Flashcards in Assessment of Foetal Wellbeing Deck (35)
What are the US parameters used in foetal surveillance?
What is foetal biometry?
Involves absolute and serial measurements.
What is the amniotic fluid index?
Sum of the vertical depth of amniotic fluid in each of the four quadrants.
What are the components of foetal activity assessed on US?
What is the biophysical profile of the foetus on US?
5 parameters, 2 points each. 8/10+ = reassuring
-Amniotic fluid index
What is assessed on doppler US?
-Umbilical artery (waveform)
What is the significance of the umbilical artery waveform?
-Raised SDR, absent EDF, then reversed EDF a/w
-progressive deterioration in placental gas exchange
-evidenced by stepwise increase in perinatal mortality
Normal CTG baseline?
Normal CTG variability?
Normal CTG accelerations?
15bpm for 15s
Normal CTG decelerations?
No ominous decelerations
What are the abnormal CTG variability patterns?
-INCREASED (>25bpm): hypoxia
-REDUCED (3-5bpm): sick (hypoxia), sleeping, sedated, submature (SSSS)
Causes of sedation as detected by non-reactive, reduced variability CTG?
What are the characteristics of early decelerations?
– Timing: simultaneous with contraction, uniform, repetitive
– Shape: Gradual onset and recovery
– Depth: Almost invariably shallow
– Cause: Head compression
Receptor associated with early decelerations?
What are the characteristics of late decelerations?
– Timing: Uniform, repetitive, begin after contraction onset, recover after contraction complete
– Shape: Gradual onset and recovery
– Depth: May be deep or almost imperceptively shallow
– Cause: Hypoxia
What are the characteristics of variable decelerations?
– Timing: Variable, but usually simultaneous with contraction, repetitive or intermittent
– Shape: Sudden onset and recovery
– Depth: Mild (<60bpm for <60 secs), Mod (>60bpm OR >60 secs), Severe (> 60bpm AND >60 secs)
– Cause: Cord compression
How are variable decelerations classified?
60 bpm OR > 60 secs
> 60 bpm AND > 60 secs
What are the characteristics of prolonged decelerations?
-Shape: sustained bradycardia
-Timing: more than 2 mins
-Cause: sustained hypoxia
what are causes of sudden severe foetal hypoxia?
-Sustained uterine contraction
How are antenatal CTGs classified and what is the implication of each?
-Reactive: (reassured). Normal baseline, normal variability, accelerations, no adverse decelerations.
-Non-reactive (investigate). No accelerations, reduced variability.
-Critical (DELIVER - C/S). Late decelerations, absent variability, sinusoidal pattern.
How to investigate antenatal non reactive CTG?
Is it due to hypoxia??
-Foetal stimulation tests e.g. VAST
-Doppler US (UA waveform, MCA PSV)
Characteristics of the gynaecoid pelvis?
Classic female pelvis.
-Posterior sagittal diameter of inlet only slightly shorter than anterior sagittal diameter
-posterior pelvis rounded and wide
-spines not prominent
What is mentum presentation?
Face presentation with foetal head hyperextended so occiput in contact with foetal back; chin (mentum) presenting.
What are the types of cephalic presentations?
-face (mentum / chin point of reference)
Why is incision in caesarean made in lower uterine segment?
Risk of uterine rupture; lower uterine segment does not actively contract during labour
What is the risk of uterine rupture in VBAC after one prior caesarean?
1 in 200
How does foetal umbilical artery Doppler US waveform change with increased gestation?
With increased gestation there is an increase in end diastolic flow velocity relative to peak systolic velocity causing increased S/D ratio.
What is associated with increased S/D ratio?
Increased resistance in placental vascular bed.