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Assessment of foetal well-being (Foetal heart rate (Deceleration (Early…
Assessment of foetal well-being
methods
Electronic monitoring Cardiotocography (CTG):
OCT – oxytocin challenge test ,
NST – NON-Stress test,
BIOPHYSICAL PROFILE (Manning TEST) ,
Ultrasonography (Doppler) , Pulse-oximetry, Gasometry, Foetal ecg
Foetal heart rate
! 110-150 heart beats per minute – normocardia
! >150 heart beats per minute – tachycardia
! <110 heart beats per minute – bradycardia
Reasons of bradycardia:
1.hypoxaemiain a fetus caused by
maternal hypotension or hypoxia (IVC syndrome)
utero-placental insufficiency (strong uterine contractions or placental abruptio)
2.pressure on foetal head
3.Foetal haemmorhgage (for example damage in vasa previa)
4.Decline in foetal compensation abilities in cases of hypoxia and acidosis (terminal bradycardia)
5.Disturbancies in umbilical flow (prolapsus or compression)
Reasons for chronic bradycaria:
A-V block
Medications
Hypothermia
Idiopatic
Reasons for tachycardia:
Infections,
Medications – beta-agonists and atropine,
hypoxia accompanied by late decelerations
Foetal immaturity (20 weeks – 155 beats/min., 30 weeks – 144 beats/min.)
drugs, smoking, maternal hyperactivity
Variability:
Short-term changes in foetal heart rate are called Variability.
types:
silent – 0-5 heart beats per minute
narrow – 5-10 heart beats per minute
Normal (the correct one) – 10-25 heart beats per minute
Increased - >25 heart beats per minute
Sinusoidal – 5-30 beats/min, frequency 2-5 /min
Normal, reassuring CTG – all types of variability except sinusoidal, lasting 40-60 minutes (periods of different fetal activity)
Prolonged increased avriability – fetal asphyxia (umbilical circulation disturbancies) or CNS stimulation
Reduced variability – fetal sleep, prolonged asphyxia, immaturity, heart conducting system malformations, malformations of cerebral cortex.
Sinusoidal pattern – severe asphyxia, anemia – lethal pattern
Accelration
Temporary increase in foetal heart rate of 15 heart beats per minute or more as compared with basic foetal heart rate. lasts for 15 seconds or more.
Usually related to the fetal movements
Sponatneous
Periodic (related to the uterine contractions)
Induced (external stimulation)
Compensational (after deceleration)
Deceleration
Temporary decrease in foetal heart rate of 15 heart beats per minute or more as compared with basic foetal heart rate. lasts for 15 seconds or more.
Early – the lowest heart rate at the top of the contraction.
Late – the lowest heart rate at the end of after contraction
Variable – no correlation with uterine contractions
Early decelerations
increased intracranial pressue and stimulation of sympathetic system (Gauss syndrome – deceleration at the time or after the fetal head reaches pelvic floor)
They do not signal fetal danger. May be the result of feto-maternal disproportion or excessive contractility of the uterus.
Late decelerations
start 10-30 seconds after beginning of the contraction
activation of chemoreceptors in aorta and vagus nerve by hypoxemia
result of utero-placental insufficiency
Poor prognosis with reduced variability, „depth” of deceleration and lack of compensational tachycardia (loss of adaptive mechanisms)
Variable decelerations
not related to the uterine contractiions, different shapes:
disturbancies in umbilical blood flow, fetal head compression,
may be not related to fetal asphyxia
Umbilical cord collision
The closing of the umbilical vein and decrease in foetal blood pressure,
Complete stop in umbilical circulation – sudden incrase in pressure,
Second decrease in blood pressure (umbilical arteries open up),
Umbilical circulation goes back to normal.
Signs of placental insufficiency
low foetal activity – decreased number of accelerations and narrow oscillations / silent – Hypoxia
CTG tests
NST (Non Stress Test)
Non-reactive – the test needs to be prolonged or repeated after one hour, if the reading is still non-reactive or if decelerations take place further foetal well-being monitoring needs to be started (OCT test, doppler ultrasonography)
30 minutes CTG reading plus foetal movement monitoring
Results:
The test is reactive when there are 2 or more accelerations during 30 minutes, normocardia, foetal movements are registered, oscillation is of more than >10 heart beats per minute.
The test is non reactive when: foetal movements and oscillation are not observed, oscillation is of less than <10 heart beats per minute.
The test is inconclusive if there is one acceleration plus foetal movements, lack of full acceleration criteria, oscillations are of less than <10 heat beats per minute, tachycardia/ bradycardia
Oxytocin challenge test (OCT)
foetal heart rate assessment during uterine contractions.
Intravenous oxytocin infusion.
The test is viewed as successful when there are 3 contractions within 10 minutes.
Contraindications to OCT
classical C-section before,
Placenta praevia,
Danger of premature labour
results:
negative – contractions are present, the oscillation is correct, no decelerations, reactive reading,
positive – late decelerations > 50% contractions,
inconclusive – late decelerations < 50% contractions ,
failed – no contractions.
Foetal biophysical profile – Manning test
30 minutes observation of foetal activity in real time with the use of ultrasonography together with conducting an NST.
Assessed parametres:
muscle tone
foetal movements
foetal breathing movements
amniotic fluid volume
Foetal pulse-oximetry
Results:
SpO2 > 30% foetal oxygenation within norm
SpO2 ~ 30% borderline, intensive CTG monitoring
SpO2 < 30% foetal well-being needs to be verified with the use of gasometry or the labour must be ended
Cardiotocography
Simultaneous assessment of:
fetal heart rate, uterine contractions , fetal movements.