Fetal Circulation ✅

Question 1

How is oxygenated blood carried to the foetus?

Answer 1

Via the umbilical vein

Question 2

What organ does oxygenated blood in the umbilical vein bypass in foetal circulation?

Answer 2

The liver

Question 3

How does oxygenated blood bypass the liver?

Answer 3

Via the ductus venous

Question 4

Where does oxygenated blood travel after bypassing the liver?

Answer 4

The inferior vena cava

Question 5

Where does oxygenated blood pass after reaching the inferior vena cava?

Answer 5

Enters the right atrium

Question 6

What happens to oxygenated blood entering the right atrium?

Answer 6

It is shunted to the left atrium

Question 7

How is oxygenated blood shunted from the right atrium to left atrium?

Answer 7

Via the foramen ovale

Question 8

Where does oxygenated blood travel from the left atrium?

Answer 8

Into the left ventricle then aorta

Question 9

What does the aorta supply in the foetal circulation?

Answer 9

• Coronary arterys

- Cerebral vessels

Question 10

What is the result of the aorta supplying the coronary artery and cerebral vessels?

Answer 10

The foetal brain and heart get the most oxygenated blood

Question 11

How does deoxygenated blood from the cerebral and coronary vessels return to the heart?

Answer 11

Via the superior vena cava into the right atrium

Question 12

Where does deoxygenated blood pumped by the right ventricle go?

Answer 12

Some goes into the pulmonary artery, but the majority bypasses the lungs via the ductus arteriosus

Question 13

Where does blood bypassing the lungs via the ductus arteriosus go?

Answer 13

Into the aorta

Question 14

What happens to deoxygenated blood entering the aorta?

Answer 14

It it carried back to the placenta via two umbilical arteries

Question 15

What % of the combined ventricular output of the fetal heart passes into the lungs?

Answer 15

7%

Question 16

Which is the dominant ventricle in the fetal circulation?

Answer 16

Right ventricle

Question 17

What % of the combined ventricular output is provided by the right ventricle?

Answer 17

66%

Question 18

What is the fetal pO2?

Answer 18

2-4kPa

Question 19

Is the foetus able to metabolise aerobically with a pO2 of 2-4kPa?

Answer 19

Yes

Question 20

What is required for a foetus to metabolise aerobically?

Answer 20

Adequate delivery of oxygen to the tissues

Question 21

What factors ensure adequate delivery of oxygen to peripheral tissues?

Answer 21

• Layout of the circulation system
• High levels of foetal haemoglobin
• High perfusion rates of the organs
• Decreased oxygen requirements

Question 22

How does foetal haemoglobin differ to that of adults?

Answer 22

• Higher percentage of haemoglobin F

- High haemoglobin concentration

Question 23

What % of fetal haemoglobin is HbF?

Answer 23

75%

Question 24

What is the haemoglobin concentration in a foetus?

Answer 24

18g/dl

Question 25

How does HbF differ from adult haemoglobin?

Answer 25

Lower affinity for 2,3-diphosphoglycerate (2,3 DPG)

Question 26

What is the result of HbF having a lower affinity for 2,3 DPG?

Answer 26

It allows for increased binding of oxygen with greater affinity and better oxygen extraction in the placenta

Question 27

What is the importance of the greater affinity and better oxygen extraction of HbF?

Answer 27

It compensates for the relatively lower oxygen tension of the maternal blood supplying the chorion

Question 28

Is is meant by the P50 value?

Answer 28

The partial pressure of oxygen at which the protein is 50% saturated

Question 29

What does a lower P50 value mean?

Answer 29

Greater affinity

Question 30

What is the P50 value for fetal haemoglobin?

Answer 30

2.4kPa

Question 31

What is the P50 value for adult haemoglobin?

Answer 31

3.5kPa

Question 32

How does the oxygen saturation curve of fetal haemoglobin compare to that of adult haemoglobin?

Answer 32

It is left-shifted

Question 33

When should the cord be clamped after birth in uncompromised babies?

Answer 33

1-3 minute from complete delivery, or until cord stops pulsating

Question 34

When should the cord be clamped after birth in babies requiring resuscitation?

Answer 34

Insufficient evidence to recommend a time, but resuscitation is the priority

Question 35

Is there any additional benefit of delaying cord clamping beyond 5 minutes?

Answer 35

No

Question 36

What are the advantages of delayed cord clamping?

Answer 36

- Neonates continue to receive oxygen from placenta | - Haemoglobin increased immediately after delivery

Question 37

How long do neonates continue to receive oxygen from the placenta for?

Answer 37

For as long as the cord os pulsating

Question 38

When is it particularly advantageous for the neonate to continue to receive oxygen from the placenta?

Answer 38

If there was fetal hypoxia during labour

Question 39

Is the haemoglobin increase seen after birth with delayed cord clamping sustained?

Answer 39

No - there is no significant difference in haemoglobin at 2-6 months of age

Question 40

What advantage of delayed cord clamping is seen at 2-6 months?

Answer 40

Increased iron stores

Question 41

What is the disadvantage of delayed cord clamping?

Answer 41

Increased risk of neonatal jaundice

Question 42

What does delayed cord clamping have no impact on?

Answer 42

- Risk of polycythaemia needing treatment - Maternal outcomes in terms of postpartum haemorrhage or maternal mortality - Neonatal mortality - Long-term neurodevelopment outcomes

Question 43

What are the advantages of delayed cord clamping in preterm infants?

Answer 43

- Reduction in blood transfusions - Lower incidence of NEC - Lower incidence of intraventricular haemorrhage

Question 44

What are the disadvantages of delayed cord clamping in preterm infants?

Answer 44

Peak bilirubin concentration is increased

Question 45

What does delayed cord clamping have no effect on in preterm infants?

Answer 45

- Severe intraventricular haemorrhage (grade 3 or 4) - Periventricular leukomalacia - Mortality - Neurodevelopmental outcomes