[37] Intrapartum Assessment of Fetal Wellbeing Flashcards
What is intra-partum fetal monitoring?
The monitoring used immediately preceding or during childbirth
What suggests the possibility of fetal hypoxia?
- Changes in fetal HR
- Meconium-stained liquor
Can changes in fetal HR and meconium-stained liquor occur in normal labour?
Yes
What might a reduction in fetal movements indicate?
Fetal jeopardy
What might cessation in fetal movements indicate?
Fetal death
What things can be used to assess fetal wellbeing?
- Meconium
- Intermittent auscultation
- Fetal cardiotocography
- Fetal scalp blood sampling
What is meconium?
A dark green liquid normally passed by a newborn baby
What does meconium contain?
- Mucus
- Bile
- Epithelial cells
What can sometimes happen with meconium?
It can be passed when the baby is still in the womb, staining the amniotic fluid
What variation is there in meconium in the liquor?
Can very from very light to heavy staining
When is meconium staining in the liquor considered significant?
If dark green or black, with thick, tenacious appearance
What is meconium stained liquor considered to be a sign of?
Fetal distress
What is the problem with passing meconium whilst still in utero?
Components of the meconium, especially bile salts and enzymes, can cause serious complications if they are inhaled by the fetus at any stage of labour
What can be caused by inhalation of meconium by the baby?
Meconium aspiration syndrome
What pathological mechanisms participate in meconium aspiration syndrome?
- Airway obstruction
- Surfactant dysfunction
- Inflammation
- Lung oedema
- Pulmonary vasoconstriction
- Bronchoconstriction
What % of infants in the developed world are born with meconium-stained liquor?
8-25%
What % of live births does meconium aspiration syndrome occur in?
1-3%
What are the risk factors for passing meconium in utero?
- Placental insufficiency
- Maternal hypertension and pre-eclampsia
- Oligohydraminos
- Smoking
- Cocaine abuse
- Increased maternal age
What should be done if significant meconium staining is noted in labour?
Should be continuous electrical fetal monitoring
What should be done if there is significant meconium staining noted in labour, and signs of fetal distress?
A fetal blood sample should be obtained
What should be done at delivery if there is meconium stained liquor, and the neonate is in good condition?
There should be no suction, and the baby should be observed for signs of respiratory distress in the first hour of life, the second hour of life, and then 2 hourly until 12 hours old
How is it defined that the fetus is in good condition at delivery?
Apgar score >5
What should be done at delivery if there is blood or any lumps of meconium in the oropharynx?
Suction should be used in the upper airways
What should be done at delivery if there is meconium stained liquor, and the neonate is unwell?
Follow guidelines for meconium aspiration
What is intermittent auscultation used for?
Monitoring of FHR
How often should FHR be monitored in the first stage of labour?
Every 15 minutes for a period of 1 minute
When should the FHR be checked in the first stage of labour?
Soon after a contraction
How is intermittent auscultation of FHR performed?
Using a handheld Doppler ultrasound transducer or Pinard fetal stethoscope
How often is the FHR monitored during the second stage of labour?
Every 5 minutes, or every other contractions
How are contractions monitored in labour?
By manual palpation over a period of 10 minutes
What can manual palpation of contractions over a period of 10 minutes determine?
Frequency and duration
What can the indications for the use of continuous electrical fetal monitoring be divided into?
- Maternal
- Fetal
What are the maternal indications for the use of continuous electrical fetal monitoring?
- Previous C-section
- Pre-eclampsia
- Post-term pregnancy
- Prolonged rupture of membranes
- Induced labour
- Diabetes
- Antepartum haemorrhage
- Other maternal medical disease
What are the fetal indications for the use of continuous electrical fetal monitoring?
- Fetal growth restriction
- Prematurity
- Oligohydraminos
- Abnormal Doppler artery velocimetry
- Multiple pregnancy
- Meconium-stained liquor
- Breech presentation
What does cardiotocography enable?
Continuous monitoring of the fetal HR, and the frequency and duration of uterine contractions
How is the FHR determined in CTG?
Usually using a Doppler ultrasound transducer
Where is the Doppler ultrasound transducer placed for CTG monitoring?
Applied externally to maternal abdomen
How is uterine activity usually recorded for CTG monitoring?
Using a pressure transducer
Where is the pressure transducer applied for CTG monitoring?
Over the anterior abdominal wall, between the fundus and the umbilicus
Other than using a pressure transducer, how can uterine activity be measured?
By inserting a fluid-filled catheter or pressure sensor into the uterine cavity through the cervical canal
What is the advantage of external tocography?
It gives an accurate measurement of the frequency and duration
What is the limitation of external tocography?
It only gives relative information of intrauterine pressure
What does accurate measurements of intrauterine pressure require?
Intrauterine catheter or transducer
Why are intrauterine catheters and transducers not routinely used to measure uterine pressure in most centres?
Lack of evidence about clinical benefit
What is the normal FHR?
100-160 BPM
What is meant by baseline variability?
The FHR exhibits variation from the baseline lol
What does baseline variability record?
Oscillations of the heart rate around the baseline heart rate
How much is baseline variability?
5-25bpm
When is baseline variability reduced physiologically?
During the fetal sleep phase
When can baseline variability be reduced pathologically?
- Hypoxia
- Infection
- Medication
What is classified as an abnormal baseline variability?
Variability >5bpm for >90 minutes
What might an abnormal baseline variability indicate?
Fetal jeopardy
What are accelerations defined as?
Transient, abrupt increases in heart rate of more than 15 bpm for more than 15 seconds
What are accelerations associated with?
Fetal movements
What are accelerations a reflection of?
Activity of the somatic nervous system
What are accelerations a sign of?
Reassuring sign of good fetal health
What are decelerations defined as?
A decrease in heart rate of more than 15bpm for more than 15 seconds
What defines the different patterns of decelerations?
Their relationship to uterine contractions and their intensity
What are early decelerations synchronous with?
Uterine contraction
When does the nadir (lowest point) occur with early decelerations?
At the peak of the contraction
How much does the HR decrease in early decelerations?
Generally less than 40 bpm
What are early decelerations due to?
Generally due to head compression
Are early decelerations considered to be physiological?
Yes
When are early decelerations seen?
In the late first and second stage of labour
Describe late decelerations
The onset of slowing of HR occurs well after the contraction is established, and does not return to normal baseline rate until at least 20 seconds after the contraction is completed
What are late decelerations due to?
Placental insufficiency
What might late decelerations be indicative of?
Fetal hypoxia
When might late decelerations be indicative of fetal hypoxia?
When accompanied by a rise in the baseline rate and reduction in baseline variability
In what respects do variable decelerations variable?
Timing and amplitude
Describe variable decelerations
They have a initial slight transitory rise in the baseline rate, followed by a precipitous fall followed by quick recovery to the baseline and slightly beyond
How much does the heart rate fall by with variable decelerations?
Usually at least 40BPM
What causes variable decelerations?
Cord compression
What is the result of variable decelerations being caused by cord compression?
It varies with each contraction, giving rise to variable shapes, sizes, and timings of decelerations
What are variable decelerations considered to be?
Non-reassuring features in a CTG trace
What features of variable decelerations suggest worsening hypoxia?
- Increase in depth and duration of decelerations
- Rise in baseline rate
- Reduction in baseline variability
What are atypical variable decelerations?
Additional changes to simple variable decelerations in the form of slow recovery to baseline rate or a combined variable followed immediately by late decelerations
What are atypical variable decelerations considered to be?
Abnormal features
What can FHR trace features be classified into?
- Reassuring
- Non-reassuring
- Abnormal
What is the classification of FHR traces based on?
The classification of the features found on it
What can FHR traces be classified as overall?
- Normal
- Suspicious
- Pathological
What are reassuring features on FHR trace?
- Baseline 110-160bpm
- Variability 5 or more bpm
- No decelerations
- Accelerations present
What are non-reassuring features on FHR trace?
- 100-109 or 161-180 bpm
- Variability <5 for 40-90 minutes
- Typical variable decelerations with over 50% of contractions, occuring for over 90 minutes, or simple prolonged deceleration for up to 3 minutes
What are abnormal features on FHR trace?
- <100 or >180 bpm, or sinusoidal pattern
- Variability of <5 for 90 minutes
- Atypical variable decelerations with over 50% of contractions or late decelerations, both for over 30 minutes, or single prolonged deceleration for more than 3 minutes
What is classified as a normal FHR trace?
All features are classified as reassuring
What should be done when a normal FHR is determined?
Continue intermittent or continuous monitoring, as indicated by risk factors
What is classified as a suspicious FHR trace?
FHR trace with one feature classified as non-reassuring, and the remaining as reassuring
What should you do when a suspicious FHR trace is determined?
- Exclude factors indicating the need for immediate delivery
- Treat dehydration, hyperstimulation, hypotension, and change position
- Continue CTG
What things that would require immediate delivery should be excluded when there is a suspicious FHR trace?
- Cord prolapse
- Uterine rupture
- Abruption
What is classified as a pathological FHR trace?
FHR trace with two or more features classified as non-reassuring, or one or more classified as abnormal
What should you do when a pathological FHR trace is found?
- Exclude factors indicating need for immediate delivery
- Treat dehydration or hyperstimulation
- Change position
- Deliver if prolonged bradycardia
- Either obtain further information on fetal status by fetal blood scalp sampling, or deliver
What is fetal scalp blood sampling?
When fetal blood is obtained directly from the scalp through an amnioscope
When is fetal scalp blood sampling used?
When abnormalities of fetal heart rate occur in labour
What is the purpose of fetal scalp blood sampling?
To determine fetal acid-base balance
How should a sample be obtained for fetal scalp blood sampling?
The amnioscope is inserted through the cervix, which must be dilated to at least 2cm. The mother lies in the left lateral position. A small stab incision is made in the fetal scalp, and blood is collected into a heparinised capillary tube
Why should the mother lie in left lateral position when obtaining a sample for fetal scalp bloood sampling?
To avoid the risk of inducing supine hypotension
How is the sample collected for fetal scalp blood sampling analysed?
In a blood gas analyser
What is the normal pH of fetal blood?
7.25-7.35
What does the management of abnormal fetal blood pH depend on?
The degree of abnormality
What does a fetal blood pH of 7.2-7.25 in the first stage of labour indicate?
Mild acidosis
How should a fetus with mild acidosis be managed?
Sampling should be repeated within the next 30 minutes
How should a fetal blood pH of <7.2 be managed?
Delivery is recommended, unless spontaneous delivery is imminent
What should be done if there is a sufficient sample of fetal blood?
A full blood gas analysis
Why should a full blood gas analysis be performed if there is sufficient sample of fetal blood?
Because a raised pCO2 with normal base excess may indicate respiratory acidosis
Why is it important to know if the fetus has respiratory acidosis?
It may correct itself if the posture of the mother is changed
