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