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Y4 - GOSH > Cardiotocography (CTG) Interpretation > Flashcards

Cardiotocography (CTG) Interpretation Flashcards

1
Q

How is fetal monitoring achieved in low risk pregnancies?

A
  • intermittent auscultation to listen to the fetal heart
  • this is acheived through Doppler
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2
Q

How is fetal monitoring acheived in high risk pregnancies?

A

continuous monitoring with CTG

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3
Q

What features may make a pregnancy become “high risk” and require CTG monitoring?

A
  • intrauterine growth restriction (IUGR)
  • multiple pregnancy
  • meconium stained liquor
  • oxytocin infusion
  • abnormality on intermittent auscultation

meconium staining can be normal post 40 weeks gestation but is a sign of distress prior to this

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4
Q

What is measured on CTG?

A
  • fetal heart rate
  • contractions of the uterus
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5
Q

What are arrows A-D pointing at?

A

A - fetal heart rate in bpm

B - fetal movements (mother presses button when she feels movement)

C - fetal movements (detected by the computer)

D - uterine contractions

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6
Q

What is a fetal scalp electrode?

A

an instrument that screws into the scalp to monitor the fetal HR

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7
Q

When is a fetal scalp electrode used?

A
  • obesity
  • twins
  • abdominal scarring
  • poor quality trace with abdominal transducer

it should be AVOIDED in blood-borne viruses / haemophilia

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8
Q

What are the indications for continuous CTG monitoring in labour?

A
  • sepsis
  • maternal tachycardia (>120)
  • significant meconium
  • pre-eclampsia
  • fresh antepartum haemorrhage
  • delay in labour
  • oxytocin use
  • disproportionate maternal pain
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9
Q

What are the 5 components of the CTG?

A

contractions:

  • the number of uterine contractions per 10 mins

baseline rate:

  • baseline fetal HR

variability:

  • how the fetal HR varies up and down around the baseline

accelerations:

  • periods where the fetal HR spikes

decelerations:

  • periods where the fetal HR drops
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10
Q

What is the normal rate for contractions?

A

4 or 5 contractions should occur every 10 mins whilst in labour

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11
Q

Why is it important to interpret uterine contractions?

A
  • contractions are used to gauge the actvity of labour
  • too few contractions indicates that labour is not progressing
  • too many contractions indicates uterine hyperstimulation + risk of fetal compromise
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12
Q

What is a normal baseline rate?

A

110 - 160 bpm

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13
Q

What is a normal value for variability?

A

5 bpm or more

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14
Q

How can baseline rate and variability be described?

A
  • reassuring
  • non-reassuring
  • abnormal
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15
Q

What is a reassuring baseline rate / variability?

A

baseline rate:

  • between 110 - 160 bpm

variability:

  • between 5 - 25
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16
Q

What is a non-reassuring baseline rate / variability?

A

baseline rate:

  • 100 - 109 bpm

OR

  • 161 - 180 bpm

variability:

  • < 5 for 30-50 mins

OR

  • > 25 for 15-25 mins
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17
Q

What is an abnormal baseline rate / variability?

A

baseline rate:

  • below 100 or above 180

variability:

  • < 5 for over 50 mins

OR

  • > 25 for more than 25 mins
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18
Q

What is an acceleration?

A
  • a rise of > 15bpm for 15 seconds
  • accelerations occurring alongside uterine contractions is a sign of a healthy fetus

the absence of accelerations with an otherwise normal CTG is not necessarily a concerning sign

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19
Q

What is a deceleration?

A
  • a fall of > 15 bpm for > 15 seconds
  • this is a sign of fetal distress
20
Q

What aspects of uterine contractions are assessed?

A
  • count how many contractions occur in 10 mins (each square = 1 min)
  • assess duration of the contractions
  • assess intensity by palpating the abdomen

the CTG does NOT give any indication of contraction intensity

this must be gauged by palpating the abdomen

21
Q

How is the baseline rate calculated?

A
  • look at the CTG and assess what the average heart rate has been over the last 10 mins
  • ignore any accelerations or decelerations
22
Q

How is variability calculated?

A
  • by assessing how much the peaks / troughs of the HR deviate from the baseline rate
23
Q

Why are decelerations a concerning sign?

A
  • the fetal HR drops in response to hypoxia
  • it is slowing down to conserve energy for vital organs
24
Q

What are the 4 types of deceleration?

A
  1. early decelerations
  2. late decelerations
  3. variable decelerations
  4. prolonged decelerations
25
Q

What are early decelerations?

A
  • early decelerations are related to uterine contractions
  • they start when the contraction begins and recover when the contraction stops
26
Q

What causes an early deceleration?

A
  • the uterus compresses the fetal head, which stimulates the vagus nerve and slows the HR
  • this is NOT pathological
27
Q

What is a late deceleration?

A

late decelerations begin at the peak of uterine contraction and recover when the contraction ends

28
Q

What causes a late deceleration?

A

insufficient blood flow to the uterus + placenta due to:

  • maternal hypotension
  • pre-eclampsia
  • uterine hyperstimulation

this can result in fetal hypoxia + acidosis

29
Q

What are variable decelerations?

A
  • a rapid fall in baseline fetal HR with a variable recovery phase
  • their duration is variable and they do NOT have a relationship to uterine contractions
30
Q

Describe the course of a variable deceleration

A
  • there is a fall of > 15 bpm from the baseline
  • the lowest point of the deceleration occurs within 30 seconds
  • the deceleration lasts for < 2 mins in total
31
Q

How are variable decelerations described?

A

in terms of depth and duration

32
Q

What do variable accelerations indicate?

A
  • intermittent compression of the umbilical cord, causing fetal hypoxia
  • they are normally seen during labour + in women with reduced amniotic fluid volume
33
Q

What are the shoulders of deceleration?

A
  • accelerations that occur before and after a variable decleration
  • their presence indicates the fetus is not yet hypoxic + is adapting to redcued blood flow
34
Q

What is a prolonged deceleration?

A

a decleration that lasts for more than 2 minutes

35
Q

When is a CTG described as reassuring in terms of decelerations?

A
  • there are no declerations
  • there are early decelerations
  • there are < 90 seconds of variable decelerations with no concerning features
36
Q

What features of decelerations can make then non-reassuring or abnormal?

A
  • regular variable decelerations / late decelerations can be abnormal or non-reassuring depending on their features
  • prolonged decelerations are always abnormal
37
Q

How can a CTG be categorised based on baseline rate, declerations + variability?

A

normal

suspicious:

  • a single non-reassuring feature

pathological:

  • 2 non-reassuring features

OR

  • a single abnormal feature

need for urgent intervention:

  • acute bradycardia

OR

  • prolonged decleration for > 3 mins
38
Q

What is the “rule of 3s” for fetal bradycardia?

A
  • 3 mins - call for help
  • 6 mins - move to theatre
  • 9 mins - prepare for delivery
  • 12 mins - delivery of the baby (by 15 mins)
39
Q

What is a sinusoidal CTG pattern?

A
  • indicates severe fetal compromise
  • pattern is similar to a sine wave
  • stable baseline rate around 120-160bpm with no beat to beat variability
40
Q

What can a sinusoidal CTG indicate?

A
  • severe fetal hypoxia
  • severe fetal anaemia
  • fetal / maternal haemorrhage
41
Q

What is fetal bradycardia?

When does it become more concerning?

A
  • a baseline HR < 110 bpm
  • severe prolonged bradycardia occurs when the HR < 80 for more than 3 mins
42
Q

What are the causes of prolonged severe bradycardia?

A
  • prolonged cord compression
  • cord prolapse
  • epidural / spinal anaesthesia
  • maternal seizures
  • rapid fetal descent
43
Q

When is it normal to have a baseline rate of 100-120bpm?

A
  • postdate gestation

OR

  • occipitoposterior / transverse presentations
44
Q

What are the possible causes of reduced variability?

A
  • fetal sleeping (should last < 40 mins)
  • fetal acidosis (due to hypoxia)
  • fetal tachycardia
  • drugs
  • prematurity (reduced < 28 weeks gestation)
  • congenital heart abnormalities

fetal acidosis is more likely if decelerations are also present

45
Q

What drugs are associated with reduced variability?

A
  • methyldopa
  • opiates
  • benzodiazepines
  • magnesium sulphate
46
Q

What would you want to do if a CTG was non-reassuring or abnormal?

A

fetal blood sample

  • this assesses for fetal acidosis
  • determines the need for emergency LSCS

Y4 - GOSH (62 decks)

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