CTG interpretation

What is a cardiotocography? (2)

Used during pregnancy to monitor fatal heart rate and uterine contractions

Commonly used in the 3rd trimester and its purpose is to monitor fetal well-being and detect early fetal distress

What may an abnormal CTG indicate?

The need for further investigations and intervention

How does a CTG work? (3)

It involves the placement of 2 transducers onto the abdomen of a pregnant woman

One transducer records the fetal heart rate using ultrasound

The other transducer monitors the contractions of the uterus by measuring the tension of the maternal abdominal wall (indirect indication of intrauterine pressure)

Who is the CTG assessed? (2)

1. Midwife

2. Obstetric medical team

What is a popular acronym used to interpret all aspects of a CTG?

DR C BRAVADO

Dr - define risk, C- contractions

Bra- baseline rate, v- variability, a-accelerations, d- decelerations, o-overall impression

When performing CRT interpretations what is the first thing to do?

Determine if the pregnancy is high / low risk (give the CTG reading more context)

How should you analyse uterine contractions?

1. Duration

2. Intensity (using palpation)

3. *each big square ie equal to 1 minute

Define hyperstimulation

More than 5 contractions in 10 minutes

What is the baseline rate of the average heart rate of the fetus?

Within a 10 minute window

What is the normal fetal heart rate?

110-160 bpm

Define fetal tachycardia

Baseline heart rate greater than 160 bpm

Potential causes of fetal tachycardia? (5)

1. Fetal hypoxia

2. Chorioamnionitis

3. Hyperthyroidism

4. Fetal / maternal anemia

5. Fetal tachyarrthmia

Define fatal bradycardia

Baseline heart rate of less than 100 bpm

When is it common to have a baseline heart rate of 100-120 bpm? (3)

1. Postdate gestation

2. Occipiut posterior / transverse presentations

3. Severe prolonged bradycardia (<80 bpm for +3 mins) > indicates severe hypoxia

What are the causes of prolonged severe bradycardia?®

1. Prolonged cord compression

2. Cord prolapse

3. Epidural and spinal anaesthesia

4. Maternal seizures

5. Rapid fetal descent

What is the variability a result of? (4)

Interactions between:

1. Nervous system

2. Chemoreceptors

3. Baroreceptors

4. Cardiac responsiveness

   *intact neurological system in fetus

What is the normal variability?

5-25 bpm

What are the categories of variability? (3)

1. Reassuring > 5- 25 bpm

2. Non-reassuring > less than 5bpm for 30-50 mins / +25 bpm for 15-25 mins

3. Abnormal > less than 5 bpm for +50 mins / +25bpm for +25 mins/ sinusoid

What are the causes of reduced variability?(6)

1. Fetal sleeping (no longer than or mins) > most common cause

2. Fetal acidosis (due to hypoxia)

3. Fetal tachycardia

4. Drugs> opiates, benzodiazepines, methlyodpa, MgSO4

5. Prematurity (<28 weeks)

6. Congenital heart abnormalities

Define accelerations

Abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds, this is reassuring when occurring alongside uterine contractions

Define decelerations

Abrupt decrease in the baseline fatal heart of greater than 15 bpm for greater than 15 seconds

Which system is the fetal heart rate controlled by? (2)

1. Autonomic and somatic nervous system

Define early decelerations and the cause

Uterine contractions begins and recover then uterine contractions stop (Physiological)

Cause > fetal intracranial pressure causing increased vagal tone

Define variable deceleration and the cause

Rapid fall in baseline fetal heart rate with a variable recovery phase (no relationship to uterine contractions)

Cause - umbilical cord compression

Define late deceleration and the causes (3)

Begins ate the peak of the uterine contraction and recovers after the contraction ends due to reduced uteroplacental blood flow

Causes - maternal hypotension, pre-eclampsia, uterine hyperstimulation

Define prolonged deceleration

Deceleration that lasts more than 2 minutes

Between 2-3 mins is non-reassuring

Longer than 3 minutes is abnormal

Which CTG pattern is rare and is associated with high rates of fetal morbidity & mortality?

Sinusoidal pattern

What are the characteristics of a sinusoidal pattern? (4)

1. Smooth, regular, wave-like pattern

2. Frequency of around 2-5 cycles in a minute

3. Stable baseline rate around 120-160 bpm

4. No neat to beat variability

What does a sinusoidal pattern usually indicate?(3)

1. Severe fetal hypoxia

2. Severe fetal anaemia

3. Fetal/ maternal haemorrhage