Basic Practical Skills - Obstetrics Flashcards
What is the function of the cardiotocography (CTG)?
Used during pregnancy to monitor fetal heart and uterine contractions
- detects early signs of fetal distress
- commonly used in third trimester
What should be done in the event of an abnormal CTG?
Invasive investigations
Emergency C-section considered early
How are CTGs read?
Dr - define risk C - contractions Bra - baseline rate V - variability A - accelerations D - decelerations O - overall impression
How do you define risk when reading a CTG?
Is pregnancy high or low risk (high risk pregnancies have lower threshold for intervention) Maternal factors - gestational diabetes - hypertension - asthma Obstetric complications - multiple gestation - post-date gestation - previous C-section - IUGR - premature rupture of membranes - congenital malformations - induced/augmented labour - pre-eclampsia Other factors - no antenatal care - smoking - drug abuse
How are contractions assessed on CTG?
Number of contractions in a 10 minute period (big square on CTG = 1 minute)
Individual contractions are seen as peaks on CTG monitoring - uterine acitvity
Assess for
- duration
- intensity (can only be assessed using palpation)
How is the baseline rate assessed on CTG?
Average heart rate of a fetus within a 10 minute window (ignoring accelerations and decelerations)
- normal HR 110-150bpm
What are the causes of fetal tachycardia (>160bpm) on CTG
Fetal hypoxia Chorioamnionitis - maternal fever Hyperthyroidism Fetal or maternal anaemia Fetal tachyarrhythmia
Causes of fetal bradycardia (<100bpm) on CTG
Mild bradycardia (100-120bpm) is common in postdate gestation or in occiput posterior or transverse presentation
Severe prolonged (<80bpm for more than 3 mins) bradycardia
- prolonged cord compression
- cord prolapse
- epidural and spinal anaesthesia
- maternal seizure
- rapid fetal decent
How is fetal bradycardia managed?
If the cause can’t be corrected - immediate delivery of fetus is required
How is variability assessed on CTG
Variation of fetal heart rate from one beat to the next
- occurs due to interaction between nervous system, chemoreceptors, cardiac responsiveness and baroreceptors
- a healthy fetus constantly adapts to changes in the environment
Normal between 5-25bpm above/below baseline
- less than 5bpm variation for >50 mins is abnormal
- more than 25 bpm variation for >25 min is abnormal
What are the causes of reduced variability
Fetus sleeping (<40 mins normal) Fetal acidosis due to hypoxia Tachycardia Drugs - opiates and benzos Prematurity - before 28 weeks Congenital heart abnormalities
How are accelerations assessed on CTG
Abrupt increase in baseline heart rate >15bpm for >15 seconds
- presence is reassuring
- healthy = occurs alongside contractions
How are declarations assessed on CTG
Abrupt decrease in baseline heart rate >15bpm for >15 seconds
Can be pathological/non-pathological depending on the situation
When are decelerations normal on a CTG
During labour
- timed with contractions (early decelerations) due to increased fetal intracranial pressure
- increased vagal tone
What are variable declarations on a CTG
Variable decelerations are a rapid fall in baseline heart rate and variable recovery phase
- variable in duration
- aren’t related to contractions
Require close monitoring if become persistent
Presence of accelerations as well are reassuring
What are the causes of variable decelerations on CTG
Umbilical cord compression
- vein occluded first: initially causes an acceleration in response
- artery occluded next: rapid deceleration
Can resolve if the mother change position (baseline rate returns once pressure is released)
How are late decelerations assessed on CTG
Begin at the peak of contractions and recover once contraction has ended
Indication of insufficient blood flow to the uterus and placenta
- fetal hypoxia and acidosis
Fetal sampling needed to assess severity
- if acidotic, emergency C-section is required
Causes of late decelerations on CTG
Maternal hypotension
Pre-eclampsia
Uterine hyperstimulation
What are prolonged decelerations on CTG
2 or 3 minutes of deceleration (non-reassuring)
Over 3 minutes is very abnormal
What are sinusoidal decelerations on CTG
Smooth, regular, wave-like pattern on CTG Causes - severe fetal hypoxia - severe fetal anaemia - fetal or maternal hemorrhage
How is the overall impression of a CTG assessed
All aspects are assessed - determined by how many individual features are reassuring, suspicious or abnormal Give overall impression - reassuring - suspicious - abnormal Mention in notes
