore, it is recommended that a woman eat a piece of chocolate 10-15 minutes before the procedure (you can eat it during the procedure), so the baby will begin to be active.
Also, 8-12 hours before the procedure, you should not take No-shpa (antispasmodics), sedatives, painkillers and other drugs that may affect the result of cardiotocography.
And on top of everything else, the woman must be healthy at the time of the procedure, since acute respiratory infections/ARVI and other infectious and inflammatory diseases can cause fetal hypoxia. In this case, the CTG will need to be retaken after recovery.
With low hemoglobin, the fetus may show signs of hypoxia!
Cost of CTG
In budgetary Russian institutions the procedure is free. In private clinics, the cost consists of several factors: the quality of equipment and service, and the level of the institution. In private clinics in Russia, the price range is about 800-1200 rubles for one cardiotocography procedure.
Is CTG dangerous for the fetus?
Cardiotocography has no contraindications. This procedure is 100% safe for both the baby and the mother. It is completely painless and even pleasant, since the woman has the opportunity to listen to her baby’s heartbeat for almost an hour.
Cardiotocography during pregnancy is prescribed once a week, but it can be done at least every day. This informative method allows you to timely determine whether something threatens the fetus. If indicators deviate from the norm, prescribe additional methods diagnostics, as well as preventive and therapeutic measures.
Interpretation of CTG results + norm of all indicators
The result of CTG is curves printed on paper tape. After deciphering them, the doctor determines whether there are deviations from the norm.
Cardiotocography evaluates indicators such as:
- basal rhythm (basal heart rate)– the number of contractions of the baby’s heart per minute.
The device itself determines the fetal heart rate according to the read data. If there are disturbances in the functioning of the heart, the heart rate may be calculated incorrectly (halved or vice versa).
It is important to know!
If in a normal state the norm is a heart rate equal to 120-160 beats/min., then during physical activity, and also when pelvic location For the fetus, the normative heart rate value is much higher – 180–190 beats/min.
During a post-term pregnancy, it is considered normal if the lower limit of the basal heart rate is in the range of 100-120 beats/min.
During the rest period, the baby’s heart rate (with cephalic presentation) should be in the range of 120-160 beats/min.
If the heart rate is more than 160 beats/min, then this indicates that the baby is developing tachycardia:
- moderate – with a basal heart rate from 160 to 180 beats/min;
- pronounced – with BHR over 180 beats/min.
Tachycardia can be observed with: mild degree fetal hypoxia, anemia in the child, inflammation and infection of the amnion (amnionitis), excessive production of hormones thyroid gland in the expectant mother (hyperthyroidism).
When heart rate is more than 200 beats/min. and the absence of basal rhythm variability, the child is diagnosed with supraventricular tachycardia, which can lead to the development of heart failure.
If the fetal heart rate is less than 120 beats/min., then this indicates bradycardia:
- moderate – with a basal heart rate of 100-120 beats/min;
- pronounced – with BHR less than 100 beats/min.
The cause of bradycardia may be moderate or significant fetal hypoxia, severe anemia, or the presence of congenital heart disease.
As a rule, when the heart rate is less than 100 beats/min. and virtually no rhythm variability, emergency delivery is performed. In this condition, the risk of intrauterine death of the child is very high.
A sinusoidal type of heart rhythm is also a pathological basal rhythm (see graph 1), when the cardiogram looks like a wavy line (without sharp teeth). This basal rhythm is due to the development of anemia in the fetus, the presence of severe hypoxia, or the course of an immunoconflict pregnancy.
Chart 1 – Sinusoidal basal rhythm
If the heart rate is sinusoidal and oxygen deficiency in the fetus is confirmed, the issue of emergency delivery is decided in order to save the baby’s life.
- heart rate variability characterized amplitude(the difference between the largest and smallest number of heart rates) and oscillation frequency(number of oscillations in 1 minute).
Heart rate range has no such diagnostic value. It can reach 50 and even 90 beats/min, which is quite acceptable.
Normally, the amplitude should be in the range from 6 to 25 beats per minute, and the frequency - from 7 to 12 times per minute.
An increase in the number of oscillation amplitudes (over 25 beats/min) is called in medicine “saltatory rhythm” (constantly jumping teeth, often with an increasing character, see graph 2).
Saltatory heart rhythm is observed with moderate fetal hypoxia, entanglement of the umbilical cord around the neck/torso or with compression of the umbilical cord (compression of the umbilical cord, for example, when it is located between the baby’s head and the mother’s pelvic bones).
Graph 2 - Saltatory fetal heart rate
Decrease in oscillation amplitude to less than 6 beats/min. called “monotonous rhythm” (see graph 3, it does not have sharp, high teeth).
A monotonous heart rhythm is observed with fetal hypoxia and acidosis, cardiac development defects, tachycardia, or if the fetus is only sleeping at the time of diagnosis. Also, if a pregnant woman took a sedative shortly before the procedure, then this may affect the decrease in the child’s heart rate variability.
Graph 3 - Monotonous fetal heart rate
The absence of rhythm variability (0-1 beats/min) is called a “silent rhythm” (see graph 4).
A silent rhythm occurs with severe fetal hypoxia, severe damage to its central nervous system, incompatible with life malformations of the fetal heart.
Graph 4 – “Mute” or “zero” heart rate
- acceleration (increased heart rate). At external influence(palpation of the fetus during a vaginal examination), when the baby contracts or moves, his cardio-contractile reflex is triggered, and his heartbeat quickens.
Normally, the heart rate should be accompanied by accelerations, with a frequency of 2 or more accelerations per 10 minutes. On the graph, accelerations are displayed in the form of tall teeth (they are marked with check marks in the example).
Graph 2 – Example of a normal fetal CTG
Let's calculate (using an example) how many accelerations there were during each 10 minutes: in the first 10 minutes there were 4 accelerations, in the second 10 minutes there were also 4 accelerations. Total 8 accelerations.
- deceleration (slowing heart rate)- these are the reactions of the child’s body to compression of his head during contraction of the uterus.
Normally, decelerations should be absent. It is permissible to have only fast (early) decelerations which occur during uterine contractions. Slight early decelerations are not an adverse event.
On the cardiogram, decelerations look like large depressions (in graph 2 they are indicated by crosses).
While some devices themselves mark accelerations, the devices do not mark decelerations.
Slow (late) decelerations, which occur within 30-60 seconds after the next uterine contraction, indicate fetal hypoxia and fetoplacental insufficiency, and long-term ones indicate premature detachment placenta and other complications of pregnancy.
According to the maximum amplitude of slow decelerations, the following degrees of severity of hypoxia are distinguished:
- light – with an amplitude of no more than 30 beats/min.;
- moderate – with an amplitude from 30 to 45 beats/min.;
- heavy – with an amplitude of more than 45 beats/min.
Fetal movements. The baby’s physical activity is also recorded, which the pregnant woman reports to the computer using a button. 1 hour of research must be recorded at least 10 fetal movements.
The presence of hiccup-like movements with a normal cardiogram does not indicate oxygen starvation of the fetus.
Breathing movements. Their frequency must be more than 1 time and last at least 30 seconds.
Fetal condition indicator is a computer assessment of the baby’s condition, which is automatically provided by the device based on the results of cardiotocography.
The assessment of the fetal condition is calculated mathematically using the data obtained. The accuracy of such an assessment is 90%, while the accuracy of a visual assessment of the cardiogram results by a doctor is only 68%.
Here is a breakdown of the fetal condition indicators, which are within the following limits:
- 0-1.0 – healthy fetus;
- 1.1-2.0 – initial disturbances in the condition of the fetus;
- 2.1-3.0 – severe disturbances in the condition of the fetus;
- 3.1-4.0 – pronounced disturbances in the condition of the fetus.
Sleep adjustment is also calculated automatically and is necessary to obtain a more accurate final CTG result. By taking this indicator into account, the accuracy of diagnosing the fetal health status increases.
The line “adjustment for sleep” indicates the period of time when the fetus was sleeping, for example, 0 – 30 = 30. This means that from the beginning of the recording until the 30th minute, the fetal heartbeat was calm, the baby was sleeping at that time. And diagnostics must be carried out only during the baby’s waking hours.
The woman is asked to change her body position or eat some chocolate.
This is all the information regarding the first graph on the tape - the fetal cardiogram. The second graph is tocogram. She reflects contractile activity uterus (or uterine SA), which should not exceed 15% of the baby’s heart rate, and should not last more than 30 seconds.
The final assessment of the fetal condition is given on a 10-point (according to Fischer) or 12-point (according to Krebs) scale.
- up to 4 points. The child suffers from severe hypoxia. Emergency delivery is required.
- 5-7 points. There is no life-threatening oxygen starvation fetus It is advisable to conduct additional studies of his condition or repeat CTG in a day or two.
- 8-10 points according to Fisher or 9-12 according to Krebs. Good fetal condition.
Deviations from the norm cannot be the basis for making a 100% diagnosis, since CTG provides information about the baby’s condition only during a certain period of time. To confirm or refute a particular ailment, repeated procedures of cardiotocography, Dopplerography and ultrasound are prescribed.
ABOUT bad results KTG says:
- basal rate less than 100 or more than 190 beats per minute;
- rhythm variability less than 4 beats per minute;
- lack of accelerations;
- presence of slow decelerations.
If the results of cardiotocography are very poor, the doctor refers the pregnant woman to C-section or induces labor artificially. During such a delivery, CTG can be performed more than once. In such a situation, this procedure allows you to determine whether there is a risk to the baby’s health.
It also happens that a child experiences oxygen starvation, but he has already adapted to this condition. Therefore, CTG will not show any deviations from the norms.
Normal fetal cardiotocogram. What is she like?
CTG is considered normal if:
- basal rate not lower than 120 (acceptable 110) and not higher than 160 beats/min.;
- high variability is indicated in minutes, there should not be low variability;
- number of accelerations – every 10 minutes diagnostic procedure there must be at least 2 accelerations (provided that there are noticeable contractions during these 10 minutes);
- the number of rapid decelerations – their presence is acceptable, but ideally there should be none at all;
- number of slow decelerations – 0 (normally they should be absent);
- maximum amplitude of slow decelerations – 0 beats/min.;
- number of fetal movements – at least 5 per half hour;
- fetal condition indicator (FSI) – from 0 to 1.05;
- The Dawes/Redman criteria must be met, other indicators are not important.
The main thing in computer cardiotocography is an indicator of the condition of the fetus. It is he who characterizes the condition of the fetus based on the data obtained.
There are some methods ultrasound diagnostics fetal conditions in expectant mothers, which are considered absolutely harmless to the baby. One such method is cardiotocography ( CTG) during pregnancy, normal or deviation from it according to individual indicators of this diagnostic method can be detected on various scales. Based on the results obtained, the issue of the condition of the fetus can be considered and pregnancy management can be adjusted if necessary.
CTG is not a mandatory procedure, so the doctor may not refer you at all. expectant mother for this study, however, if any concerns arise, the procedure must be carried out several times.
Features of the CTG procedure
This diagnostic method is used in the third trimester of pregnancy, usually from 32 weeks. Some doctors prescribe this test at 28 weeks, but the criteria for diagnosis are considered reliable from 32 weeks, since by this time the fetus’s activity-rest cycle has stabilized.
Fetal CTG is used to assess the condition of the unborn child during natural physical activity. If the baby does not show any signs of symptoms or is sleeping at all, most likely the procedure will be rescheduled or performed again - there is nothing threatening in this. Since the method is absolutely harmless to the child, it can be performed an infinite number of times.
If we consider the question in what cases or when to do CTG during pregnancy, then this usually occurs in the following conditions:
- pathology of the placenta detected on ultrasound,
- suspicion of fetal growth retardation,
- opportunity ,
- decreased fetal activity,
- related chronic diseases in a pregnant woman,
- or ,
- abnormalities in the previous CTG,
- fetal entanglement detected on ultrasound.
There is no special preparation before the procedure. However, every woman wants to be prepared for what awaits her. If appointed CTG during pregnancy, how to prepare to her, he will tell everyone common sense. Since the study takes about 40-60 minutes, you should prepare yourself for a long time: take a light snack (apple, bread, chocolate), a blanket and a pillow for comfort. Be sure to go to the toilet before the procedure, otherwise you will have to endure it for a long time, and the results will be unreliable.
The expectant mother will be placed on a couch or in a comfortable chair (you need to be in a reclining state or lying on your side, you cannot lie on your back), a sensor will be attached to your stomach, the information from which will go to the electronic unit. The doctor receives and studies all the data that is reflected on the curve. After the examination, the doctor writes a conclusion, which is given to the pregnant woman.
Fetal CTG results: interpretation
The most important issue this method remains interpretation of fetal CTG. There are several scales, the most popular are the 10-point Fisher scale and the 12-point Krebs scale. Typically, indicators are assessed on both scales and two ratings are written in the conclusion. It is worth considering that the data should not diverge on different scales by more than three points.
Below we will dwell in more detail on the Fisher scale. After CTG interpretation of results goes according to the following parameters, which are individually scored from 0 to 2 points:
1. Basal rhythm (the average between the values of the fetal heartbeat, which does not change for 10 minutes or longer):
- less than 100 or more than 180 beats per minute – 0 points,
- from 100 to 119 beats per minute and from 161 to 180 beats per minute – 1 point,
- from 120 to 160 beats per minute – 2 points.
2. Variability (amplitude):
- less than 3 beats per minute – 0 points,
- from 3 to 5 beats per minute – 1 point,
- from 6 to 25 beats per minute – 2 points.
3. Variability (frequency per minute):
- less than 3 – 0 points,
- from 3 to 5 – 1 point,
- more than 6 – 2 points.
4. Acceleration (an increase in the fetal heart rate by 15-20 beats per minute relative to the base rate, occurring in response to fetal movement, umbilical cord compression, uterine contraction) in 30 minutes:
- 0 (absence) – 0 points,
- 1-4 (periodic) – 1 point,
- from 5 and above (sporadic) – 2 points.
5. Decelerations (decrease in heart rate in response to movement or contraction of the uterus) in 30 minutes:
- severe atypical decelerations – 0 points,
- mild to moderate decelerations – 1 point,
- absence or short shallow decelerations – 2 points.
To avoid subjectivity when interpreting fetal CTG data, modern world medicine are trying to create devices and computer programs, which automate the decryption process as much as possible.
IN normal CTG during pregnancy, the Fisher scale ranges from 8 to 10 points. A result of 6-7 points is considered pre-pathological, and doctors will most likely order a re-examination. If CTG results less than 6 points, this most likely means intrauterine hypoxia fetus and requires immediate hospitalization or emergency delivery.
Fetal health indicator (FSI)
Based on the results of the graph obtained from CTG, doctors find the value of PSP (indicators of fetal condition), which normal development is less than 1. If these values are in the range from 1 to 2, this may indicate the onset of abnormalities in the fetus. If the PSP value is greater than 3, this indicates a critical condition of the fetus. However, no decisions are made based on these data alone; the entire history of the pregnancy is considered. The reasons for deviations in indicators can be not only problems in the development of the fetus (heart failure, anemia, hypoxia), but also some conditions in the expectant mother and child that are not associated with disorders ( elevated temperature in a pregnant woman, sleep phase in a child).
It is worth noting that the CTG method is auxiliary or additional, therefore its results are relied upon only in conjunction with other diagnostic data. This mainly affects small deviations from the norm, so there is no need to sound the alarm if results are diagnosed that differ from the norm before talking and discussing the results with a gynecologist.
Pregnancy is an unusually joyful time for every woman who is preparing to meet her baby. But, in addition, pregnancy is also a very important period, because any mother wants the baby to live “comfortably” in her tummy, without experiencing any inconvenience or lack, so that he develops and is formed according to all indications. In order to monitor how comfortable the baby is in the womb, in order to promptly identify and correct any “problems” in this regard, the pregnant woman has to undergo certain examinations, if necessary. Doctors call CTG one of the most valuable examination methods during pregnancy, which allows for a comprehensive assessment of the condition of the fetus.
CTG (cardiotocography) during pregnancy is carried out in order to obtain results regarding the child’s cardiac activity and heart rate, as well as its motor activity, the frequency of uterine contractions and the baby’s reaction to these contractions. CTG during pregnancy, together with doppleometry and ultrasound, makes it possible to timely determine certain deviations in normal course pregnancy, study the contractile activity of the uterus and the reaction of the baby’s cardiovascular system to them. With the help of CTG during pregnancy, you can confirm (or refute) the presence (or absence) of conditions dangerous to the mother and baby, such as; intrauterine infection, low or polyhydramnios; fetoplacental insufficiency; abnormalities in the development of the fetal cardiovascular system; premature ripening placenta or threat. If suspicions of one or another abnormality are confirmed, this allows the doctor to promptly determine the need for therapeutic measures and adjust the management tactics of the pregnant woman.
When is CTG done during pregnancy?
To conduct CTG during pregnancy, a special device is used, which consists of two sensors connected to a recording device. Thus, one of the sensors takes readings of the fetal cardiac activity, while the second records uterine activity, as well as the baby’s reaction to uterine contractions. Ultrasound sensor to listen to the fetal heartbeat and strain gauge to record uterine contractions are attached to the pregnant woman’s belly using special belts. One of the main conditions for the most effective recording of readings is considered to be a comfortable position for the woman during CTG during pregnancy. Thus, readings are taken when the pregnant woman is lying on her back, on her side or sitting; in any case, it is necessary to choose the most comfortable position. In this case, the pregnant woman will hold a special remote control with a button in her hands, which she presses when the baby moves, which makes it possible to record changes in heart rate while the fetus moves.
The most appropriate time to perform cardiotocography is the third trimester of pregnancy, starting from 32 weeks. In addition to the fact that at this moment the fetal cardio-contractile reflex is already formed and the relationship between cardiac activity and physical activity, the establishment of an activity-rest cycle (sleep) also occurs. In principle, CTG can be performed earlier than the specified period, but the reliability of the diagnosis in this case is called into question.
Normal CTG values during pregnancy
CTG indicators during pregnancy cannot be a reason for making a diagnosis; it is just additional information about the condition of the fetus at a given time. Moreover, to form a complete and most plausible conclusion about the vital activity of the fetus, a one-time examination using CTG is not enough: cardiotocography must be carried out several times.
Results for conducting CTG are displayed by a curve on the tape, assessing the readings on which (curves), the specialist can determine whether there is any deviation from the recommended norm. When performing CTG, several indicators are assessed:
- basal rhythm (average heart rate), indicated by the abbreviation BHR or HR. The norm is 110-160 beats per minute in a calm state, 130-190 - with fetal movements;
- rhythm variability (average height of deviations from the basal rhythm). The norm is 5-25 beats per minute;
- deceleration (or deceleration, slowing down the heart rate). They appear on the chart as significant depressions. There are no norms, and if they do occur, they are very short and shallow;
- acceleration (or acceleration, acceleration of heart rate). They appear as teeth on the graph. The norm is 2 or more accelerations per 10 minutes;
- tocogram (uterine activity). The norm is no more than 15% of the frequency of fetal heart contractions of uterine contractions lasting from 30 seconds.
Interpretation of CTG during pregnancy is carried out using a 10-point system, each of the criteria (with regard to variability, the amplitude of deviations and their number is assessed) scores from 0 to 2 points. In the end it turns out complete picture, according to which:
- from 9 to 12 points - the condition of the fetus is normal;
- from 6 to 8 points - the presence of hypoxia, but without high threats, a repeat procedure is required;
- 5 points or less - severe hypoxia, requiring urgent delivery.
If the CTG results are extremely negative, the doctor makes a decision to artificially “force” events - induce labor.
Is CTG harmful to the fetus during pregnancy?
CTG - absolutely safe procedure, which has no contraindications. Because if expectant mother the question is whether CTG is harmful during pregnancy, the answer in this case is always categorical - not harmful. If necessary, examinations can be carried out over a fairly long period of time, even daily. Furthermore- the examination is very, very informative, it allows you to determine in time probable threats pregnancy and fetus, take timely measures necessary actions. But, in any case, the obtained tests should be considered only in the context of the general course of pregnancy and in mutual connection with the results of other examination methods, in particular ultrasound and doppleometry.
Especially for- Tatyana Argamakova
From Guest