WK5: fetal surveillance Flashcards
Define IA
the auscultation of the fetal heart using a hand-held Doppler at regular intervals and for a pre-defined duration during labour.
How frequently should IA be completed in lanour?
- Every 15-30 minutes in the active phase of the first stage of labour
- With each contraction or at least every five minutes in the active second stage of labour.
What are some key practice point of IA in labour?
- Each auscultation episode should commence toward the end of a contraction and be continued for at least 30-60 seconds after the contraction has finished. (document resting fetal health when out of contraction)
Auscultation in labour should be undertaken and documented:
First stage: Every 15-30 minutes in the active phase of the first stage of labour.
Active second stage: With each contraction or at least every five minutes
What is the normal baseline range for fetal heart rate? and what may change this and when should it be assessed?
Baseline= 110-150 BPM
Younger gestational age will sit higher than older fetus’
Assessed in the absence of
- fetal movements
- uterine activity
- and decelerations
What is normal, increased, reduced and absent variability?
Absent: <3 BPM
Reduced: 3-5 BPM
Normal: 6-25 BPM
Increased >26 BPM
Define an acceleration
The increase from the baseline of 15 BPM for 15 seconds.
Transient increases in FHR of 15 bpm or more above the baseline and lasting 15 seconds
at the baseline. Accelerations in the preterm fetus may be of lesser amplitude and shorter
duration. The significance of no accelerations on an otherwise normal CTG is unclear.
What is considered a decel?
a drop in FHR for >/15 secs
Transient decreases of the FHR below the baseline lasting at least 15 seconds, conforming
to one of the patterns e.g. early, later, variable, complicated variable, prolonged, bradycardia.
What are some abnormalities that when they occur alone or unlikely to relate to fetal compromise?
- Baseline rate 100-109 bpm.
- Reduced or reducing baseline variability 3-5bpm.
- Absence of accelerations.
- Early decelerations.
- Variable decelerations without complicating features.
What are some features that are associated with fetal compromise and demand action?
- Baseline fetal tachycardia >160 bpm.
- Rising baseline fetal heart rate (including where it remains within normal range).
- Complicated variable decelerations.
- Late decelerations.
- Prolonged decelerations (a fall in the baseline fetal heart rate for more than 90 seconds and up to 5 minutes).
MORE URGENT ATTENTION= - Bradycardia (a fall in the baseline fetal heart rate for more than 5 minutes).
- Absent baseline variability <3bpm.
- Sinusoidal pattern.
- Complicated variable decelerations with reduced or absent baseline
variability. - Late decelerations with reduced or absent baseline variability.
Define tachysystole
= more than five active labour contractions in ten minutes, without fetal heart rate abnormalities.
Define uterine hypertonus
= contractions lasting longer than two minutes in duration or contractions occurring within 60 seconds of each other, without fetal heart rate abnormalities.
Define uterine hyperstimulation
Excessive uterine activity, (either tachysystole or uterine hypertonus) WITH fetal heart rate abnormalities.
What is the appropriate management for tachysystole and hypertonus?
- continuous cardiotocography;
- consideration of reducing or ceasing oxytocin infusion;
- maternity staff remaining with the woman until normal uterine activity is observed; and
- consideration of tocolysis
- reposition mother
- VE to see if fully dilated and can push
What is the appropriate management for uterine hyperstimulation?
- continuous cardiotocography;
- reducing or ceasing oxytocin infusion;
- maternity staff remaining with the woman until normal
uterine activity is observed; - consideration of tocolysis; and
- consideration of urgent delivery
- Excessive uterine activity in the absence of evidence of fetal
compromise is not in itself an indication for tocolysis.
Define sinusoidal
A regular oscillation of the baseline FHR resembling a sine wave.
- absent baseline variability or accelerations
- a relatively fixed rate of 2‐5 cycles per minute
- typically, an amplitude of 5‐15 beats
- reduced fetal movements is a key clinical feature
- is usually indicative of severe fetal anaemia (Hb < 50g/L)
- may not start out as an overt sinusoidal pattern!
- there is nothing normal about a true sinusoidal pattern!
This smooth, undulating pattern is persistent, has a relatively fixed period of 2 –5 cycles per minute and an amplitude of 5 –15 bpm above and below the baseline. Baseline variability is absent and
there are no accelerations.
Define baseline fetal heart
The mean level of the fetal heart rate when this is stable, excluding accelerations and
decelerations and contractions. It is typically determined over a time period of 5 or 10
minutes and expressed in bpm. Preterm fetuses tend to have values towards the upper end
of this range. A progressive rise in the baseline is important as well as the absolute values.
Define an early decel
Uniform, repetitive decrease of FHR with slow onset early in the contraction and slow return
to baseline by the end of the contraction.
- uniform in shape
- typically seen in sleep
Are benign
Define variable decels
Repetitive or intermittent decreasing of FHR with rapid onset and recovery. Time relationships with contraction cycle may be variable but most commonly occur simultaneously with contractions
Cause: cord compression
- variable in time, duration and depth.
- typically have rapid onset and recovery
Define complicated variable decels
Variable decels with the following additional features which increase the likelihood of fetal hypoxia:
- Rising baseline rate
- Reducing or absent baseline variability.
- baseline fetal tachycardia.
- Slow return to baseline FHR after the end of the contraction.
- Large amplitude (by 60 bpm or to 60 bpm) and/or long duration
(60 seconds).
- a smooth post deceleration overshoot
- a slow return to the baseline after the contraction
- Presence of smooth post deceleration overshoots (temporary smooth increase in FHR above baseline).
Define prolonged decels
A fall in the baseline fetal heart rate for more than 90 seconds and up to 5 minutes
Define bradycardia
A fall in the baseline fetal heart rate for more than 5 minute
Define late decels and state what causes them.
Uniform, repetitive decreasing of FHR with, usually, slow onset mid to end of the contraction and nadir more than 20 seconds after the peak of the contraction and ending after the contraction.
= decelerations of any depth are significant if the fetus is hypoxic
In the presence of a non-accelerative trace with baseline variability <5 bpm, the definition would include decelerations of <15 bpm.
Cause: contractions in the presence of hypoxia
What is the criteria for a normal antenatal trace?
- A baseline fetal heart rate of 110‐160 bpm
- Normal baseline variability ≥ 6bpm and ≤ 25bpm
- 2 accelerations within a 20 minute period (reactivity)
- No decelerations
What is the criteria for a normal intrapartum trace?
- A baseline fetal heart rate of 110‐160 bpm
- Normal baseline variability ≥ 6bpm and ≤ 25bpm
- accelerations
- no decels
What does normal baseline variability indicate?
Normal baseline variability represents the continuous
interaction and balancing between the
- sympathetic nervous system
- parasympathetic nervous system
Normal baseline variability is therefore highly indicative of adequate CNS oxygenation
What does a normal vs abnormal trace indicate?
Normal trace-> well oxygenated fetus
Abnormal trace-> 60% ‐ 70%+ false positive
rate for hypoxia
What causes a bradycardia?
- maternal hypotension
- prolonged umbilical cord compression
- uterine hyperstimulation
- sustained fetal hypoxia of any cause
What causes a base line bradycardia?
- a mature parasympathetic system
- fetal heart conduction defect
What is the difference between a baseline brady and a brady?
A baseline bradycardia is a baseline that is below 110 BPM.
A Bradycardia is a fall in baseline of FHR for more than 5 minutes.
Define a tachycardia
A baseline fetal heart rate of more than 160 bpm
This range of baseline, is not associated with hypoxia in the presence of accelerations or with normal variability and no decelerations
What can cause a tachycardia?
- maternal tachycardia
- maternal fever (dehydration is a complicating
factor) - drugs e.g. salbutamol, terbutaline, atropine
- fetal tachyarrhythmia
- infection e.g. chorioamnionitis
- hypoxia (mild and compensating)
What causes Prolonged decels?
- hypoxia
that results from;
- prolonged contractions
- epidural insertion
- uterine hyperstimulation
- supine hypotension
- ruptured uterus
- abruption
- VE
*significance depends don’t he clinical picture
Explain how a contractions compromises a fetus
- Contraction onset
- reduced in intervillious space blood flow
- Insufficient O2 transfer into the fetus
- fetal O2 reaches a level low enough to result in myocardial depression
- deceleration occurs after the onset of the conraction
- uterine contraction begins to subside
- intervillous space blood flow improves
- fetal O2 levels begin to rise
- FHR returns to baseline after the contraction has finished
What CTG feature is indicative of sever fetal anemia?
Sinusoidal patterns
What must be included in a CTG report?
Baseline: the rate should be recorded
Baseline variability: normal, reduced, absent or
increased
Accelerations: present or absent
Decelerations: type, frequency, depth and duration
Uterine activity: frequency, strength, duration and rest
Management, including escalation
