Fetal Monitoring In Labour

Question 1

What device is used?

Answer 1

A cardiotocograph

Question 2

How is a CTG done?

Answer 2

Placement of 2 transducers onto abdomen
One records fetal heart rate using ultrasound and the other transducer monitors the contractions of the uterus by measuring the tension of the maternal abdominal wall - an indirect indication of intrauterine pressure

Question 3

What is the acronym used to read a CTG?

Answer 3

DR: define risk 
C: contractions 
BRA: baseline rate 
V: variation ps
A: accelerations 
D: decelerations 
O: overall impression

Question 4

What does define risk mean?

Answer 4

The need to determine whether the pregnancy is high or low risk
Gives more context to the CTG

Reasons for high risk:
Maternal medical illness - asthma, HTN, GDM
Obstetric complications - post date, previous CS, IUGR, PROM, congenital malformations, IOL, pre-eclampsia
Others: smoking, drug abuse, absence of prenatal care

Question 5

What should be assessed with regards to contractions?

Answer 5

The number present in a 10 minute period
Individual contractions = peaks on the part measuring uterine activity
Assess for:
Duration
Intensity - assessed using palpation

Question 6

What is the baseline rate?

Answer 6

The average HR of the fetus within a 10 min window 
Normal: 110-160bpm 
Fetal tachycardia: baseline HR> 160
If >180 = abnormal 
Fetal bradycardia: baseline <100

Question 7

What can cause fetal tachycardia?

Answer 7

Fetal hypoxia 
Chorioamnionitis 
Hyperthyroidism 
Fetal or maternal anaemia
Fetal tachyarrhythmia

Question 8

When is it common to have a baseline HR between 100-120?

Answer 8

Post date gestation

Occiput posterior or transverse presentations

Question 9

What does severe prolonged bradycardia indicate? (Less than 80bpm for more than 3 mins)

Answer 9

Severe hypoxia

Question 10

What causes of prolonged severe bradycardia are there?

Answer 10

Prolonged cord compression
Cord prolapse
Epidural and spinal anaesthesia 
Maternal seizures
Rapid fetal descent

Question 11

What does baseline variability refer to?

Answer 11

The variation of fetal HR from one beat to the next

Question 12

Variability occurs as a result of the interaction between…

Answer 12

The nervous system, chemoreceptors, baroreceptors and cardiac responsiveness
It is an indicator of how healthy fetus is in that moment in time, a healthy fetus will constantly be adapting its HR in repossessed to changes in the environment
Normal variability indicates an intact neurological system in fetus

Question 13

What is normal variability?

Answer 13

Between 5 and 25bpm

Question 14

How do you calculate variability?

Answer 14

Assess how much the peaks and troughs of the HR deviate from the baseline rate

Question 15

How can variability be categorised?

Answer 15

Reassuring: 5-25bpm
Non reassuring: less than 5bpm between 30-50mins, more than 25bpm for 15-25 mins
Abnormal: less than 5bpm for more than 50mins, more than 25bpm for more than 25 mins, sinusoidal

Question 16

What can cause reduced variability?

Answer 16

Fetal sleeping - should last no longer than 40mins (most common cause)
Fetal acidosis due to hypoxia - more likely if late decelerations also present
Fetal tachycardia
Drugs - opioids, benzodiazepines, methyldopa, magnesium sulphate
Prematurity - variability reduced afternoon earlier gestation
Congenital heart abnormalities

Question 17

What are accelerations?

Answer 17

An abrupt increase in the baseline rate greater than 15bpm for greater than 15 seconds

Question 18

Is the presence of accelerations reassuring?

Answer 18

Yes
Accelerations occurring alongside uterine contractions is a sign of a healthy fetus
The absence of accelerations with otherwise normal CTG is of uncertain significance

Question 19

What are decelerations?

Answer 19

An abrupt decrease in baseline HR of greater than 15bpm for greater than 15 seconds

Question 20

Why does the fetus reduce its HR in response to hypoxic stress?

Answer 20

To preserve myocardial oxygenation and perfusion

The reduction in HR to reduce myocardial demand is referred to as a deceleration- there are a number of different types

Question 21

What are early decelerations?

Answer 21

They start when contraction begins and recover when uterine contractions stops
Caused by increased fetal intracranial pressure causing increased vagal tone, quickly resolves once contraction ends and pressure reduces
Considered physiological

Question 22

What are variable decelerations?

Answer 22

Rapid fall in baseline HR with a variable recovery phase
They are variable in duration and may not relate to contractions
Most often seen in those with reduced amniotic fluid volume

Question 23

What are variable decelerations usually caused by?

Answer 23

Umbilical cord compression
Umbilical vein compressed first, causing acceleration of fetal HR. Then umbilical artery occluded causing subsequent rapid deceleration. When pressure on cord reduced, another acceleration occurs and baseline returns
Accelerations before and after deceleration = shoulders of deceleration
- there presence indicates fetus not yet hypoxic and is adapting to reduced flow

Question 24

Variable decelerations can sometimes be resolved if…

Answer 24

Mother changes position

Question 25

The presence of persistent variable decelerations indicates a need for…

Answer 25

Close monitoring

Question 26

Are variable decelerations without a shoulder more worrying?

Answer 26

Yes - suggests fetus becoming more hypoxic

Question 27

What are late decelerations?

Answer 27

They begin at the peak of the uterine contraction and recover after the contraction ends
Indicates that there is insufficient blood flow to the uterus and placenta as a result blood flow to fetus significantly reduced causing fetal hypoxia and acidosis

Question 28

Reduced uteroplacental blood flow can occur due to…

Answer 28

Maternal hypotension
Pre eclampsia
Uterine hyperstimulation

Question 29

What is a prolonged deceleration?

Answer 29

Lasting more than 3 mins
If lasts between 2-3 mins = non reassuring
Longer than 3 mins immediately classed as abnormal

Question 30

What is a sinusoidal pattern?

Answer 30

Rare, very concerning, high fetal morbidity and mortality 
Smooth wave like pattern
Frequency: 2-5 cycles per minute
Stable baseline around 120-160
No beat to beat variability

Question 31

What does a sinusoidal pattern indicate?

Answer 31

Severe fetal hypoxia
Severe fetal anaemia
Fetal/maternal haemorrhage

Question 32

How can the overall impression be classified?

Answer 32

Reassuring
Suspicious
Abnormal