First of all, for fetal heart monitoring, we need to clarify the following concepts.
A good graph, in terms of machine setup, we’d better do 3cm of paper walking in 1 minute in horizontal coordinates and 1cm = 30bpm in vertical coordinates. this looks clearer.
Image click to open in a new window to view Li Aoshang, Department of Obstetrics and Gynecology, People’s Hospital of Mianyang City Cai Yan, Department of Obstetrics and Gynecology, Fourth Hospital of Harbin Medical University
Fetal heartbeat: It can be heard with a stethoscope through the abdominal wall of the pregnant woman at 18-20W of gestation. The normal rate is 120 beats/min-160 beats/min, and some books are 110 beats/min-160 beats/min. In the early stages of fetal heart formation, the fetal heart rate tends to be slow, about 65bpm-75bpm, it can reach 125bpm at 8 weeks of gestation and may reach 175bpm at the end of 11 weeks, in the middle and late stages that is now the normal range for monitoring.
Baseline fetal heart rate: the average of fetal heart rate over 10 minutes in the absence of fetal movement and without the effect of contractions.
To clarify the baseline baseline value, the following points should be grasped.
1.When there is no fetal movement.
2.When there is no labor activity.
3.Between contractions.
4.When the fetus is not stimulated.
5.Between acceleration or deceleration.
Fetal movement: In normal pregnancy, pregnant women start to feel fetal movement at 18-20 weeks of pregnancy. At the beginning, fetal movement is intermittent and weak, not easily distinguished from intestinal peristalsis, with the continuation of pregnancy, fetal movement gradually increased. There is a certain pattern. It is more uniform from 8am-12pm, least from 2-3pm and most from 8-11pm. Normally, 30 times-40 times/day, varying widely, each pregnant woman has her own fetal movement pattern.
Fetal movement decreases: less than 10 times tired in 12 hours or decreases more than 50% day by day.
Dramatic fetal movement: a significant increase in fetal movement, if the fetus stops moving afterwards, it indicates fetal malformation and hypoxia, with the risk of death. If the cause of hypoxia is removed, the fetal movement will return to normal.
Fetal heart rate acceleration: temporary increase in fetal heart rate of more than 15 bpm at baseline, lasting for more than 10 seconds. The acceleration usually starts after 25-26 weeks and the acceleration mechanism is perfected after 28-29 weeks. it will be more perfect after 32 weeks. This is the reason why fetal heart monitoring is not done in the early stages.
There are many types of fetal heart decelerations: early decelerations, variable decelerations, late decelerations, prolonged decelerations, terminal decelerations, etc. The concepts of ED, VD and LD are clearly stated in the textbook, so I won’t go into more detail here. The main point is to write about how to identify and the characteristics of each.
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Variable decelerations are graded in two ways: mild to moderately severe and mild to severe.
Mild decelerations: fetal heart rate is 80 beats per minute and the duration of deceleration is less than 30 seconds.
Moderate decelerations: the fetal heart rate is between 70 beats/min and 80 beats/min, and the duration of deceleration is between 30 seconds and 60 seconds.
Severe variant decelerations: fetal heart rate is below 70 beats/min and the duration of deceleration is greater than 60 seconds.
Another fractionation, which combines mild to moderate into mild and leaves severe unchanged. According to Krebs, mild to moderate makes little difference to the fetal prognosis and it is simpler to typify it as mild to severe.
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Significance of early decelerations, variant decelerations, and late decelerations.
I. Early deceleration.
It is generally believed that early decelerations are harmless. It is based on the fact that it occurs mostly in the middle and late stages of the first stage of labor, when the opening of the uterus is 5-7 cm wide and the fetal head enters the pelvis and is caused by pressure. It is the result of a momentary increase in intracranial pressure, a decrease in blood flow to the greater farce, and sympathetic inhibition and parasympathetic excitation. Early decelerations are thus more common in immature infants, in advanced primigravida and in cephalopelvic disproportion. However, early decelerations are sometimes found graphically early in labor and may be caused by umbilical cord factors. Therefore, early decelerations occasionally occur in the middle to late first stage of labor and have no particular clinical significance. If early decelerations occur continuously and get progressively worse, the curve drops more than 50-80bpm or drops below 100bpm, or occur frequently in early labor, cord compression and fetal hypoxia should be considered possible.
Features.
1. Deceleration occurs simultaneously with contractions. The end of contraction and the return of decelerated fetal heart rate to the original baseline level.
2, the time difference between the peak of contraction and the lowest point of fetal heart rate decrease is less than 15 seconds, with an average of 3.5 seconds.
3, often occurs when the opening of the uterus is 5-7 cm and the fetal head is in the process of descending.
4.Changing maternal position or oxygenation, the graph remains unchanged.
5.Injecting atropine can make the deceleration disappear.
6.The amplitude of fetal heart rate deceleration is mostly at 20-30bpm.
II. Late decelerations
The clinical significance of late decelerations should be judged by combining the strength of contractions and the stage of labor progress. If late decelerations occur frequently under normal contractions, especially in the early stage of labor, or in the late stage of labor, but combined with no acceleration for a long time, the baseline rate is too fast or too slow, and the variability disappears, it is a serious manifestation. Late decelerations occur occasionally during labor or appear temporarily when the uterine opening is complete and then improve, then they are mostly uneventful. Especially in the case of acceleration, it can still be considered as a “reassurance figure”.
Characteristics
1. Deceleration often starts after the peak of contraction. At the end of the contraction, the decelerated fetal heart rate is delayed to return to the baseline level and the deceleration lasts longer.
2. The time difference between the peak of contraction and the lowest point of fetal heart rate decrease is usually greater than 30 seconds, with an average of 40 seconds.
3.It can occur in any period of labor.
4.Fetal heart rate is mostly high at baseline and decreases abnormally.
5.The deceleration cannot be disappeared with atropine.
6.Oxygen and changing position may make the deceleration disappear.
Variable deceleration
Variable deceleration due to umbilical cord factors is the most common graph during labor, especially in the second stage of labor. Variable decelerations often occur in cases of tangled umbilical cord, excessive coiling, too short and too little amniotic fluid. It is not significant if it occurs sporadically or close to the time of fetal delivery. Variable decelerations change from the typical pattern of rapid rise and fall to a pattern of slow rebound or near late decelerations, a sign of increased hypoxia.
Features.
1, It can occur at any stage of labor and has no fixed relationship with contractions.
2.Deceleration occurs suddenly and recovery is rapid.
3, Stronger continuous fetal movement can also cause obvious variant deceleration pattern.
4.The typical mild variant decelerations generally have little relationship with fetal prognosis, but the severe variant decelerations or atypical variant decelerations mostly suggest hypoxia.
5.Changing the position can mostly make the deceleration disappear, but oxygen inhalation cannot change the pattern.
The prognosis is good if the variant deceleration has the following conditions.
1.The duration of deceleration does not exceed 30 seconds – 50 seconds.
2.Able to return to the original baseline rate level rapidly after deceleration.
3, Maintain a normal baseline fetal heart rate as well as a normal baseline variability.
Sine graph: On the basis of no fetal movement response, the baseline rate maintains regular oscillation within the normal range, its amplitude variation is usually 5bpm-15bpm, period 2-5cpm, short variation disappears and the baseline is smooth and consistent. It lasts more than 10 minutes and is considered a sign of hypoxia. It may be seen in fetal anemia, fetal nucleated erythrocytosis due to RH factor. It is occasionally seen in cases of hyperemesis and overdue pregnancy.
Prolonged decelerations: decelerations are long, usually more than 60 seconds, and can occur at any time of hypoxia. It can also occur in the absence of contractions, in supine hypotensive syndrome and in the presence of persistent umbilical cord compression.
Characteristics.
Long deceleration time, usually more than 60-90 seconds and less than 10 minutes. Those exceeding 10 minutes are considered low baseline fetal heart rate and cannot be considered prolonged decelerations.
The reasons are the following possibilities.
1, the umbilical cord is compressed, if the umbilical cord is prolapsed, deceleration occurs immediately.
2.Pregnant women with supine hypotension syndrome or hypotension caused by anesthesia, resulting in severe placental blood supply deficiency.
3.The uterus suddenly has too strong contractions, especially due to tonic spasmodic contractions.
4.Vaginal examination or rapid descent of fetal head during labor is caused by strong stimulation of fetal head and excitation of vagus nerve.
If fetal movement and acceleration appear afterwards, it proves that the fetus is good. If the cause of occurrence cannot be lifted in a short time. The duration of deceleration progressively worsens and the variability decreases, especially when the prolonged deceleration appears as a characteristic of late deceleration with a lengthened tail, it indicates that the fetus is seriously hypoxic and the fetus should be delivered as soon as possible.
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Fetal heart length variation, fetal heart monitoring graphs have fetal sleep cycle variation with cycles of 20min-60min and rarely more than 60min. Therefore, for fetal heart monitoring, if the baseline is smooth, after stimulation of the fetus, it is necessary to monitor again for more than 20 minutes.
When the baseline of fetal heart rate is nearly a straight line, it is a sign of fetal distress when the baseline variation disappears. When a healthy fetus is active, the amplitude variation is 10-25 bpm. When the fetus is in a quiet sleep state, the amplitude variation is smaller, but there is still a general amplitude variation of 6-10 bpm.
The significance of fetal tachycardia.
During pregnancy.
1, Tachycardia in immature infants due to poor vagal dominance.
2, Increased heart rate due to abdominal palpation, which usually does not last for a long time.
3, Maternal infection or other causes of fever.
4. Maternal use of atropine drugs.
5. Mild maternal anemia.
6.Fetal episodes of atrial tachycardia.
7, Maternal tachycardia due to emotional excitement, fetal heart rate increases with maternal increase.
Labor and delivery.
Tachycardia during labor is a sign of fetal distress. After observing whether the body position and blood pressure are normal, it should also be checked for anemia and infection. If tachycardia occurs after rupture of membranes, vaginal examination for cord compression should be performed.
1, Fetal distress.
2, Maternal use of atropine analogues or beta-receptor stimulants.
3, Infection.
4, Acute anemia, such as early placental abruption or rupture of the anterior vessels causing acute fetal anemia.
5, maternal hypotension.
Performance of fetal tachycardia in fetal distress
During labor, the fetal heart rate gradually develops from normal to tachycardia, that is, the fetal heart rate progressively increases, which is the warning signal of fetal distress and the early manifestation of hypoxia.
2.Fetal distress should be considered when the fetal heart rate is tachycardic combined with one of long variant reduction, late deceleration, or variant deceleration (even if it is mild).
3. Fetal distress is also suggested by a fetal heart rate above 180 bpm only.
Fetal heart rate is too slow
Pregnancy.
If 110-120 bpm, there is a normal variation of mild bradycardia, usually without adverse consequences.
If 100 bpm or less, consider the possibility of preeclampsia.
Period of labor.
A mildly reduced fetal heart rate during labor, especially during the second stage of labor, is generally not a dangerous condition as long as no decelerations occur and good variability is maintained. This may be related to mild compression of the fetal head by the birth canal, or the fetal arms retaining the umbilical cord, or the cord wrapping around the extremities.
If severe bradycardia is present, fetal distress is characterized by.
1. fetal distress. 2. maternal use of sympathetic nerve blocking drugs. 3. anesthesia. 4. excessive contractions. 5. prolapsed umbilical cord, wrapped around the neck and too short, compression, etc. 6. maternal hypotension. 7. fetal heart disease. 8. maternal hypothermia. 9. in occipital posterior position, due to severe fetal head parieto-occipital compression, sometimes it also shows significant bradycardia.
Fetal heart rate and fetal distress during labor.
1. A fetal heart rate of less than 120 bpm and gradually decreasing is a precursor of fetal hypoxia and should be taken seriously.
2. A fetal heart rate of 120 bpm or less, combined with reduced variability, or late deceleration, variable deceleration, especially the disappearance of prolonged fetal movement acceleration, is an important feature of fetal distress.
3. A severe fetal heart rate of 100 bpm or less, lasting for more than 3-5 minutes, indicates fetal distress, which is more dangerous and should end the delivery as soon as possible. However, if the labor is progressing smoothly and there is no obvious abnormal graph, but only when the fetal head is exposed, especially when it is already crowned, it is not necessary to be alarmed, it is normal and it is a manifestation of fetal head and umbilical cord pressure.
Many people don’t know where to start when it comes to how to read the chart. I personally recommend the ALSO tutorial method, which is simple, organized and easy to remember.
The English abbreviation is DRCBRAVADO.
DetermineRisk risk determination
Contraction contraction
BaselineRate baseline heart rate
VariabilityVariability
AccelerationsAccelerations
DecelerationsDecelerations
OverallAssessment
Risk analysis: This is a problem that many people overlook. Looking at a fetal heart monitoring graph is not only a matter of the graph alone, but also a comprehensive assessment that takes into account the general condition of the patient. We first need to understand the basic maternal condition, the presence of high-risk factors, first understand the medical history, and then go to the graphs. We first have a basic understanding of the maternal history, determine the risk, and decide on the reserve capacity of the fetus based on the clinical situation. For example, is the fetus full term? Is labor progressing well? Amniotic fluid properties? Does the mother have any underlying disease? Height, weight? etc.
Contractions: Nowadays, all fetal heart monitoring is external monitoring. External monitoring cannot clearly understand the intensity of contractions, but internal monitoring is needed. Therefore, the contractions should be examined and evaluated, and the doctor should feel the intensity, duration and interval of the contractions by hand. To assess the frequency and regularity of contractions, it is possible to use fetal heart monitoring.
The baseline heart rate, variability, acceleration and deceleration would like to see above.
Overall assessment.
The analysis of contractions, fetal heart rate graphs and the risks present allows an overall assessment of the current situation and a decision on management. The terms “fetal distress” and “birth asphyxia” are inaccurate and cannot be used for assessment. The fetal heart rate curve can only be described as “reliable” or “unreliable”, or as fetal acidemia, hypoxia and metabolic acidosis.
If the fetal heart rate is reliable, then a decision needs to be made on how to proceed with fetal monitoring. Intermittent auscultation or continuous monitoring. If the graph of the fetal heart rate is unreliable. It needs to be treated.
1. change the method of monitoring.
2.Evaluate maternal vital signs (temperature, blood pressure, heart rate).
3.Vaginal examination (presence of cord prolapse, vaginal bleeding, rapid descent of the fetal head and cervical dilatation).
4.Stop oxytocin.
5.Acoustic stimulation or cephalic stimulation.
6.Change the maternal position, administer oxygen (6-10L/min) and intravenous rehydration. Glucose can be applied, but not in large amounts for a short period of time, instead it will cause acidosis. Do not exceed 30g/h.
7, if available, scalp blood test.
8, contractions are too strong, apply contraction inhibitors.
9.If the amniotic fluid is too small, amniotic fluid can be infused.
10.Prepare for delivery as soon as possible.
The treatment method depends on the specific situation. The following factors are to be considered.
1. Is the graph improving, stable or worsening? If not corrected, is the situation slowly deteriorating leading to a sudden loss of compensation, or is it suddenly changing as in the case of cord prolapse?
2. What is the fetal reserve function? Is it a full-term baby, a low-risk baby, or are there some risk factors present?
3. Is vaginal assistance possible if the graphic description is decompensated?