Foetal Procedures Flashcards
What is a CTG?
Cardiotocography. This is used during pregnancy and labour to monitor the foetal heart rate and contractions of the uterus. It is most commonly used in the third trimester and its purpose is to monitor foetal wellbeing and detect foetal distress.
How does a CTG work?
It has two transducers to monitor foetal heart rate (ultrasound) and uterine contractions.
How should one read a CTG?
DR C BRAVADO
DR: define risk C: contractions BRa: Baseline rate V: variability A: accelerations D: decelerations O: overall impression
How does one define risk?
Maternal medical illness
- GDM
- PIH
- Asthma
Obstetric complications
- Multiple pregnancy
- Post-dates
- IUGR
- PROM
- Pre-eclampsia
Other risk factors
- No prenatal care
- Smoking
- Drug abuse
How does one interpret the contractions?
Contractions per 10 minutes
Duration: how long do they last
Intensity: how strong are they (palpation)
How does one interpret the baseline rate?
Average heart rate of the foetus within a 10 minute window. The normal is between 110 and 160 bpm.
Foetal tachycardia (>160 bpm)
- Hypoxia
- Chorioamnionitis
- Hyperthyroidism
- Foetal/maternal anaemia
Foetal bradycardia (<100 bpm for >3 minutes)
- Post-dates
- OP or transverse presentations
Severe bradycardia (<80 bpm for >3 minutes)
- Cord compression
- Cord prolapse
- Epidural/spinal anaesthesia
- Maternal seizures
- Rapid foetal descent
How does one interpret the variability?
This is the variation of the foetal heart rate from one beat to the next. The normal is between 5 and 25 bpm.
Non-reassuring:
- <5 bpm for 30-50 minutes
- > 25 bpm for 15-25 minutes
Abnormal:
- <5 bpm for > 50 minutes
- > 25 bpm for > 25 minutes
Reduced variability can be caused by:
- Foetal sleeping
- Foetal acidosis (hypoxia)
- Foetal tachycardia
- Drugs (opiates, BZDs, magnesium sulphate)
- Prematurity
How does one interpret accelerations?
These are an abrupt increase in the baseline heart rate by over 15 bpm for longer than 15 seconds.
These are signs of a healthy foetus but their absence on an otherwise normal CTG has no certain significance.
How does one interpret decelerations?
These are the abrupt decrease in the baseline heart rate by more than 15 bpm for longer than 15 seconds. They can be early, variable or late.
Early:
- Start and end within a contraction
- These are considered to be physiological and not pathological
Variable:
- A rapid fall in the baseline with a variable recovery rate
- Do not have a relationship to uterine contractions
- Umbilical cord compression
Late deceleration:
- Begin at the peak of uterine contractions and recover after the contraction ends
- Indicates insufficient blood flow from placenta to foetus
- Maternal hypotension, pre-eclampsia, uterine hyperstimulation
- Foetal blood sampling is required here
Prolonged deceleration:
- A deceleration lasting longer than 2 minutes
- A deceleration lasting longer than 3 minutes needs emergency action
Sinusoidal pattern:
- This is very rare but very concerning
- Severe foetal hypoxia or anaemia
- Foetal or maternal haemorrhage
- Emergency caesarean, outcome poor
How can one define the overall impression of a CTG?
It can either be reassuring, non-reassuring or abnormal.
When are growth scans performed?
The normal scans are performed at 10-13+6 weeks and at 18-22+6 weeks.
Indications for further growth scans include:
Current pregnancy:
- Uterus large/small for dates
- Reduced foetal movements
- Static growth
- Maternal smoking or drug misuse
- Multiple pregnancies
Obstetric history:
- Previous IUGR
- Previous unexplained still birth
Maternal disease:
- Diabetes
- Chronic disease
- Large fibroids
- BMI >35
What is measured in the anomaly scan?
- Head circumference
- Abdominal circumference
- Length of the long bones
- Volume of amniotic fluid
- Position of placenta
- Pressures and directions of flow of umbilical artery, middle cerebral artery
When is a doppler performed?
It is performed at ANC to measure foetal heart rate. It can also be combined with the US to doppler the arteries (umbilical, middle cerebral).
Indications include:
- Low foetal weight
- Oligohydramnios
How can foetal blood sampling be performed?
Antenatal:
- Needle into umbilical artery
- Needle into liver or heart
In labour:
- Make a cut into the scalp and collect using a capillary tube
What are the indications for foetal blood sampling?
- Pathological CTG
- Suspected acidosis in labour
