CTG Flashcards
What two parameters does a CTG monitor?
Fetal heart rate and maternal contractions
Describe the acronym employed to interpret CTGs?
DR C BRAVADO
Define risk Contractions Baseline rate Accelerations Variability Decelerations Overall impression
Define fetal tachycardia and name some causes (5)
HR > 160
Causes:
- fetal hypoxia
- chorioamnionitis
- Fetal/maternal anaemia
- Hyperthyroidism
- Fetal tachyarrythmia
Define fetal bradycardia?
< 100 bpm
In what situations is it common to have a fetal HR between 100 and 120 bpm?
Postdates gestation
Occiput posterior or occiput transverse presentations
Define prolonged severe bradycardia and what this indicates?
Name some causes of prolonged severe bradycardia (5)
HR < 80 for > 3 minutes.
Indicates severe hypoxia.
Causes: cord prolapse cord compression Epidural and spinal anaesthesia Maternal seizures Rapid fetal descent
Variability is an indicator of what?
fetal nervous system, baroreceptors, chemoreceptorsand cardiac responsiveness.
A healthy fetus will be constantly adapting its heart rate in response to changes in its environment.
It indicates an intact neurological system in the fetus.
What is the normal range for HR variability?
5-25bpm
Define non-reassuring and abnormal fetal HF variability?
Non-reassuring:
- less than 5bpm for between 30-50mins
- > 25 bpm for 15-25mins
Abnormal:
- < 5bpms for > 50 mins
- > 25bpm > 25 mins
- sinusoidal
what is the most common cause for reduced fetal variability?
fetal sleeping. Should last for no more than 40 mins.
Name causes for reduced variability?
fetal sleeping (most common cause).
Fetal acidosis, more likely if late decels are present.
Fetal tachycardia.
Drugs: opiates, benzos, methyl-dopa, MgSO4-
Prematurity: variability is reduced at younger gestations.
Congenital heart abnormalities.
Define an acceleration?
An abrupt increase in the fetal HR of greater than 15bpm for > 15 secs.
Are reassuring.
when occur alongside uterine contractions is a sign of a healthy fetus.
What does the absence of accelerations in an otherwise normal CTG indicate?
uncertain significance.
Define a deceleration?
Why do these occur?
An abrupt decrease in fetal HR by > 15bpm for > 15 secs.
Occurs in response to hypoxia. In response to hypoxic stress, the fetus reduces its heart rate to preserve myocardial oxygenation and perfusion.
How are decelerations described?
early, late and variable.
Define early decelerations
Start when uterine contractions begin and recover when uterine contractions stop. This is due to increased fetal intracranial pressure causing increased vagal tone. It therefore quickly resolves once the uterine contraction ends and intracranial pressure reduces. This type of deceleration is, therefore, considered to be physiological and not pathological.
Define a variable deceleration?
Variable decelerations are observed as a rapid fall in baseline fetal heart rate with a variable recovery phase.
Variable in duration and may not have any r/s to uterine contractions.
They are most often seen during labour and in patients’ with reduced amniotic fluid volume.
Describe the normal mechanism of a normal variable decel?
Variable decelerations are usually caused by umbilical cord compression. The mechanism is as follows:1
- The umbilical vein is often occluded first causing an acceleration of the fetal heart rate in response.
- Then the umbilical artery is occluded causing a subsequent rapid deceleration.
- When pressure on the cord is reduced another acceleration occurs and then the baseline rate returns.
What is a reassuring feature of a variabl decel?
The accelerations before and after a variable deceleration are known as the shoulders of deceleration. Their presence indicates the fetus is not yet hypoxic and is adapting to the reduced blood flow. Variable decelerations can sometimes resolve if the mother changes position. The presence of persistent variable decelerations indicates the need for close monitoring.
What is a non-reassuring sign of a variabl decel?
The presence of persistent variable decelerations indicates the need for close monitoring. Variable decelerations without the shoulders are more worrying, as it suggests the fetus is becoming hypoxic.
Define a late decel?
What do late decels indicate?
Late decelerations begin at the peak of the uterine contraction and recover after the contraction ends.
This type of deceleration indicates there is insufficient blood flow to the uterus and placenta. As a result, blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis.
Describe causes of reduced uteroplacental blood flow?
maternal hypoxia
PET
Uterine hyperstimulation
Define a prolonged deceleration?
Define non-reassuring and abnormal
a decel that lasts > 2 mins
Non-reassuring 2-3 mins
> 3 mins = abnormal
Describe the characteristics of a sinusoidal CTG shape?
A sinusoidal CTG pattern has the following characteristics:
A smooth, regular, wave-like pattern Frequency of around 2-5 cycles a minute Stable baseline rate around 120-160bpm No beat to beat variability
What does a sinusoidal CTG indicate?
Severe fetal hypoxia
Severe fetal anaemia
Maternal/fetal haemorrhage.
Overall impression of a CTG is described as (3)
reassuring, non-reassuring/suspicious, abnormal.
What are concerning features for variable decels?
Lasting more than 60 seconds
Reduced baseline variability within the deceleration
Failure to return to baseline
Biphasic (W) shape
No shoulderingDescribe features of variable decels that render them complicated? (
- Rising baseline
- Reduced/reducing variability
- persistent large amplitude (> 60 bpm) and or duration (> 60 secs)
- Slow to return to the baseline after the contraction has ended
- Smooth post-deceleration overshoot
NB: a loss of shouldering that was previously seen may indicate a fetus that is no longer responding appropriately to insults.
What are prolonged decels?
Decels between 90s - 5 minutes
Caused by hypoxia.
Name some causes of prolonged decels? (7)
- Prolonged contractions
- Uterine hyperstimulation
- Supine hypotension
- Post-epidural insertion
- Vaginal examination
- Placental abruption
- Ruptured uterus.
What are late decelerations?
What causes them?
Late decels are generally caused by contractions in the presence of hypoxia. There are no features of a well oxygenated fetus i.e. normal variability, early/variable decels.
- chronic fetal hypoxia (i.e. uteroplacental insufficiency)
- acute fetal hypoxia (i.e. uterine hyperstimulation)
Late decels:
- Uniform in timing relative to contractions
- repetitive in nature
- and will occur with each contraction.
The are contraction dependent (they may differ slightly with each contraction).
They start after the start of the contraction and teh bottom of the decel is usu more than 20 secs after the peak of hte contraction.
They return to the baseline after the contraction has finished.
