Definition of "CTG"

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CTG (cardiotocography, from "cardio" meaning "heartbeat", "toco" meaning "uterine contractions", and "graphy" meaning "recording" is recording of the fetal heartbeat and uterine contractions during pregnancy, typically only in the 3rd trimester. The machine used to perform the monitoring is called an electronic fetal monitor (EFM, aka cardiotocograph).

  • Non-invasive monitoring (aka CTG), involving 2 transducers placed on the mother's abdomen, one above the fetal heart [to measure the fetal HR], and the other at the fundus [to measure contractions]
  • Invasive fetal monitoring (aka fetal scalp monitor), involving a wired scalp/spiral electrode attached to the fetal scalp through the cervical opening [and thus vagina]. It is more accurate since movement doesn't affect it

Mnemonic Dr C Bravado:

  • DR: Define risk
  • C: Contractions, which is the number of contractions in any 10 minute window. Each big square is 1 minute, and the 10 minute marks may be outlined too. Both the duration and intensity of contractions cannot be assessed for from the CTG, but only by palpation
  • BRa: Baseline rate, which is the average HR of the fetus in a 10 minute window (do not use a wider window), ignoring any accelerations or deceleration, and should be between 110-160bpm. Bradycardia is <110bpm, and tachycardia is >160bpm
  • V: Variability, which is the variation of the baseline fetal HR in any 10-minute window, excluding accelerations and decelerations. It is reassuring if >5bpm, non-reassuring if <5bpm for 40-90min, and abnormal if <5bpm for >90 mins
  • A: Accelerations, which are abrupt increases in the baseline HR of >15bpm for >15 seconds. The presence of accelerations is reassuring, and there should be at least 2 accelerations every 15 mins, especially if they occur alongside uterine contractions. The absence of accelerations however, in an otherwise normal CTG is indeterminate
  • D: Decelerations (aka depressions), which are abrupt decreases in the baseline HR of >15bpm for >15 seconds. There are various types of decelerations. Be careful not to mistake the mother's HR for a deceleration; if this occurs, a fetal scalp monitor may be required. Types of decelerations include:
    • Early deceleration, is a gradual deceleration of FHR associated with a uterine contraction. The trough from the deceleration occurs at the same time as the peak of the contraction. This means that the deceleration recovers at the same time, and therefore DUE TO the contraction. These decelerations occur due to increased fetal ICP caused by compression of the head by uterine contractions. It therefore quickly resolves once the contraction ends, and ICP reduces. It is therefore physiological
    • Variable deceleration, is a sudden decrease in FHR, taking <30 seconds, between the onset and recovery of the deceleration. The recovery is of variable speed. They are variable in duration, and may not have any relationship with contractions. It is most often seen in Pt's with reduced amniotic fluid volume, and usually caused by umbilical cord compression. They sometimes resolve if the mother changes position. Accelerations seen before and after a variable decelerationare known as "shoulders of deceleration". The lack of shouldering is more worrying as it suggests the fetus is hypoxic
    • Late deceleration, is a gradual deceleration of FHR associated with a uterine contraction. The deceleration is delayed in timing, with the trough of the deceleration, occurring after the peak of the contraction. This means the deceleration recovers AFTER the contraction. Late decels occur when there is placental insufficiency (i.e. fall in oxygen level in fetal blood) triggers reflex constriction of blood vessels in nonvital/peripheral areas to divert blood to vital organs. Constriction of peripheral blood vessels causes HTN that stimulates a vagal response to slow HR. Low oxygen howver, can result in fetal hypoxia and acidosis. This can be caused by maternal hypotension, preeclampsia and uterine hyperstimulation → fetal blood sampling for pH is indicated
    • Prolonged deceleration, is a deceleration lasting >2 minutes. It is non-reassuring if >2 minutes, and abnormal if >3 minutes. The deceleration however, is <10 minutes, as by definition, this would be a change in the baseline HR → immediate fetal blood sampling, or emergency C section
  • O: Overall impression, as to whether it is:
    • Reassuring
    • Suspicious
    • Pathological

Source: 2011/05/29/how-to-read-a-ctg/">Geeky Medics | NSW Health

  • CTG reduces the rate of seizures in tthe newborn
  • CTG has no clear benefit in the prevention of cerebral palsy, perinatal death, or other complications of labor
  • CTG is actually more likely to result in instrumental delivery (forceps or vacuum extraction) or C section. CTG is controversial in low-risk pregnancies, with over-reliance increasing misdiagnosis of fetal disterss, and increasing possibly unnecessary C sections
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Definition of CTG | Autoprac

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