Electronic fetal monitoring ("EFM") is a diagnostic tool used to identify a fetus at risk for neurological injury or death, so that timely and appropriate intervention can be carried out before the underlying condition causes irreversible damage. Clinicians use EFM to perform fetal heart rate ("FHR") testing to assess fetal well-being during labor and delivery, when high risk factors exist, or when specific clinical conditions develop before labor and delivery that place the fetus at risk for irreversible brain damage or death.
The goal of FHR monitoring is to detect fetal hypoxia at its earliest stage, and to attempt to prevent asphyxia resulting from prolonged and severe hypoxia. EFM can help to attain this goal because the effects of hypoxia and ischemia on the central nervous system ("CNS") can produce abnormal FHR patterns that can be associated with fetal distress. For FHR testing to have a predictive value, however, the person interpreting the test results should be capable of properly interpreting FHR patterns, recognizing nonreassuring and potentially ominous signs, and intervening before brain damage or fetal death occurs. The sooner that the clinician intervenes, the higher the probability of avoiding irreversible brain damage.
An understanding of the following concepts is critical:
Baseline: The baseline rate is the rate that persists over a given period of time. The interval is typically more than ten minutes. Normal baseline is 120-160 beats per minute ("bpm"). Baseline above 160 bpm is called a Tachycardia. Baseline below 110-120 bpm is called a Bradycardia.
Periodic Changes: Periodic changes are FHR accelerations or decelerations that occur with contractions. Decelerations are routinely described as early, late, or variable.
Early Decels: Early decelerations have a gradual drop in the FHR with the onset of the drop occurring with the onset of a contraction. The U-shape of the early decel mirrors the 1-shape of the contraction. An early decel is not associated with acidosis, but is the result of head compression or parasympathetic stimulation. Early decelerations are not associated with fetal hypoxia, acidosis, or low Apgar scores.
Late Decels: Late decelerations have the same characteristics as early decels, but the onset occurs after the onset of the contraction. Late decelerations are associated with uteroplacental insufficiency. The size and depth of a late decel is not the key, because even subtle late decels can be ominous. As the contraction builds, blood flow through the placenta is diminished, leaving the fetus to rely on reserves. When reserves are inadequate, the FHR decreases and a late decel occurs. After the contraction ends, normal blood flow usually resumes and the FHR recovers.
Variable Decels: Variable decels can occur before, during, or after a contraction, or when no contraction is present (nonperiodic). It is characterized by an abrupt drop in FHR, followed by an abrupt return to baseline. Variable decels can vary in size, timing, depth and duration. Also, atypical variable decelerations can occur, which are more diagnostic of a fetus at risk.
Variable decelerations are associated with cord compression. Thus, the duration of the decel may be tied to the period of time that the cord is compressed. When the umbilical cord is compressed, it causes an increase in fetal blood pressure, reduces oxygen supply to the fetus, and activates responses in the CNS which result in a decrease in FHR and the development of variable decelerations. As hypoxia becomes prolonged, the decelerations may become deeper and last longer.
Variability: The fetal heart rate varies from one beat to the next, because two branches of the CNS control changes in the FHR. The sympathetic division is constantly trying to increase the FHR, while the parasympathetic division is trying to counteract this by slowing the FHR. These beat-to-beat changes are referred to as variability. Normally, the sympathetic and parasympathetic nervous systems have equal opposite effects on the FHR, resulting in a consistent heart rate pattern. When the equilibrium is altered, accelerations and decelerations may occur. Further, the reduction or cessation of oxygen flow to the CNS can lead to a decrease or loss of variability. The connection between hypoxia and the loss of variability enables a physician or nurse who is interpreting a FHR pattern to identify possible signs of fetal distress. Variability is used to predict fetal status at a given point in time. As hypoxia continues and acidosis develops, long-term variability may decrease. Short-term variability may be difficult to determine without using a direct internal scalp electrode.
Nonperiodic Changes: Nonperiodic changes can occur spontaneously, without contraction activity, and they are also described as accelerations or decelerations. For example, variable decelerations can appear during a nonstress test and they may be a sign of cord compression or oligohydramnios, both of which can have adverse effects on the fetus.
Remember!
The knowledge that potential neurologic injury can result from asphyxia must play an important role in shaping the standard of care and the timing of delivery. Since EFM cannot predict the precise moment when asphyxia develops and is capable of producing irreversible brain damage, clinicians should not delay the delivery when FHR patterns indicate that the underlying condition affecting the CNS is getting worse. The obstetrician must be ready to intervene if faced with EFM data that suggests a compromised fetus in distress. Delivery must occur before hypoxia advances to the point where asphyxia results and the baby suffers a CNS injury. In litigation, the EFM strips may provide valuable evidence confirming that the intrauterine environment was becoming increasingly hostile and that the delay in delivery unreasonably increased the risk of death or irreversible brain injury.
Please Note:
This web site is not intended as legal advice on cerebral palsy, and is not a substitute for obtaining guidance from your own legal counsel about cerebral palsy litigation. It provides general educational information about the standards of care and causation issues that can arise in obstetrical malpractice and cerebral palsy litigation. Readers of the articles contained within this web site should not act upon the cerebral palsy information without first consulting with a lawyer who is experienced in evaluating and litigating cerebral palsy and obstetrical malpractice cases. Mr. Apfel is admitted to practice law in Maryland and the District of Columbia. When Mr. Apfel is asked to participate in cerebral palsy
litigation filed in other states, he will associate with, and act as co-counsel with, an attorney licensed in that state who is familiar with the local laws and procedures.
