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Fetal Surveillance




Nonstress test (NST)

Biophysical profile (BPP)

Vibroacoustic stimulation test (VSAT)

Contraction stress test/ oxytocin challenge

test (CST / OCT)

Fetal kick count

Color Doppler USG

CTG (cardiotocography)

Fetal heart rate (Doppler)

Fetal scalp electrode monitoring

Fetal pulse oximetry

Fetal scalp pH monitoring

Apgar score

Umbilical cord pH

  1. There is a decrease in baseline fetal heart rate of 24 beats/min between 16 weeks and term; or approximately 1 beat/min per week. This normal gradual slowing corresponds to maturation of parasympathetic (vagal) heart control.
  2. Bradycardia: The baseline fetal heart rate lesser than 110 beats/min.
  3. Tachycardia; The baseline fetal heart rate greater than 160 beats/min.
  4. Fetal hypoxia and hypercapnia can modulate the heart rate as it is also under the control of arterial chemoreceptors. More severe and prolonged hypoxia, with a rising blood lactate level and severe metabolic acidemia, induces a prolonged fall of heart rate due to direct effects on the myocardium.
  5. Some causes of fetal bradycardia include congenital heart block and serious fetal compromise (hypoxia/ acidosis).
  6. The most common explanation for fetal tachycardia is maternal fever.
  7. Other causes of fetal tachycardia include fetal compromise, cardiac arrhythmia, and maternal administration of atropine or terbutaline.

Beat-to-Beat Variability

  1. Normal beat to beat variability should be 6-25 beats/minute.
  2. Diminished beat-to-beat variability can be an ominous sign and may indicate a seriously compromised fetus.
  3. Loss of beat-to-beat variability along with decelerations is associated with fetal acidemia.
  4. A common cause of diminished beat-to-beat variability is analgesic drugs given during labor.
  5. A large variety of CNS depressant drugs like narcotics, barbiturates, phenothiazines, tranquilizers, general anesthetics, and magnesium sulfate can cause transient diminished beat-to-beat variability.

Sinusoidal Heart Rate

  1. A true sinusoidal pattern is seen with serious fetal anemia, whether from D-isoimmunization, ruptured vasa previa, fetomaternal hemorrhage, parvo virus infection, or twin-to-twin transfusion. Insignificant sinusoidal patterns have been reported following administration of morphine.
  2. A sinusoidal pattern also has been described with chorioamnionitis, fetal distress (asphyxia), and umbilical cord occlusion.

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