Fetal Monitoring Flashcards
What are the ways of monitoring a woman/baby during delivery and how do we decide which one is more appropriate?
Can either monitoring FHR intermittently with handheld doppler or can do it continuously with a CTG
- If a woman has any high risk factors (induction, meconium stained liquor, IUGR, multiple pregnancy etc.) or has had any complications during pregnancy then CTG monitoring is more appropriate
What does CTG stand for?
Cardiotocograph
What four things does the CTG show starting from the top and working down?
TOP - Fetal heart rate (most important)
- Maternal reported fetal movements
- Machine detected fetal movements
- Measurement of contractions
What mnemonic can be used to interpret a CTG?
DR C BRAVADO Determine Risk Contractions Baseline Rate Accelerations VAriability Decelerations Overall Impression
What is normal for contractions and what information does the CTG tell us / not tell us about contractions?
In active labour should expect 4-5 contractions every 10mins (one CTG strip is 10cm=10min)
CTG tells you when they are happening but does NOT tell you how intense they are (palpate uterus for this)
What is a normal Baseline Rate on a CTG?
100-160bpm
What is an acceleration and is it concerning?
It is classed as an acceleration when there is an increase of >15bpm for >15s
They are NOT concerning and usually just reflect fetal movements
Is this absence of accelerations concerning?
No - Usually just reflect periods of time when the baby is asleep
What is a normal variability on a CTG? Is variability reassuring?
> 5bpm
variability is important and is a reassuring feature
What are decelerations and are they concerning?
When there is a decrease by >15bpm for >15s
They can be concerning but are not necessarily - it depends on the type
What features of the deceleration are important to consider and what are the different types?
Their relation to contractions (early = just before, late = just after) Their shape (is it uniform or variable) Their depth Their recovery Their timing
TYPES: Variable, Early, Late
What’s the most common type of deceleration (safest to assume it’s this if you’re not sure)?
Variable - 95%
Why do decelerations occur? What is the most concerning cause of decelerations?
Compression of the head during contraction leads to vagus nerve stimulation leading to decelerations - not concerning
During contraction uterine blood vessels are compressed reducing perfusion to placental bed leading to deceleration
Umbilical cord can also be compressed
If this leads to considerable hypoxia then this can have a hypoxic effect on fetal myocardium - this is concerning
This is why some decelerations are not concerning - they represent normal fetal response to contractions and transient relative hypoxia
Which decelerations are the least concerning?
Early decelerations - they are uniform and occur just before / with a contraction - associated with vagal nerve compression
What decelerations are more concerning and why?
Late decelerations - late symmetry with contraction
They are more associated with fetal hypoxia and the longer they last, deeper they are and later they come after the contractions he more associated they are with metabolic acidosis
Are variable decelerations concerning?
Depends on how deep and how wide they are:
- If it lasts for longer than 60s OR
- Does not re-establish baseline quickly OR
- There is reduced variability throughout
THESE ARE CONCERNING FEATURES
How long would a single deceleration have to last before it was extremely concerning?
3mins or longer
What are some disadvantages of CTG?
There is a very high false positive rate - 10% of abnormal CTGs will be occurring in a normal fetus
If faced with an abnormal CTG what are your first steps?
Change maternal position - could be due to aorta-caval compression so put her in L lateral
Give fluids
Consider fetal scalp manipulation
Consider fetal blood sampling
How dilated does the woman have to be before you can take a fetal blood sample (FBS)?
> 3cm
What are the pH parameters in a fetus?
>7.25 = Normal 7.20-7.25 = Borderline - monitor closely <7.20 = Urgent delivery required. Suggests considerable hypoxia
What are the base excess parameters in fetus?
> -6 = normal
-6.1- -7.9 = Borderline
What are some other indications for FBS?
Persistent or late decelerations on CTG
Persistent fetal tachycardia
Prolonged and persistent early decelerations
Meconium stained liquor + ANY CTG abnormality
Prolonged loss of variability (<5bpm)
