Heartbeat is one of the most important indicators by which the doctor determines the condition of the fetus, its health and compliance with developmental standards. Monitoring of heartbeat parameters is carried out throughout pregnancy, as well as during childbirth.
One of the first organs to form in the fetus is the heart. Even in the fourth week of pregnancy, it appears as a hollow tube, and at the end of the fifth it begins to pulsate and a heartbeat appears. By the ninth week, the fetal heart is already four-chambered, like that of any adult (two atria and two ventricles).
Auscultation
This is a physical diagnostic method that has been used for many years. This means listening to the fetal heartbeat. A stethoscope is used to perform auscultation. The instrument is applied to the belly of a pregnant woman lying on the couch.
Heartbeat is detected starting at 20 weeks. As the fetus grows, heart rhythms become clearer. During the examination, the specialist finds the point of best listening to tones. It determines the rhythm and nature of heart contractions. If the tones are clear and clean, everything is fine. Deafness of tones indicates the presence of intrauterine hypoxia.
Auscultation is a simple and accessible method. This is an advantage due to which this method of listening to the fetal heartbeat is used to this day. But it also has a significant drawback: difficulty in localizing sounds.
What is a fetal doppler, how does it work?
Fetal doppler is a portable device for listening to the fetal heartbeat in pregnant women. Its operating principle is based on capturing and converting ultrasonic waves and the Doppler effect (change in sound intensity depending on distance). Professional models can detect the rhythm of heart contractions already from the end of the first month of pregnancy, while home models can listen to it no earlier than 10-12 weeks.
Expectant parents can hear the heartbeat through headphones or a portable speaker. Many models have a USB cable for transferring the recording to a computer, which makes it possible to save it and, if necessary, send it to a doctor. The device itself consists of a miniature wave converter with or without a display to display frequency and a sensor. There are devices that combine a Doppler with a sensor (one functioning part).
The power source for the fetal doppler is a battery for charging from the mains or battery. The kit may contain a gel for ultrasound diagnostics, or it will need to be purchased at medical equipment stores or pharmacies.
Dopplerography
This is a type of ultrasound examination. With its help, the state of the child’s cardiac activity is determined and the patency of the umbilical cord vessels is assessed. This diagnostic method gives significant results. A qualified specialist determines the presence of hypoxia, detects entanglement of the fetus with the umbilical cord and identifies abnormalities in the functioning of the placenta.
No preliminary preparation is required to conduct the study. Most ultrasound machines are equipped with a Doppler function. The procedure is absolutely painless. It lasts 15 minutes. The study is prescribed to women in the third semester of pregnancy.
The accuracy of detecting disorders using Doppler sonography is 70%. The absence of problems in a specific period of time does not exclude the development of complications in later stages.
Types of bradycardia in the fetus
Based on the nature and intensity of the decrease in heart rate in the fetus, the following types of pathology are distinguished:
- Basal – diagnosed when the embryo’s heart rate decreases to less than 120 times per minute; with timely help, harm to the child and the mother herself can be avoided;
- Decelerant - such bradycardia is diagnosed if the fetal heart rate is no more than 72 beats per minute, and the woman is prescribed hospital treatment with bed rest;
- Sinus - with it the fetal pulse decreases to 70-90 beats per minute, this condition is the most dangerous, so the woman requires urgent hospitalization and intensive treatment until birth.
Determining the exact type and cause of bradycardia is of great importance, since it determines how great the danger is for the child and mother, what treatment strategy should be chosen to treat the disease or at least reduce the risks.
Amnioscopy
This is a visual method with which amniotic fluid is examined. It is carried out in several cases: post-term pregnancy, suspected intrauterine death of the child and prolonged labor in which the amniotic sac has not burst.
Amnioscopy is performed at a stage of pregnancy exceeding 36 weeks. During the study, the doctor evaluates the amount and color of amniotic fluid. The presence of foreign impurities is also determined. The results obtained are sent to an obstetrician-gynecologist.
Fetal monitoring using an amnioscope can detect serious abnormalities. To conduct the study, preliminary preparation is required. Amnioscopy is carried out with the consent of the woman, informed about possible complications. The probability of miscarriage or onset of premature labor after the study is 0.5%.
Fetal bradycardia: causes and symptoms
Not every decrease in a person’s pulse is an anomaly or pathology. For example, it is observed during sleep or when the ambient temperature drops - at such moments the body saves energy and metabolism slows down. Also, a similar phenomenon is observed in athletes, and in some people it is present from birth, but does not have the nature of a pathology. In such cases we speak of physiological bradycardia. Its important difference from abnormal is the absence of pathological symptoms.
Abnormal bradycardia is a decrease in heart rate in which various painful conditions of the body occur: dizziness, cold sweating, loss of consciousness, etc. As a rule, they manifest themselves with a strong reduction in the heartbeat. If it is insignificant, then a person may not experience subjective sensations.
To judge the presence of cardiac bradycardia in the fetus, it is necessary to have an idea of the physiological normal heart rate. In an adult it is 60-80 beats per minute, but in an embryo it changes during its development:
- At 3-5 weeks – 75-80;
- At 5-6 weeks – 80-100;
- At 6-7 weeks – 100-120;
- At 7-9 weeks – 140-190;
- At 10-12 weeks – 160-180;
- At 4 months – 140-160;
- By 9 months – 130-140.
The indicated values are not exact, since the physiological norm for each child may vary slightly. Until approximately the 21st day of pregnancy, the embryo’s heartbeat cannot be heard at all - at this stage, its own heart has not yet begun to form, and metabolism is completely ensured by the mother’s bloodstream.
It is possible to unambiguously diagnose pathological bradycardia in the mother and fetus only in the 2nd trimester (after 20 weeks of gestation), since at this stage its own blood supply system as a whole has already formed, so the pulse should stabilize. The doctor makes a diagnosis if during this period the heart rate is less than 110-120 beats per minute.
Bradycardia can be a “maternal” disease or observed only in the fetus. In the first case, the slowing of the heartbeat of the woman herself also affects the condition of the unborn child; in the second, the pathology of the embryo does not affect the health of the mother. The causes of the disease on the mother's side are:
- diseases of the cardiovascular system - atherosclerosis, unstable blood pressure, coronary heart disease, cardiosclerosis, dystrophy or inflammation of the myocardium (heart muscle);
- general diseases of the body - impaired hematopoietic function of the bone marrow, tumors, anemia, infectious pathologies, renal failure, etc.
On the part of the fetus, the following pathologies are the causes of bradycardia:
- maternal anemia, high environmental toxicity, mental stress in women;
- malformations of the fetus’s own cardiovascular system;
- disorders of the mother’s reproductive system - early aging of the placenta, abnormal accumulation of amniotic fluid, etc.;
- Rh conflict - incompatibility of maternal and embryonic blood according to the Rh factor;
- intoxication of the maternal body due to smoking, drinking alcohol or drugs, and certain types of medications.
Symptoms of bradycardia in the mother are typical signs of oxygen starvation - dizziness, weakness, headache, tinnitus, chest pain, low blood pressure, shortness of breath. If the pathology is observed only in the fetus, it will be indicated by a decrease or cessation of its motor activity, as well as convulsions. The peculiarity of the embryonic form of the disease is that it is impossible to identify it based on the condition of the mother - only by directly observing the child himself using modern diagnostic tools.
Pregnancy in patients with bradycardia is characterized by a high risk of fetal hypoxia. Prolonged oxygen starvation can lead to frozen pregnancy, miscarriage or irreversible damage to the body of the unborn child. His brain suffers especially badly from this, since nerve cells are most sensitive to lack of oxygen.
Take the first step
make an appointment with a doctor!
Echocardiography
This is an ultrasound examination of the fetus that pays close attention to the heart. The study is scheduled between 18-28 weeks of pregnancy. Echocardiography is a complex technique that uses one-dimensional ultrasound and Doppler mode. With its help, the structure of the heart and large vessels is determined.
Fetal echocardiography is performed as indicated. These include the presence of diabetes mellitus in a woman, age (over 38 years), and intrauterine growth retardation of the child. Other criteria are also important: the transmission of infectious diseases, alcohol abuse, as well as the birth of children who have heart problems.
Echocardiography is a safe way to study the heart. It does not cause any discomfort. The doctor receives comprehensive information about the functioning of the heart. This method has no significant disadvantages.
Ultrasound
This is a common diagnostic method during pregnancy. Fetal monitoring is carried out using modern equipment. The number of planned ultrasound examinations does not exceed five times. For the first time, a woman comes to a medical facility to determine pregnancy. Subsequent ultrasounds are performed for different purposes:
- 11-13 weeks – fetal development and the condition of the placenta are assessed
- 19-21 weeks – the size of the fetus and the sex of the child are determined, the condition of the amniotic fluid is assessed
- 32-34 weeks – the baby’s weight and the condition of the umbilical cord are determined. The commensurability of the size of the baby’s head and the birth canal is also assessed.
- Ultrasound before childbirth - possible complications are identified
Transabdominal and transvaginal examinations are performed in medical institutions. In the first case, the sensor is placed on the stomach. In the second case, a special device is used, which is inserted inside.
Ultrasound is a painless method of monitoring the fetus. Its advantages include information content, a high level of security, and no need for preliminary preparation. Ultrasound examinations have been used for 40 years. During this time, no adverse effects on fetal development were identified. For this reason, the technique is successfully used in clinics. But development does not stand still. Traditional methods are being replaced by innovative solutions.
Indications for determining heart rate
Doctors cite the following reasons as the basis for diagnosis:
- Confirmation of the fact of pregnancy itself. So already in the 3rd week of pregnancy you can listen to the fetal heartbeat using ultrasound equipment. In the earliest stages, the fetal heartbeat cannot be heard, so the procedure is repeated at intervals of a week.
- Assessment of the general condition, degree of growth and development of the fetus. The stress of the mother herself or her bad habits and workload immediately have a negative effect on the fetal heartbeat. Based on the diagnostic results, the doctor makes a decision on emergency delivery or termination of pregnancy.
- Monitoring the general condition of the child at the time of delivery. It is at the moment of birth that the child experiences the greatest stress. In many such cases, he copes with them on his own. But when the umbilical cord wraps around the fetus or placental abruption, or other extreme situations, the help of doctors is required.
All these points will allow you to comprehensively assess the general condition of the child, its development according to the timing of pregnancy and, as necessary, apply emergency measures.
Electronic fetal monitoring
This is an advanced technique with which serious complications are determined: cerebral palsy, intrauterine death, cardiac dysfunction. Fetal monitoring is carried out as follows: the woman in labor, lying on her back, has belts with sensors placed on her stomach. One device records the fetal heartbeat, and the second - the duration and intensity of uterine contractions. Sensors are connected to the monitor.
In some cases (for example, serious danger to the fetus), an internal examination is used. Its essence is as follows: the electrode is inserted through the cervix and placed on the baby’s head. With such an examination, the doctor receives the exact data necessary to assess the current situation. Internal monitoring is used after rupture of membranes. The cervix should also be dilated (at least 1 cm).
External electronic monitoring lasts about half an hour. Innovative devices are used in clinics. For example, these could be Avalon fetal monitors. This is technological equipment with the best characteristics. It is distinguished by functionality, long service life, and ease of use.
Fetal monitoring is an advanced technology used in medical institutions equipped with the latest technology. Therefore, we need to take a closer look at its features and advantages.
Recommendations for clinical use for obstetricians and gynecologists
Intrapartum fetal heart rate monitoring: terms, description and basic principles of management
This Practice Bulletin was developed by the ACOG Committee on Practice Bulletins in collaboration with George A. Macones, MD. This information is intended for medical practitioners to make decisions when providing obstetric and gynecological care. These recommendations are not binding as the only correct method of treatment or procedure. Their use in practice may be determined by the needs of the individual patient, available resources, and limitations specific to the health care setting or type of clinical practice.
Rice. 1 Fetal monitor Avalon FM20
American College of Obstetricians and Gynecologists (ACOG)
In most recent years for which data are available, approximately 3.4 million fetuses were monitored in the United States (85% of the approximately 4 million live births), making it the most common obstetric procedure. Despite the widespread use of this research method, there is debate about the effectiveness of monitoring the condition of the fetus, the variability of results between different and single researchers, terminology, interpretation systems and control algorithms. Moreover, it is obvious that when using fetal monitoring, the number of deliveries by cesarean section increases compared to vaginal births. The purpose of this document is to review the terminology used to assess fetal heart rate, review evidence on the effectiveness of fetal monitoring, identify the advantages and disadvantages of fetal monitoring, and describe a system for classifying monitoring data.
A combination of factors such as prenatal complications, insufficient blood supply to the uterus, dysfunction of the placenta and complications during childbirth can lead to an unfavorable outcome. Factors such as hypertension, impaired fetal development and premature birth create the preconditions for an unfavorable birth outcome; they are also the cause of a small number of asphyxial injuries. As a result of studies of normal pregnancies with fetal asphyxia, 63% of those studied were not at risk.
The fetal brain controls the heart rate through a combination of impulses from the sympathetic and parasympathetic nervous systems. Therefore, fetal heart rate monitoring can be used to determine the level of oxygen supply to the fetus. In 1980, 45% of pregnant women took part in the study. In 1988 - 62%. In 1992 - 74% and 85% in 2002. Despite the frequent use of fetal monitoring, limitations of this method include poor intra- and inter-observer reliability, uncertain efficacy, and a high false-positive rate.
Fetal heart rate monitoring can be done either invasively or non-invasively. Most monitors use a Doppler device to measure heart rate non-invasively using an automated system for interpreting and counting Doppler signals. Invasive monitoring of fetal heart rate is carried out using special electrodes, which are a spiral-shaped wire that is placed on the fetal skull or other presenting part of the fetus.
Guidance on terminology and interpretation of fetal heart rate monitoring results.
In April 2008, the National Institute of Child Health and Human Development. Eunice Kennedy Schriever, the American College of Obstetricians and Gynecologists and the Society of Maternal-Fetal Medicine organized a conference on automated fetal heart rate monitoring. In 2008, a conference brought together various groups of researchers, both experts and interested individuals, to develop three main objectives:
1) review and update of terminology for the classification of fetal heart rate graphs adopted in previous workshops;
2) evaluate the current classification system for interpreting specific fetal heart rate charts and create recommendations for such systems for use in the United States;
3) creation of recommendations on the main areas of research in the field of monitoring the condition of the fetus.
For a full clinical interpretation of the monitoring results, it is necessary to determine and study uterine contractions, the maximum permissible values and variability of the baseline fetal heart rate curve, the presence of accelerations, periodic or episodic decelerations, as well as changes in these parameters over time. The number of reference conditions and factors used to interpret heart rate in the United States is central to the proposed system of terminology and interpretation. Two of these conditions are the most important. First, the terminology framework was originally developed for the visual assessment of fetal heart rate graphs, but it needs to be compatible with computerized data interpretation systems. Second, the terminology should be suitable not only for intrapartum examinations, but also for prenatal examinations.
Uterine contractions are defined as the number of contractions during 10-minute periods averaged over 30 minutes. Contraction frequency alone is a partial assessment of uterine activity. Other parameters such as contraction duration, intensity, and relaxation time between contractions are also important in clinical practice.
The terminology below is used to describe the activity of the uterus:
- Normal: 5 contractions or less over 10 minutes every 30 minutes.
- Tachycardia: more than 5 contractions within 10 minutes of a 30-minute interval.
Parameters of uterine contraction:
- The terms "hyperstimulation" and "hypercontraction" are not defined and should be excluded from the terminology base.
- Tachycardia is always defined as the presence or absence of deceleration of the corresponding fetal heart rate curve.
- The term "tachycardia" refers to both spontaneous and artificially induced contractions of the uterus. The actions of medical personnel when tachycardia occurs may be different, depending on the type of contraction: spontaneous or stimulated.
Table 1 summarizes the EFM terms and definitions developed in 2008 by the National Institute of Child Health and Human Development Working Group. Deceleration is considered recurrent if it occurs during at least half of the uterine contraction.
Classification of fetal heart rate graphs
Many different systems for interpreting fetal monitoring results are used around the world and in the United States (4–6). Based on a thorough study of existing criteria, it is recommended to use a three-level system to classify fetal heart rate graphs (see table). It is important to understand that fetal heart rate graphs provide information about the current acid-base status of the fetus. The classification of fetal heart rate curves serves to assess the condition of the fetus at a given time; schedules can and will change. Depending on the clinical setting and analysis methods used, fetal heart rate curves may vary between categories.
Category I: Normal fetal heart rate curves. The fetal heart rate graph of category I shows, with a high degree of probability, the normal acid-base state of the fetus at the time of the examination. Category I fetal heart rate graphs can be obtained in a standard manner; no additional steps are required.
Category II: Uncertain fetal heart rate curves. Category II fetal heart rate graphs are not indicators of a violation of the acid-base status of the fetus, and there is still no clear understanding of the classification of such curves as Category I or Category III. Category II fetal heart rate curves should be checked and further monitored and then re-checked, taking into account all clinical conditions. In some cases, when Category II heart rate curves are obtained, it is necessary to perform additional tests to check the condition of the fetus or intrauterine resuscitation measures.
Category III: Abnormal fetal heart rate curves. Category III fetal heart rate charts show the abnormal acid-base status of the fetus at the time of the examination. Category III fetal heart rate curves should be urgently checked. Depending on the clinical setting, actions to correct abnormal fetal heart rate include, but are not limited to, administering supplemental maternal oxygen, changing maternal position, stopping labor, and increasing blood pressure if maternal hypotension occurs. If these methods do not help, then delivery is necessary.
Table 1. Terms and definitions for automated fetal monitoring
| Schedule | Description |
| Base curve |
— Repeated or episodic changes — Periods of significant changes in heart rate — Segments of the curve that differ by more than 25 beats per minute
|
| Fetal heart rate variability |
|
| Acceleration |
|
| Bradycardia at the height of uterine contraction |
|
| Bradycardia at the beginning of uterine contractions |
|
| Bradycardia during umbilical cord contraction |
|
| Long Slowdown |
|
| Sinusoidal rhythm |
|
Three-level fetal heart rate interpretation system
Category I
Category I fetal heart rate curves include all of the following elements:
- Fetal heart rate range: 110 - 160 beats per minute (bpm)
- Fetal heart rate variability: average
- Bradycardia at the height of uterine contraction or during umbilical cord contraction: absent
- Bradycardia at the beginning of uterine contraction: presence or absence
- Accelerations: presence or absence
Category II
Fetal heart rate curves of category II include all graphs of curves that are not included in category I or category II. They represent a significant group that may be encountered in clinical practice. Examples of category II fetal heart rate curves: Initial frequency
- Bradycardia is not accompanied by a lack of change in the baseline curve.
- Tachycardia
Variability in the baseline fetal heart rate curve
- Minimal change to the base curve.
- No change in the base curve is accompanied by periodic slowdowns.
- Noticeable change in the baseline curve.
Acceleration
- Absence of artificially induced heart rate accelerations after fetal stimulation.
Intermittent or episodic slowdowns
- Intermittent bradycardia during umbilical cord contraction is accompanied by minimal or slight change in the baseline curve.
- The period of prolonged deceleration is 2 minutes or longer, but not more than 10 minutes.
- Periodic bradycardia at the height of uterine contraction with a significant change in the baseline curve.
- Bradycardia during umbilical cord contraction is also characterized by other signs, such as a slow return to the baseline curve, "spikes" or "shoulders".
Category III
Category III fetal heart rate curves include:
- No change in the baseline heart rate curve and any of the following:
— Periodic bradycardia at the height of uterine contraction — Periodic bradycardia during umbilical cord contraction — Bradycardia
- Sine curve
Tips for viewing automated fetal heart rate monitoring results
When using a fetal monitor during labor, the nursing staff or doctor should check the readings regularly. If the patient has no complications, then the fetal heart rate curve should be checked approximately once every 30 minutes during the first stage of contractions, and every 25 minutes during the second stage. The appropriate frequency of monitoring for patients with complications (eg, fetal impairment, late-onset toxicosis (preeclampsia)) is every 15 minutes during the first stage of labor and every 5 minutes during the second stage. The medical institution should periodically produce a report that graphic recording of the fetal heart rate was carried out. Fetal heart rate traces, as part of the patient's medical record, should be labeled and available for review as needed. It is advisable to store fetal heart rate curves in digital format in the form of microfilm, without the possibility of re-recording or editing the files.
Clinical conclusions and recommendations
1) How effective is intrapartum automated fetal heart rate monitoring?
The effectiveness of automated fetal monitoring (EFM) during labor is measured by its ability to reduce the risk of complications such as neonatal convulsions, cerebral palsy, or intrapartum fetal death, while reducing the need for obstetric surgery such as vaginal birth or cesarean section. There are no data from randomized clinical trials to compare the benefits of fetal monitoring with other methods of monitoring during labor. Therefore, the benefits of EFM are determined from reports that compare this method with intermittent auscultation.
Based on the results of a meta-analysis combining data from randomized clinical trials aimed at comparing observation methods, the following conclusions were made:
- Fetal monitoring increased the total number of cesarean deliveries (risk ratio [RR], 1.66; 95% confidence interval [CI], 1.30 to 2.13) and cesarean deliveries with abnormal heart rate compared with intermittent auscultation. or acidosis, or both (RR. 2.37; 95% CI, 1.88 - 3.00).
- Use of EFM resulted in an increased risk of using vacuum and forceps during vaginal delivery (RR, 1.16; 95% CI, 1.01 to 1.32).
- EFM did not reduce perinatal death (RR, 0.85; 95% CI, 0.59 to 1.23).
- EFM use was associated with an increased risk of neonatal convulsions (RR, 0.50; 95% CI, 0.31 to 0.80).
- The use of monitoring did not reduce the risk of developing cerebral palsy (RR, 1.74; 95% CI, 0.97 - 3.11).
The expectation that uncertain fetal heart rate curves can predict the development of cerebral palsy is unreasonable. Positive predictive value of indeterminate heart rate curves in determining the presence of cerebral palsy in selected 2,500 g neonates. and more is 0.14%. This means that out of 1,000 fetuses with uncertain heart rate curves, only one or two will have cerebral palsy. The relative number of false positive findings during monitoring to predict the presence of cerebral palsy is extremely high, more than 99%.
Available data, although limited in number, suggest that the use of automated monitoring does not reduce the risk of developing cerebral palsy. Some studies suggest that cerebral palsy does not change over time, despite the widespread use of fetal monitoring. The main explanation for why the prevalence of cerebral palsy has not decreased due to EFM is that 70% of cases occur before the onset of labor; and only 4% of encephalopathy cases can be completely attributed to intrapartum events.
Whereas, the available data do not clearly demonstrate the benefit of observational monitoring (EFM) over intermittent auscultation, even when the EFM technique is used in patients without complications. For technical reasons, it is impossible to provide recommendations here on how often auscultation of the heartbeat should be performed. One prospective study found that auscultation schedule was followed in only 3% of cases. The main reason for the violation of periodic auscultation is the frequency of testing and compliance with all the required conditions for such registration.
The method of intermittent auscultation is not suitable for all pregnant women. Most clinical trials comparing fetal monitoring with intermittent auscultation have excluded participants at high risk for adverse pregnancy outcomes, in which case the relative safety of intermittent auscultation is questionable. When giving birth to women at high risk of complications (for example, potential fetal impairment, late toxicosis and type I diabetes), it is necessary to continuously monitor the patient using a fetal monitor.
There are no comparative data to determine the optimal frequency of intermittent auscultation in the absence of risk factors. The only method is to record and evaluate the fetal heart rate every 15 minutes during the active phase of the first stage of contractions and at least every 5 minutes during the second stage.
2) What is the variability within and between reviewers when assessing the results of intrapartum fetal monitoring?
There is great interobserver and interobserver variability in the interpretation of fetal heart rate curves. For example, when three obstetricians studied 50 cardiotocograms, their opinions coincided only in 22% of cases. Two months later, during a re-examination of the same 50 graphs, doctors interpreted 21% of the curves differently than when they were first assessed. In another study, 5 obstetricians separately interpreted 150 cardiotocograms. Obstetricians identified approximately 29% of cases identically, indicating poor interobserver agreement.
The interpretation of cardiotocograms is most often consistent when normal curves are presented for study. When interpreting curves, a known birth outcome may change the investigator's opinion of the plot. When assessing identical intrapartum curves, the researcher is more inclined to look for signs of fetal hypoxia and criticize the actions of the obstetrician if the birth had an unfavorable outcome. Therefore, repeated interpretation of fetal heart rate curves, especially when the outcome of labor is known, may be unreliable.
3) When should a preterm fetus be monitored?
The decision to monitor such a fetus requires a discussion between the obstetrician, pediatrician, and patient about the likelihood of whether the premature baby will survive or die (depending on gestational age, estimated fetal weight, and other factors), and a decision about the type of delivery must be made. If a patient is undergoing a cesarean section to save a premature baby, continuous monitoring is required rather than periodic listening. The earliest stage of pregnancy at which this procedure can be performed may vary.
Uncertain fetal heart rate curves may appear in up to 60% of women in early labor, with the most common abnormality being slowing and bradycardia, followed by tachycardia and little or no change in the baseline curve. For early births, bradycardia during umbilical cord contraction is more typical (55-70%) than for full-term births (20-30%). If an abnormal heart rate is present, intrauterine resuscitation, additional tests to check the condition of the fetus, and obstetrics in an acceptable manner are required.
4) What medications can affect fetal heart rate?
The fetal heart rate pattern may be affected by medications administered during the intrapartum period. Most often, these changes are temporary, but sometimes they can lead to the need for intervention by an obstetrician.
Epidural analgesia in combination with local anesthetics (eg, lidocaine, bupivacaine) can lead to blockade of the sympathetic nervous system, a decrease in maternal blood pressure, temporary uteroplacental insufficiency and changes in fetal heart rate. Parenteral anesthetics may also affect fetal heart rate. Randomized clinical trials comparing epidural analgesia with 0.25% bupivacaine and intravenous mepiridine showed that waveform variability was reduced and the increase in fetal heart rate was significantly lower with parenteral analgesia than with local analgesia. The degree of deceleration and the number of caesarean sections delivered when obtaining “unsatisfactory” fetal heart rate curves were similar for both groups. A systematic study of randomized and observational clinical trials also found that the rate of caesarean section deliveries resulting in “unsatisfactory” fetal heart rate curves was the same for patients who did and did not receive epidural analgesia during labor.
The question of the effect of joint spinal-epidurial analgesia during labor has aroused interest. In an intention-to-treat analysis, 1,223 parturients were randomly assigned to receive spinal epidural analgesia (10 µg sufentanil injected into the spinal cavity, followed by epidural bupivacaine, followed by fentanyl) or intravenous mepiridine (50 mg on demand, maximum 200 mg). mg per 4 hours) revealed that significantly more cases of bradycardia and emergency cesarean section due to abnormal fetal heart rate were observed in the group selected for spinal epidural anesthesia. However, the birth outcome was not significantly different between the two groups. There are some methodological inaccuracies in this study. Another randomized controlled trial compared the occurrence of abnormal changes in fetal heart rate during labor in women receiving combined spinal epidural anesthesia (n=41) and epidural anesthesia (n=46). In this study, abnormal changes in fetal heart rate were most often observed in the spinal epidural anesthesia group. Additional studies are needed to determine the safety and effectiveness of spinal epidural anesthesia.
Other drugs that affect fetal heart rate have also been studied (see Table 2). It should be noted that the comprehensive inverse analysis showing a decrease in variability due to the use of magnesium sulfate relates only to early pregnancy and not to changes in magnesium sulfur levels. Research results show different effects of magnesium on the fetal heart rate curve. Some studies show no significant effect; others note small changes in the baseline fetal heart rate curve. However, the reported adverse effects on fetal monitoring should be avoided when using magnesium alone.
A transient sinusoidal heart rate pattern occurred in 75% of patients given butorphanol during labor and was not associated with a risk of adverse outcome. When the fetus was exposed to cocaine, there were no characteristic changes in the heart rate curve, despite the fact that frequent uterine contractions occurred without artificial stimulation. As a result of computer analysis of cardiotocograms and a randomized clinical trial comparing the effects of mepiridine and nalbuphine for intrapartum anesthesia, it was found that there was a decrease in the likelihood of two 15-second accelerations within a 20-minute interval. In the prenatal period, the use of morphine leads to a slowdown in the fetal respiratory movements and a decrease in the number of accelerations in its heart rate.
The effect of corticosteroids used to increase fetal lung maturity during early labor on heart rate has been studied (see Table 2). Among twins and only children, betamethasone use temporarily reduced heart rate variability, which returned to baseline after four to seven days. The use of betamethasone may also lead to a decrease in the number of fetal heart rate accelerations. These changes were not associated with obstetric surgery or risk of adverse outcome. The biological mechanism of this phenomenon is not known. Computer analysis of cardiotocograms shows that the use of betamethasone does not affect the variability of fetal heart rate.
5) What indicators of fetal monitoring correspond to the normal acid-base balance of the body?
The presence of increases in heart rate indicates that there is no change in the acid-base state of the fetus. Data regarding the impact of fetal heart rate variability on birth outcomes are sparse. Results from an observational study indicate that small changes in fetal heart rate are inextricably linked to umbilical cord pH levels greater than 7.15. One study showed that during bradycardia at the height of uterine contraction or umbilical cord contraction, the umbilical cord pH will be above 7.00 in 97% of cases, provided that the fetal heart rate curves are characterized by normal variability. In another retrospective study, normal variation in fetal heart rate was observed in most cases with an unfavorable birth outcome. These studies are limited because they do not take into account other parameters of the heart rate curve, such as the presence of accelerations or decelerations. However, in most cases, a normal change in fetal heart rate confirms optimal fetal health and the absence of metabolic acidemia.
