What Is Deceleration?
Decelerations are nothing but a temporary drop in the heart rate of the fetus during pregnancy and delivery. This might occur due to a number of factors such as contractions, low blood pressure, increased activity inside the uterus, etc.
Fetal heart rate (FHR) will be monitored throughout the delivery process as it is an essential factor that represents the baby's health. Generally, there are three types of deceleration based on their time of occurrence. They are:
1. Early deceleration.
2. Late deceleration.
3. Variable deceleration.
Early deceleration happens mostly before the peak of the contraction and is usually harmless. This happens in the later stage of labor when the baby's head is compressed as it passes through the birth canal. This type of deceleration might also happen during the early stage of labor if the baby is in a breech position or if the baby is premature.
Late deceleration does not happen until the peak of contractions has occurred. It begins only after the uterine contractions have been completed. This deceleration in the fetal heart rate is smooth and has shallow dips that are almost similar to the shape of the contraction that caused it. In some cases, this late deceleration does not concern as long as the baby's heart rate begins to gradually improve (accelerate) and return to the normal range.
But in some cases, this late deceleration might signify the baby is not receiving a sufficient level of oxygen. If late deceleration is accompanied by tachycardia (fast heart rate), then the uterine contractions are harming the baby inside and restricting the baby's oxygen supply. Hence in these scenarios, your doctor will prepare for immediate intervention.
Variable decelerations are random, irregular dips and drops in the fetal heart rate and might look more dramatic than late deceleration. The main cause for variable deceleration is when the umbilical cord gets compressed temporarily. This is common in many deliveries as the baby depends on the umbilical cord for its oxygen supply and compression of the umbilical cord is widely common. But if this variable deceleration keeps happening over and over due to repeated compression of the umbilical cord, then it might lead to serious harmful effects on the baby.
If this variable deceleration occurs in the early stages of delivery, then it might lead to some concerns, and hence the doctor might decide to perform a cesarean, but if it happens around the time of delivery and is accompanied by accelerations, then the doctors might consider it to be normal and proceed with normal delivery.
What Are the Causes of Late Decelerations?
The most common and important cause for deceleration is uterine contraction. This might be during different stages and at different intensities throughout the labor process. During contractions, the blood vessels present in the wall of the uterus become compressed, and they reduce the blood flow to the placenta. This, in turn, reduces the oxygen supply to the fetus.
Other than uterine contractions, there are also some conditions that are capable of producing late deceleration. They are:
Maternal low blood pressure.
Reduced oxygen supply to the placenta.
Increased activity and stress inside the uterus.
Also, the other common cause of late deceleration includes an overactive uterus. These are caused due to epidural analgesia, which is the process of injecting anesthesia into the spinal epidural space. This is done during delivery to reduce pelvic pain during labor and delivery.
Also, if the late deceleration is accompanied by acceleration and happens during the later stages of labor, then it might be the result of pushing the baby.
What Are Some of the Possible Complications of Late Deceleration?
As mentioned earlier, when the baby is experiencing repeated or prolonged occurrence of late deceleration, then there are some possible complications such as:
a) Cerebral palsy (CP).
b) Neonatal encephalopathy.
c) Increased chance of admission into neonatal intensive care unit.
d) As mentioned earlier, when the baby is experiencing repeated or prolonged late deceleration, it may be born with a low APGAR score (Appearance, Pulse, Grimace, Activity, and Respiration), which may be associated with CP, neonatal encephalopathy, increased chance of admission to NICU (neonatal intensive care unit).
How Is Late Deceleration Treated and Managed?
The fetal heart rate is one of the most important factors that doctors use to assess the health of the baby inside the uterus. Hence if the fetal heart rate becomes irregular or deviates from the regular pattern, then the doctor will initially try to determine the exact underlying cause. Since both the baby and the mother's life might be affected, the doctor should be able to diagnose the condition with clinical acumen and determine whether the problem can be reversed or not.
If the doctor suspects fetal hypoxia, then he will try to determine the time of delivery to prevent any other serious complications after the baby is born. In addition, proper care should be taken to avoid premature birth.
It is also important to evaluate both the baby’s and the mother's heart rate and health conditions. The doctor should consider the factors such as deceleration or acceleration and the degree of variability to address the exact root cause of late deceleration. According to FIGO (Federation of Gynecology and Obstetrics), the chances of fetal hypoxia remain very low if we prevent repeated late deceleration and maintain the normal heart tracing range.
If the doctor identifies that the cause of late deceleration is reversible, then they will conduct some other tests and closely monitor you. In addition, they will take certain steps that help in treating late deceleration and improve the blood oxygen supply for the fetus. Those steps include:
Lying down in the left lateral, knee-chest, or right lateral position. This helps in relieving the compression of the large vena cava vein caused by the pregnant uterus. This helps in increasing the flow of deoxygenated blood throughout the body, including the uterus and the placenta.
The doctor might administer oxygen for late deceleration, but there is no clinical evidence regarding its effectiveness when used in women with adequate oxygen levels.
If the cause is diagnosed to be hypotension due to spinal or epidural analgesia, the doctors might administer fluid at the time of labor. Similarly, this also has no clinical evidence to support its efficiency in women with normal blood pressure.
If the fetal hypoxia is due to pushing, your doctor might ask you to stop pushing to prevent the rapid progression of the hypoxia.
If these above methods show no positive results and if the deceleration reoccurs and lasts more than 20 minutes, then your doctors might suggest immediate delivery. This same decision is suggested even if the tests show any issues with the baby. In these cases, your doctor will prepare for a cesarean, which is the best choice of action.
The process of delivery and labor will be continuously monitored by a team of multidisciplinary health professionals. Hence they will look into various reasons and causes if late deceleration occurs and will act immediately based on their diagnosis. In order to avoid severe brain injury from lack of oxygen, the doctors will revive the fetus and immediately address the source of the problem. If the condition is severe, then immediate delivery is the best option. That being said, when proper treatment and care are given, babies have shown excellent results and turn out to be both physically and mentally fit.
Frequently Asked Questions