Cardiotocography_Flashcards

Question 1

What does cardiotocography (CTG) record?

Answer 1

CTG records pressure changes in the uterus using internal or external pressure transducers.

Question 2

What is the normal fetal heart rate?

Answer 2

The normal fetal heart rate varies between 100-160 / min.

Question 3

What is baseline bradycardia in CTG?

Answer 3

Heart rate < 100 /min.

Question 4

What are the causes of baseline bradycardia in CTG?

Answer 4

Increased fetal vagal tone, maternal beta-blocker use.

Question 5

What is baseline tachycardia in CTG?

Answer 5

Heart rate > 160 /min.

Question 6

What are the causes of baseline tachycardia in CTG?

Answer 6

Maternal pyrexia, chorioamnionitis, hypoxia, prematurity.

Question 7

What is loss of baseline variability in CTG?

Answer 7

< 5 beats / min.

Question 8

What are the causes of loss of baseline variability in CTG?

Answer 8

Prematurity, hypoxia.

Question 9

What is early deceleration in CTG?

Answer 9

Deceleration of the heart rate which commences with the onset of a contraction and returns to normal on completion of the contraction.

Question 10

What causes early deceleration in CTG?

Answer 10

Usually an innocuous feature indicating head compression.

Question 11

What is late deceleration in CTG?

Answer 11

Deceleration of the heart rate which lags the onset of a contraction and does not return to normal until after 30 seconds following the end of the contraction.

Question 12

What causes late deceleration in CTG?

Answer 12

Indicates fetal distress, e.g., asphyxia or placental insufficiency.

Question 13

What are variable decelerations in CTG?

Answer 13

Decelerations independent of contractions.

Question 14

What causes variable decelerations in CTG?

Answer 14

May indicate cord compression.

Question 15

summarise

Answer 15

Question 16

A Cardiotocogram (CTG) is performed on a 28-year-old female at 36 weeks gestation who has attended labour ward in spontaneous labour. The CTG shows a foetal heart rate of 120bpm and variable decelerations and accelerations are present. There are no late decelerations. However, the midwife notices a 20 minute period where the foetal heart rate only varies by 3-4bpm. The mum is concerned as she has not felt her baby move much for about 20 mins and would like to know what the likely cause is. She starts crying when she tells you that she took some paracetamol earlier as she was in so much pain from the contractions and is worried this has harmed her baby. Which of the following is the most likely cause of this decreased variability?

Prematurity
Foetal acidosis
Foetus is sleeping
Foetal tachycardia
Side effect of the paracetamol

Answer 16

Foetus is sleeping

The most common explanation for short episodes (< 40 minutes) of decreased variability on CTG is that the foetus is asleep. However, if the decreased variability lasts for more than 40 minutes, we start to worry. Other causes of decreased variability in foetal heart rate on CTG are due to maternal drugs (such as benzodiazepines, opioids or methyldopa - not paracetamol), foetal acidosis (usually due to hypoxia), prematurity (< 28 weeks, which is not the case here), foetal tachycardia (> 140 bpm, again not the case here) and congenital heart abnormalities.

Question 17

A 31-year-old female is undergoing cardiotocography (CTG) monitoring during labour. Which of the following would be considered an ‘abnormal’ feature of the CTG tracings?

Baseline heart rate of 160 beats/minute
Baseline variability of 5 or more beats/minute
Fetal heart rate accelerations
A single prolonged deceleration lasting 3 minutes or more
Variable decelerations occurring with over 50% of contractions with response to conservative management

Answer 17

A single prolonged deceleration lasting 3 minutes or more

There are three categories: normal, non-reassuring and abnormal. Note the question asks for an abnormal feature.

A single prolonged deceleration lasting 3 minutes or more is considered abnormal.

A heart rate of 160 is in the range of normal/reassuring (100-160).

Variable decelerations occurring with over 50% of contractions may be non-reassuring or abnormal depending on their response to conservative treatment.

Source: NICE guidelines (https:www.nice.org.uk/guidance/cg190/chapter/1-recommendations#initial-assessment)