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Year 5 - Obstetrics and Gynaecology > Foetal procedures (incl. CTG, growth scans, dopplers) > Flashcards

Foetal procedures (incl. CTG, growth scans, dopplers) Flashcards

1
Q

What is the 3-6-9-12-15 rule for fetal bradycardia?

A
  • 3min - emergency bell pressed
  • 6min - change position and examine
  • 9min - decision to go to theatre
  • 12min - ready for C-section
  • 15min - deliver baby
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2
Q

What is a CTG?

A

Cardiotocography (CTG) is used during pregnancy to monitor fetal heart rate and uterine contractions.

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3
Q

How does the CTG work?

A

Involves the placement of two transducers onto the abdomen of a pregnant woman.

One transducer records the fetal heart rate using ultrasound and the other transducer monitors the contractions of the uterus by measuring the tension of the maternal abdominal wall (providing an indirect indication of intrauterine pressure).

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4
Q

What is the acronym used to read a CTG?

A
  • DR: Define risk
  • C: Contractions
  • BRa: Baseline rate
  • V: Variability
  • A: Accelerations
  • D: Decelerations
  • O: Overall impression
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5
Q

What are some risks important to define when doing a CTG? Why is this useful?

A

High risk pregnancies include those with the following RFs. If these are present you may have a lower threshold for intervention.

Maternal medical illness

  • Gestational diabetes
  • Hypertension
  • Asthma

Obstetric complications

  • Multiple gestation
  • Post-date gestation
  • Previous cesarean section
  • Intrauterine growth restriction
  • Premature rupture of membranes
  • Congenital malformations
  • Oxytocin induction/augmentation of labour
  • Pre-eclampsia

Other risk factors

  • Absence of prenatal care
  • Smoking
  • Drug abuse
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6
Q

How do you record contractions?

A
  • How many are present in a 10 min period e.g. “2 in 10”
  • Duration of contractions - 1big square is 1min
  • Intensity by palpation
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7
Q

Assess uterine contractions on this CTG.

A

2 in 10

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8
Q

How do you assess baseline HR?

A

Assess average HR ver the last 10 minutes, ignoring any accelerations or decelerations.

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9
Q

What is the normal FHR?

A

A normal fetal heart rate is between 110-160 bpm.

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10
Q

What is the baseline FHR here?

A

~120bpm

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11
Q

Define fetal tachycardia.

A

Fetal tachycardia is defined as a baseline heart rate greater than 160 bpm.

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12
Q

List 5 casues of fetal tachycardia.

A

Causes of fetal tachycardia include:

  • Fetal hypoxia
  • Chorioamnionitis
  • Hyperthyroidism
  • Fetal or maternal anaemia
  • Fetal tachyarrhythmia
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13
Q

Define fetal bradycardia and severe prolonged bradycardia.

A

Fetal bradycardia = is defined as a baseline heart rate of <100 bpm.

Severe prolonged bradycardia = less than 80 bpm for more than 3 minutes);indicates severe hypoxia.

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14
Q

When is it common to have a FHR of between 100-120bpm?

A
  • Postdate gestation
  • Occiput posterior or transverse presentations
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15
Q

What are the causes of prolonged severe bradycardia?

A

Causes of prolonged severe bradycardia include:

  • Prolonged cord compression
  • Cord prolapse
  • Epidural and spinal anaesthesia
  • Maternal seizures
  • Rapid fetal descent
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16
Q

What are the causes of prolonged severe bradycardia?

A
  • Prolonged cord compression
  • Cord prolapse
  • Epidural and spinal anaesthesia
  • Maternal seizures
  • Rapid fetal descent
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17
Q

What is baseline variability? Why does it occur?

A

Baseline variability refers to the variation of fetal heart rate from one beat to the next.

Variability occurs as a result of the interaction between the nervous system, chemoreceptors, baroreceptors and cardiac responsiveness.

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18
Q

What is normal variability? What does it indicate?

A

Normal variability is between 5-25 bpm.

It is a good indicator of how healthy a fetus is, as a healthy fetus will constantly be adapting its heart rate in response to changes in its environment.

Normal variability indicates an intact neurological system in the fetus.

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19
Q

How do you calculate variability?

A

Assess how much the peaks and troughs of the heart rate deviate from the baseline rate (in bpm).

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20
Q

What are the 3 categories that variability is classified into?

A
  • Reassuring - 5-25bpm
  • Non-reassuring
  • Abnormal.
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21
Q

What is non-reassuring variability?

A

Non-reassuring:

  • less than 5 bpm for between 30-50 minutes
  • more than 25 bpm for 15-25 minutes
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22
Q

What is abnormal variability?

A
  • less than 5 bpm for more than 50 minutes
  • more than 25 bpm for more than 25 minutes
  • sinusoidal
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23
Q

Assess the variability on this CTG.

A

Normal - 10-25bpm variability

24
Q

List 5 causes of reduced variability on a CTG.

A
  • Fetal sleeping: this should last no longer than 40 minutes (this is the most common cause)
  • Prematurity: variability is reduced at earlier gestation (<28 weeks)
  • Drugs: opiates, benzodiazepines, methyldopa and magnesium sulphate
  • Fetal acidosis (due to hypoxia): more likely if late decelerations are also present
  • Fetal tachycardia
  • Congenital heart abnormalities
25
Q

Define acceleration on CTG.

A

Accelerations are an abrupt increase in the baseline fetal heart rate of greater than 15 bpm for greater than 15 seconds.

26
Q

What is the significance of accelerations? Is it abnormal to have no accelerations?

A

The presence of accelerations is reassuring- accelerations occurring alongside uterine contractions is a sign of a healthy fetus.

The absence of accelerations with an otherwise normal CTG is of uncertain significance.

27
Q

Define deceleration on CTG.

A

Decelerations are an abrupt decrease in the baseline FHR of greater than 15 bpm for greater than 15 seconds.

28
Q

What is the pathophysiology of decelerations on CTG?

A

Autonomic and somatic nervous system controm FHR. Hypoxic stress causes the fetus to reduce FHR to preserve myocardial oxygenation and perfusion, since (unlike adults) fetus cannot increase its respiration depth and rate.

29
Q

What are 3 types of decelerations?

A
  • Early deceleration
  • Variable deceleration
  • Late deceleration
  • Prolonged deceleration
30
Q

Define early deceleration. Is it physiological or pathological?

A

Early decelerations start when the uterine contraction begins and recover when uterine contraction stops.

Physiological

31
Q

What is the pathophysiology of early deceleration?

A

Due to increased fetal intracranial pressure causing increased vagal tone. It therefore quickly resolves once the uterine contraction ends and intracranial pressure reduces.

32
Q

What is shown? What is a cause?

A

Early deceleration - physiological due to increased fetal intracranial pressure causing increased vagal tone.

33
Q

Define variable deceleration. When are these usually seen?

A

Variable decelerations are observed as a rapid fall in baseline fetal heart rate with a variable recovery phase. Variable in their duration and may not have any relationship to uterine contractions.

Most often seen during labour and in patients’ with reduced amniotic fluid volume. Usually also caused by umbilical cord compression.

34
Q

What is the mechanims of variable deceleration in umbilical cord compression?

A

The mechanism is as follows:

  1. The umbilical vein is often occluded first causing an acceleration of the fetal heart rate in response.
  2. Then the umbilical artery is occluded causing a subsequent rapid deceleration.
  3. When pressure on the cord is reduced another acceleration occurs and then the baseline rate returns.
35
Q

What are the accelerations before and after a deceleration called?

A

shoulders of deceleration

36
Q

What do shoulders of deceleration indicate?

A

Indicates the fetus is not yet hypoxic and is adapting to the reduced blood flow. Variable decelerations can sometimes resolve if the mother changes position. The presence of persistent variable decelerations indicates the need for close monitoring.

Variable decelerations without the shoulders are more worrying, as it suggests the fetus is becoming hypoxic.

37
Q

What is shown? What is a cause?

A

Variable deceleration - umbilical cord compression, reduced amniotic fluid volume

38
Q

Define late deceleration.

A

Late decelerations begin at the peak of the uterine contraction and recover after the contraction ends.

39
Q

What is the pathophysiology of late decelerations?

A

This type of deceleration indicates there is insufficient blood flow to the uterus and placenta. As a result, blood flow to the fetus is significantly reduced causing fetal hypoxia and acidosis.

40
Q

What are the causes of reduced uteroplacental blood flow?

A
  • Maternal hypotension
  • Pre-eclampsia
  • Uterine hyperstimulation
41
Q

What is shown?

A

Late deceleration

42
Q

Define prolonged deceleration. When is it non-reassuring vs abnormal?

A

A prolonged deceleration is defined as a deceleration that lasts more than 2 minutes:

  • If it lasts between 2-3 minutes it is classed as non-reassuring.
  • If it lasts longer than 3 minutes it is immediately classed as abnormal.
43
Q

What is shown?

A

Prolonged deceleration

44
Q

What is this CTG pattern? What does it indicate?

A
  • Severe fetal hypoxia
  • Severe fetal anaemia
  • Fetal/maternal haemorrhage
45
Q

Define sinusoidal pattern CTG.

A

Rare, but very concerning as it is associated with high rates of fetal morbidity and mortality

A sinusoidal CTG pattern has the following characteristics:

  • 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
46
Q

What are the causes of sinusoidal pattern CTGs?

A

A sinusoidal pattern usually indicates one or more of the following:

  • Severe fetal hypoxia
  • Severe fetal anaemia
  • Fetal/maternal haemorrhage
47
Q

What are the CTG features classified as non-reassuring?

A
48
Q

What are the CTG features classified as abnormal/pathological?

A
49
Q

What is a biphasic shape deceleration?

A

W shape - no shoulders

50
Q

What information shoulf you have to reliably assess fetal growth?

A

Previous scans, at least 2 weeks apart, to determine rate of growth

Pattern of ‘smallness’ i.e. information about the AC and HC

Customisation of fetal growth charts to assess for constitutional non-pathological determinants of fetal growth

51
Q

List some indications for growth scanning.

A

Pre-conception:

  • BMI >35
  • Epilepsy (every 4 weeks from 28-36 weeks)
  • Diabetes (every 4 weeks from 28-36 weeks)
  • Chronic hypertension (every 4 weeks from 28-32 weeks)

Pregnancy related:

  • Gestational diabetes (every 4 weeks from 28-36 weeks)
  • Multiple pregnancy (from ~20 weeks gestation every 2-4 weeks depending on chorionicity and amnionicity)
  • Gestational hypertension (every 2-4 weeks)
  • Pre-eclampsia (every 2 weeks)
  • IUGR (every 2 weeks)
  • Placental abruption which settles (weekly)
52
Q

How is the growth measured on USS at different gestations?

A
  • Crown–rump length (CRL) is used up to 13 weeks + 6 days
  • Head circumference is used from 14 to 20 weeks’

Gestational age cannot be accurately calculated by ultrasound after 20 weeks’ gestation because of the wider range of normal values of AC and HC around the mean.

53
Q

How does the pattern of ‘smallness’ help identify the type of fetal growth?

A

Types of growth restriction :

  1. Symmetrical
  2. Asymmetrical - asymmetry between head measures (BPD, HC) and AC can be identified in:
    • FGR = where a brain-sparing effect will result in a relatively large HC compared with the A.
    • Diabetic pregnancy = where the abdomen is disproportionately large due to the effects of insulin on the fetal liver and fat stores.

NB: in normal growth restriction the abdomen (>30% reduction = FGR) will stop enlarging before the head which is ‘spared’.

54
Q

What does this pattern of growth restriction indicate?

A

Note that HC remains above 5th centile while the AC falls below 5th centile = case of _asymmetric FGR with
head sparing._

55
Q

What are some ‘at booking’ major risk factors for SGA?

A
  • Previous history of SGA or stillbirth
  • Heavy smoking
  • Cocaine usage
  • Heavy daily exercise
  • Maternal illness, e.g. diabetes
  • Parental SGA

Year 5 - Obstetrics and Gynaecology (87 decks)

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