Fetal Assessment

Question 1

Broadly speaking, what is CTG used to screen for?

Answer 1

Fetal hypoxia

Question 2

What does a CTG include?

Answer 2

• Stretch gauge for maternal contractions

- USS + Doppler for fetal heartbeat

Question 3

What are the 4 important features on CTG?

Answer 3

• Heart rate
• Baseline variability
• Accelerations (an increase of 15+ bpm for at least 15 seconds)
• Decelerations (a decrease of 15+ bpm for at least 15 seconds)

Question 4

What are the normal parameters of a CTG?

Answer 4

1. Heart rate: 110-150 bpm at term
2. Variability: >=10 bpm from baseline
3. Accelerations: 2+ over 20-30minute CTG
4. Decelerations: none.

Question 5

What would be a reassuring CTG?

Answer 5

Heart rate of 110-150 bpm, with good variability, presence of accelerations and absence of decelerations

Question 6

What is the ‘biophysical profile’? How is it calculated and what is good/bad?

Answer 6

A score based on a collection of factors that indicate fetal wellbeing, can be used to identify hypoxia
Includes:
1) Fetal breathing movements: want 30+ in 30 mins
2) Fetal body movements: want 3+ in 30 mins
3) Fetal tone: limb flexures are good
4) CTG: reactive (accelerations) are good
5) Amniotic fluid volume: deep large pocket is good
If each category is positive, it scores a 2. If not- 0. Total score is 0-10.
0-4 abnormal. 6- repeat. 8-10 good.

Question 7

T/F. Herniation of the abdominal contents into the umbilicus is normal in the fetus

Answer 7

True. This is normal in fetuses 5/6-12 weeks gestation. After that time, this is called exomphalos and indicates possible chromosomal abnormalities

Question 8

Atresias of the upper GI tract may lead to….

Answer 8

Polyhydramnios as the baby is unable to swallow amniotic fluid

Question 9

Renal agenesis may lead to…

Answer 9

Oligohydramnios as the baby does not produce urine, which contributes to amniotic fluid volume. This can then cause pulmonary hypoplasia, in a condition called Potter’s syndrome

Question 10

Fetal RBCs are produced by the….

The main type of blood is…

Answer 10

Liver, then the bone marrow later one.

HbF, then HbA by the end of gestation

Question 11

Flow in which artery is indicative of placental function? Explain.

Answer 11

Umbilical artery

-Flow through the umbilical artery (from baby to placenta) is dependent on the resistance in the placenta

Question 12

Name some causes of a fetal tachycardia.

Answer 12

• Fetal hypoxia
• Infection
• Fetal anaemia
• Fetal hyperthyroidism
• Drugs (ritodrine)

Question 13

What can affect the flow in the umbilical artery?

Answer 13

• Placental changes

- Decreased flow could be due to placental disease eg. pre-eclampsia with significant placental dysfunction

Question 14

How is the umbilical artery assessed using Doppler USS? What would you see in placental dysfunction?

Answer 14

Assessing the end diastolic flow and the pulsatility index/resistance index

• In a diseased placenta, there may be reduced, absent or in the worst case- reversed end diastolic flow (blood goes back to the fetus during diastole)
• There will also be a high pulsatility/resistance index, which means there is a high degree of resistance in the placenta (high resistance = low flow)

Question 15

Flow in which artery is indicative of fetal hypoxia? Explain.

Answer 15

The fetal vessels, such as the middle cerebral artery and the aorta.

• When the fetus is hypoxic, blood flow is preferentially directed to the most important organs eg. brain
• This is called cerebral distribution
• As a result, the flow in the MCA will be high, while it may be low in the aorta

Question 16

What can affect flow in the fetal vessels?

Answer 16

• Fetal hypoxia

- Severe fetal anaemia

Question 17

What findings would you see on Doppler USS in a fetus with severe anaemia?

Answer 17

• Increased flow in the fetal MCA, with decreased pulsatility/resistance index
• If very severe, decreased flow in the aorta, with increased pulsatility/resistance index

Question 18

Fetal acidaemia is suggested by what finding on Doppler USS?

Answer 18

• Absent end diastolic flow in the aorta

- Most sensitive: increasing pulsatility index in the central veins supplying the heart (IVC, ductus venosus)

Question 19

What findings would you see on Doppler USS in a fetus with cardiac compromise due to hypoxia?

Answer 19

• Reduced a wave in the ductus venosus

- OR retrograde a wave in the ductus venosus

Question 20

Flow in which artery is predictive of pre-eclampsia? Explain.

Answer 20

Maternal uterine artery

-Increased resistance in pre-eclampsia indicating abnormal placentation

Question 21

At the 20 week anomaly scan, there is increased resistance in the maternal uterine artery. Does this need monitoring? Why/why not?

Answer 21

• Yes, this should be monitored as there is a risk of progression to pre-eclampsia
• Monitor fetal growth, hypertension and proteinuria

Question 22

What is the cerebroplacental ratio? What does it reflect?

Answer 22

• The ratio of the pulsatility/resistance index in the MCA:umbilical artery
• Abnormal ratios indicate increased likelihood of perinatal death and adverse outcomes