interpreting CTG Flashcards
what is the acronym for CTG?
DR: Define risk C: Contractions BRa: Baseline rate V: Variability A: Accelerations D: Decelerations O: Overall impression
what are maternal factors that make a CTG high risk?
Gestational diabetes
Hypertension
Asthma
what are obstetric complications of that make a CTG high risk?
Multiple gestation Post-date gestation Previous cesarean section Intrauterine growth restriction Premature rupture of membranes Congenital malformations Oxytocin induction/augmentation of labour Pre-eclampsia
what is the base rate for fetal heart rate?
110-160 bpm
what is considered fetal tachycardia?
baseline heart rate >160
what are causes of fetal tachycardia?
- fetal hypoxia
- chorioamnionitis
- hyperthyroidism
- fetal or maternal anaemia
- fetal tachyarrhythmia
what is defined as fetal bradycardia?
- baseline heart rate of <100
which situations is it common to have baseline HR between 100-120 bpm?
- post-date gestation
- occiput posterior or transverse position
what values would be seen for severe bradycardia on CTG?
- 80bpm >3minutes
what are causes of prolonged severe bradycardia?
- prolonged cord compression
- cord prolapse
- epidural and spinal anasthaesia
- maternal seizures
- rapid fetal descent
what is reassuring baseline variability?
5-25 bpm
what is non reassuring baseline variability?
<5bpm for 30-50 mins
>25bpm for 15-25 minutes
what is abnormal variability?
<5bpm >50 mins
>25bpm >25 mins
sinusoidal
what is the most common cause of reduced variability in the CTG?
fetal sleeping-> no longer than 40 mins
what are worrying causes of reduced CTG variability?
- fetal acidosis due to hypoxia
- drugs: benzodiazepines, methyldopa and magnesium sulphate
- prematurity- variability is reduced at low gestational ages <28 weeks
- congenital heart abnormalities
what are decelerations?
> 15bpm decrease in heart rate >15 seconds
what is the cause of early decelerations?
they begin and recover with uterine contractions
and they are due to increased fetal intracranial pressure
they are physiological not pathological
what is the cause of variable decelerations?
- they don’t correlate to the uterine contractions often seen in patients with reduced amniotic fluid
- accelerations before and after the deceleration are called shouldering
- variable decelerations occur when the cord is compressed- umbilical vein occlusion causes the acceleration and artery occlusion causes the rapid deceleration
when is variable decelerations worrying?
if there is no shouldering it is worrying as the foetus can become hypoxic
what do late decelerations indicate?
there is insufficient blood flow to the uterus and the placenta
how do late decelerations appear on the CTG?
peak during uterine contraction and recover after the contraction
what are causes of reduced uropplacental blood flow causing late decelerations?
- maternal hypotension
- pre-eclampsia
- uterine hyperstimulation
what is considered a prolonged deceleration?
> 2 mins
> 3mins-> immediately classed as abnormal
a sinusoidal pattern is very concerning, what could it suggest?
Severe fetal hypoxia
Severe fetal anaemia
Fetal/maternal haemorrhage
