Introduction
A cardiotocograph (CTG) is used in obstetrics as a method by which to monitor both the foetal heart and uterine contractions. CTG is used used in conjunction with partogram to monitor labour, but are also performed at some third trimester appointments. They are however quite cumbersome and perform.
Method
There are two sensors called transducers that are placed on, or in the mother.
- Fetal heart transducer >> Can be placed in the position the FH can best be heard with a Doppler sonicade, or alternatively can be placed on the fetal head when the cervix allows access to it. USEFUL TIP – The wire from this transducer is often striped, and watching the movement of the stripes can give a good impression of how hard the woman is pushing and how much progress she is making! This is not only good for the healthcare professionals, but for mother and any relatives, who can see that they are/aren’t making progress!
- Uterine pressure transducer >> This is placed over the uterine fundus. Although it is interpreted as uterine pressure, it measures the tension of the abdominal wall. It can be reset at any point, and although comparisons between contractions can be made based on the reading, it does not give the actual strength of the contraction, this is best gauged by an experienced hand on the abdomen feeling the uterus contract (talk to midwives and practice!).
Over the course of labour there is often a huge ream of paper churned out by the machine, and regular checks on the CTG ensure both adequate monitoring of the FH and contractions, and that paper doesn’t fill the room!
Interpretation
- Identify the patient, the time and the details of the pregnancy so far. At the start of every CTG the date, time, patient name, gestation, Parity and Gravidity, Pregnancy information (GDM, HTN, Increased BMI, multiple pregnancy etc)
- Use the acronym DR C BRaVADO
- DR – Define Risk = Low/High using risk factors above
- C – Contractions = Describe the maternal contractions, how frequent (aim for 4-5 every 10 minutes), the intensity, consistency within contractions, duration of contractions and the resting tone between contractions
- BRa – Baseline Rate = Normal Fetal heart rate (110-160 bpm), Tachy/bradycardia
- V – Variability = The baseline can fluctuate by around 10-15bpm. This is described as good variability. There may be periods of reduced variability, if these are for less than 40minutes this can often be attributed to sleep! However prolonged reduced variability is suspicious and must be investigated.
- A – Accelerations = These are normally a good sign! These are short periods of increased fetal heart rate of at least 15bpm for at least 15seconds. Just note the presence or absence of accelerations, if the acceleration if over 2 minutes it is known as a prolonged acceleration.
- D – Decelerations = Are they periodic (with contractions) or episodic (anytime). Early decellerations begins around the onset of contractions, and resolve by the end of them. These are not cause for concerns, they occur commonly and are normally a response to fetal compression. Late decelerations start some way through or after the contraction, and aren’t gone by the end. They are a sign of fetal hypoxia, normally through decreased placental blood flow. These are suspicious changes and further care must be taken to monitor the variability in conjunction with the baseline rate. Variable decelerations occur at any time, and are thought to occur due to umbilical cord compression. Many babies (up to 50%) get some variable decelerations at some point in labour.
- O– Overall impression = Is the CTG Reassuring, Suspicious or Pathological? Things that would make a CTG suspicious are decreased variability, progressing tachycardia, decrease in the baseline rate or late decelerations with good variability. Pathological signs are Persistent late decelerations with reduced variability, variable decelerations if prolonged or associated with other signs, little/no variability for prolonged periods, or severe bradycardia.
3. Give a management plan and document everything in the notes!