Fetal Monitoring Flashcards
What are the ways of monitoring a woman/baby during delivery and how do we decide which one is more appropriate?
For low risk pregnancies, FHR can be monitored intermittently with handheld doppler
High risk factors need continuous CTG monitoring
- Induction/oxytocin infusion
- Meconium stained liquor
- IUGR
- Multiple pregnancy
- Abnormality on intermittent monitoring
If the CTG doesn’t provide a satisfactory trace, how else can you measure FHR?
When is this alternative method contraindicated?
- If CTG isn’t satisfactory (high BMI, scaring, twins) you can use fetal scalp electrode to monitor FHR
- cant use if cervix is closed/membranes intact/thrombophilia/blood borne virus infection
What does CTG stand for?
What four things does the CTG show starting from the top and working down?
Cardiotocograph
A - fetal heart rate - variability
B - when mother feels baby moving
C - when computer feels baby moving
D - maternal contraction -tocograph - every ten minutes. Measures frequency and duration, not intensity (peaks don’t indicate strength)
What mnemonic can be used to interpret a CTG?
DR C BRAVADO Determine Risk Contractions (frequency, regularity, 'i would palpate') Baseline Rate Accelerations VAriability Decelerations Overall Impression **either normal and reassuring, non reassuring or abnormal**
What is normal for contractions and what information does the CTG tell us / not tell us about contractions?
In active labour should expect 4 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
- Healthy
Is this absence of accelerations concerning?
No - accelerations are NOT concerning and usually just reflect fetal movements and good oxygenation (absence is also not concerning-just sleeping)
What is a normal variability on a CTG? Is variability reassuring?
-how squiggly is the line?
>5bpm is ideal (either, <5, 5 or >5)
-variability is important and is a reassuring feature, reassure of autonomic system (rise and fall with para and sympathetic system)
-prolonged periods (>40 mins) may be due to hypoxia and inability of pons to control autonomic system
What are decelerations and are they concerning?
- When there is a decrease by >15bpm for >15s
- Indicate baby is under mechanical or hypoxic stress
What features of the deceleration are important to consider and what are the different types?
Their relation to contractions (early = just before/with, 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%
-they vary in timing to contractions OR vary in shape (morphology)
Why do decelerations occur?
- 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
(shoulder shrugging sign)
What decelerations are more concerning and why?
Late decelerations - late symmetry with contraction
They are more associated with fetal hypoxia (heart doesn’t beat as affectively) 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?
What are atypical features?
Depends on how deep and how wide they are.
(broader and deeper=concerning)
Atypical features
- If it lasts for longer than 60s OR >60bmp
- Does not re-establish baseline quickly OR
- There is reduced variability throughout <5
THESE ARE CONCERNING FEATURES
How long would a single deceleration have to last before it was extremely concerning?
3mins or longer (bradycardia)
-if not recovered by 9 mins-rapid delivery
What features must decelerations have to be truly classed as early/late
- uniformity (same morphology)
- same timing in relation to contraction
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, may be dehydrated
- Consider fetal scalp stimulation - heart rate increases reassuring
- Consider fetal blood sampling ABG (do 2)
- Delivery (with vaginal exam)
What does Fetal blood sample measure?
How dilated does the woman have to be?
- FBS measures fetal pH
- Woman must be >3cm dilated
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?
FBS good for when concerned about CTG, but delivery not imminent:
- 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)
What are some disadvantages of CTG?
There is a very high false positive rate - 10% of abnormal CTGs will be normal
