How to read a CTG - GM

Question 1

what is cardiotocography

Answer 1

used to monitor fetal HR and uterine contractions
most commonly used in the third trimester

Question 2

the two transducers of CTG

Answer 2

one record fetal HR using US
the other monitors contractions of the uterus by measuring tension of the maternal abdominal wall (providing an indirect indication of intrauterine pressure)

Question 3

DR C BRAVADO

Answer 3

DR - define risk
C - contractions
BRa - baseline rate
V - variability
A - accelerations
D - decelerations
O - overall impression

Question 4

risk factors that may influence interpretation of a CTG

Answer 4

gestational diabetes
hypertension
asthma
multiple gestation
post date gestation
previous CS
intrauterine growth restriction
premature rupture of membranes
congenital malformations
oxytocin induction/augmentation of labour
pre-eclampsia
absense of prenatal care
smoking
drug abuse

Question 5

contractions

Answer 5

• record number of contractions in a 10 minute period
  individual contractions are seen as peaks on the uterine activity monitor
  each big square is equal to 1 minute

Question 6

baseline rate of foetal heart

Answer 6

average HR of the fetus in a 10-minute window
ignore accelerations or decelerations

Question 7

normal baseline foetal heart rate

Answer 7

110-160 bpm

Question 8

fetal tahcycardia

Answer 8

baseline HR greater than 160
causes include
- fetal hypoxia
- chorioamnionitis
- hyperthyroidsim
- fetal or maternal anaemia
- fetal tachyarrythmia

Question 9

fetal bradycardia

Answer 9

baseline HR less than 110

Question 10

when might fetal bradycardia be normal

Answer 10

it is common to have a baseline HR of 100-120 during
- postdate gestation
- occipul posterior or transverse presentations

Question 11

severe prolonged tachycardia

Answer 11

less than 80 bpm for more than 3 minutes
indicates severe hypoxia
causes include
- prolonged cord compression
- cord prolapse
- epidural and spinal anaesthesia
- maternal seixures
- rapid fetal descent

Question 12

variability

Answer 12

variation in fetal HR from one beat to the next
a healthy fetus will constantly be adapting its heart rate in response to changes in its environment

Question 13

normal level of variability

Answer 13

5-25 bpm
indicates intact neurological system in the fetus

Question 14

categories of variability

Answer 14

reassuring, non-reassuring, abnormal

Question 15

non reassuring variability

Answer 15

less than 5 bpm for between 30-50 minutes
more than 25 bpm for 15-25 minutes

Question 16

abnormal variability

Answer 16

less than 5bpm for more than 50 minutes
more than 25 bpm for more than 25 minutes
sinusoidal

Question 17

causes of reduced variability

Answer 17

fetal sleeping: most common cause, should last no longer than 40 minutes
fetal acidosis (due to hypoxia): more likley if late decelerations are also present
fetal tachycardia
drugs: opiates, benzodiazepines, methyldopa, and magnesium sulphate
prematurity: variability is lower at earlier gestations (< 28 weeks)
congenital heart abnormalities

Question 18

accelerations

Answer 18

an abrupt increase in baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds
presence of accelerations is reassuring
accelerations occuring alongside uterine contractions is a sign of a healthy fetus

Question 19

absent accelerations

Answer 19

with an otherwise normal CTG, this is of uncertain significance

Question 20

decelerations

Answer 20

abrupt decrease in a baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds

Question 21

cause of decelerations

Answer 21

in response to hypoxic stress, the fetus reduces its heart rate to preserve myocardial oxygenation and perfusion.
unlike an adult, a fetus cannot increase its respiration depth and rate

Question 22

types of decelerations

Answer 22

early deceleration
variable deceleration
late deceleration
prolonged deceleration
sinusoidal pattern

Question 23

early decelerations

Answer 23

start when uterine contractions begin and stop when uterine contractions stop
considered physiological

Question 24

are early decelerations pathological

Answer 24

they are physiological and not pathological

Question 25

why do early decelerations occur

Answer 25

due to increased fetal intracranial pressure caused increased vagal tone will quickly resolve once the contraction ends and intracranial pressure reduces

Question 26

variable deceleration

Answer 26

rapid fall in baseline fetal heart rate with a variable recovery phase may not have any relationship to uterine contractions

Question 27

variable decelerations are seen in

Answer 27

often seen during labour and in pateints with reduced amniotic fluid volume

Question 28

what causes variable deceleration

Answer 28

umbilical cord compression initially there is compression on the umbilical vein which causes acceleration, the compression on the umbilical artery which causes deceleration, then pressure on the cord is reduced causing another acceleration

Question 29

shoulders of deceleration

Answer 29

the accelerations that occur before and after a variable deceleration indicate that the fetus is not yet hypoxic and is ada[ting to the reduced blood flow

Question 30

variable decelerations without shoulders

Answer 30

more worrying as it suggests the fetus is hypoxic

Question 31

late deceleration

Answer 31

begin at the peak of uterine contraction and recover after the contraction ends

Question 32

are late decelerations worrying

Answer 32

yes indicates there is insufficient blood flow to the uterus and placenta blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis

Question 33

causes of reduced uteroplacental blood flow include

Answer 33

maternal hypotension pre-eclampsia uterine hyperstimulation

Question 34

prolonged deceleration

Answer 34

deceleration that lasts more than 2 minutes

Question 35

non-reasurraing deceleration

Answer 35

between 2-3 minutes

Question 36

abnormal deceleration

Answer 36

longer than 3 minutes

Question 37

sinusoidal pattern

Answer 37

sinusoidal CTG pattern is rare very concerning, associated with high rates of fetal morbidity and mortality

Question 38

characteristics of a sinusoidal CTG pattern

Answer 38

- a smooth, regular, wave like pattern - frequency of around 2-5 cycles a minute - stable baseline rate around 120-160bpm - no beat to beat variability

Question 39

a sinusoidal CTG pattern usually indicates

Answer 39

severe fetal hypoxia severe fetal anaemia fetal/maternal heamorrhage

Question 40

what qualitites should a reassuring CTG have

Answer 40

baseline fetal heart rate: 110-160bpm baseline variability: 5-25bpm decelerations: none or early, variable decelerations with no concerning characteristic for less than 90 minutes