CTG Flashcards
what is CTG and what is it used for?
CTG= cardiotocography
Looks at fetal heart rate over time
used as a measure of fetal wellbeing both in the antenatal period and during labour
what are the 4 parameters of a CTG?
- baseline HR 2. variability 3. accelerations 4. decelerations
you look at a CTG and it appears like a sawtoothed/sinusoidal pattern.
what do you think of?
fetal anemia
why do we see variability on a CTG?
due to the waxing and waning nature of sympathetic and parasympathetic nervous stimulation in the fetus
what forms of variability indicate hypoxia on a CTG?
increased variability- >25bpm and less than 3bpm
what are some causes of reduced variability on a CTG?
think SSSS!
Sleep
Sick (hypoxia)
Submature (prematurity)
Sedation (drugs)
normal values for variability on a CTG?
5-25 bpm from baseline
what do we mean by a ‘reactive CTG’?
normal variability is demonstrated
what must we do if there are signs of fetal respiratory distress + hypoxia during labour?
emergency C-section
what are the 4 types of decelerations on a CTG?
early and late decelerations
variable and prolonged decelerations
what do late decelerations indicate on a CTG?
what exactly is a late deceleration?
what must we do?
Late decelerations begin at the peak of uterine contraction and recover after the contraction ends.
This type of deceleration indicates there is insufficient blood flow through the uterus and placenta.
As a result blood flow to the foetus is significantly reduced causing foetal hypoxia and acidosis.
If we see this we must take a fetal scalp lactate. If abnormal i.e. > 4.8, then emergency c-section is required
what is a cause of variable decelerations on CTG?
umbilical cord compression
what are some features of CTG which may indicate SEVERE VARIABLE DECELERATION indicating fetal hypoxia?
Deep and wide- >60bpm and >60secs or Delayed recovery or rebound tachycardia
what are the possible causes of prolonged deceleration on CTG?
sustained hypoxia causing sustained bradycardia can be due to:
cord compression
maternal hypotension
sustained uterine contraction
placental abruption
In the antenatal period you notice that the CTG is non-reactive. what do you want to do to ix further?
doppler ultrasound looking for uterine artery waveforms!
what might you do if you notice the CTG has absent variability, sinusoidal pattern and late deceleration?
emergency C section if baby is > 24 weeks gestation and viable
in the intrapartum period you notice that the CTG is grossly abnormal and indicating foetal hypoxia. what should you do?
Deliver the baby!
If the cervix is fully dilated and the head is low and engaged in vaginal canal–> suction/vacuum or forceps
if NOT, then emergency C-SECTION
what are the two components of a CTG?
the top part indicates the baseline fetal HR and variability
the bottom part of the CTG ‘toco’ is the contractions of the uterus
what are the normal values for baseline HR on a CTG?
110-160bpm
how do we determine the baseline HR on a CTG?
look at the trace between uterine contractions to determine baseline HR
The baseline rate is the average heart rate of the foetus within a 10 minute window.
what might you think if you cannot see uterine contractions on a CTG?
antenatal CTG
What exactly do we mean by variability on a CTG? what are we looking for on the CTG?
determine the baseline fetal HR and look at the peaks and troughs of the trace. Usually peaks and troughs 5-25bpm around baseline. If less then 5bpm then we say it is absent or reduced variability
what must we do first if we get an indeterminate CTG instead of immediately sending the woman to theatre for a c-section?
Check whether the fetal HR recorded on the CTG or u/s is actually the fetus and not the maternal HR.
Do this by timing the maternal pulse or putting on a sat probe, and or placing a fetal scalp clip to more accurately check the fetal HR.
If still indeterminate and the baby is cephalic presentation, do a fetal scalp lactate. if > 4.8, send to theatre.
what is the normal acceleration rate on a CTG?
2 accelerations in 15 secs
decelerations during an antenatal trace is….?
abnormal!
what is the time period per square on a CTG?
small square= 30s
large square= 1min
if you see reduced variability on a CTG is it an emergency?
need to evaluate over 40mins.
If > 40mins reduced variability then CTG abnormal.
Consider your 4 SSSS
Sleeping
Sedated
Submature
Sick
on a ctg, what exactly do we mean by an acceleration? what are we looking at?
if the baseline fetal HR rapidly trends up then it is an acceleration generally
describe what we mean by an ‘early deceleration’?
deceleration that occurs DURING uterine contractions.
Increased vagal tone due to increased fetal ICP
this is physiological and resolves after the contraction ends.
what do we mean by a ‘variable deceleration’ and what must we do?
Variable decelerations are observed as a rapid fall in baseline rate with a variable recovery phase.
They are variable in their duration and may not have any relationship to uterine contractions.
Can indicate cord compression
We need to closely monitor the CTG.
Change the maternal position to see if it relieves the variable decelerations
what exactly do we mean by prolonged decelerations?
A deceleration that last more than 2 minutes.
If it lasts between 2-3 minutes it is classed as non-reassuring.
If it lasts longer than 3 minutes it is immediately classed as abnormal.
what are the antenatal indications for CTG during labour?
Abnormal antenatal CTG
- Abnormal Doppler umbilical artery velocimetry
- Suspected or confirmed intrauterine growth restriction
- Oligohydramnios or polyhydramnios
- Prolonged pregnancy >42 weeks gestation
- Multiple pregnancy
- Breech presentation
- Antepartum haemorrhage
- Prolonged rupture of membranes (>24 hours)
- Known fetal abnormality which requires monitoring
- Prior uterine scar / caesarean section
- Essential hypertension or pre-eclampsia
- Diabetes where medication is indicated or poorly controlled, or with fetal macrosomia
- Other current or previous obstetric or medical conditions which constitute a significant risk of fetal compromise e.g. cholestasis, isoimmunisation, substance abuse
- Decreased fetal movements
- Maternal age greater than or equal to 42
what are the intrapartum indications for CTG monitoring during labour?
Induction of labour with prostaglandin / oxytocin
Abnormal auscultation or CTG
- Oxytocin augmentation
- Regional analgesia e.g. epidural or spinal, paracervical block
- Abnormal vaginal bleeding in labour
- Maternal pyrexia greater than or equal to 38°C
- Meconium or blood stained liquor
- Absent liquor following amniotomy
- Active first stage of labour >12 hours (i.e. after diagnosis of labour)
- Active second stage (i.e. pushing) >1 hour where birth is not imminent
- Preterm labour less than 37 completed weeks
- Tachysystole (more than 5 active labour contractions in 10 minutes, without fetal heart rate changes)
- Uterine hypertonus (contractions lasting more than 2 minutes or occurring within 60s of each other, without fetal heart rate changes
- Uterine hyperstimulation (tachysystole/hypertonus with fetal heart rate changes).
