18) Fetal Physiology Flashcards Preview

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Flashcards in 18) Fetal Physiology Deck (22)
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1
Q

What factors optimise diffusion across the placenta?

A

Small diffusion barrier- decreases as pregnancy proceeds

Concentration gradient between pO2 in mother and fetus

2
Q

What maternal and fetal factors increase gas exchange?

A

Increased maternal 2,3-BPG
Fetal haemoglobin
Double Bohr effect

3
Q

Describe the features of fetal haemoglobin:

A

HbF from 2 alpha and 2 gamma subunits

Increased affinity for O2 as doesn’t bind 2,3-BPG as well as HbA

4
Q

What is the double Bohr effect?

A

As CO2 passes into maternal blood, pH decreases and oxygen is given up
At same time, CO2 given up by fetus, which increases pH and increases fetal affinity for O2

5
Q

What promotes CO2 transfer from fetus to mother?

A

Progesterone driven hyperventilation in mother which lowers pCO2 of maternal blood providing a conc. grad.

6
Q

What are the shunts in fetal circulation?

A
Ductus venosus (bypass liver)
Foramen ovale (RA -> LA)
Ductus arteriosus (bypass lungs)
7
Q

What is the function of the ductus venosus?

A

Connects umbilical vein to IVC

Bypasses liver to maintain saturation

8
Q

What is the function of the crista dividens?

A

Directs oxygenated blood to LA via foramen ovale

9
Q

What is the function of foramen ovale?

A

Shunt from RA to LA so greater supply to LV to supply blood to brain and body

10
Q

What is the function of ductus arteriosus?

A

Between pulmonary artery and aorta to bypass lungs and minimise drop in O2 saturation

11
Q

Describe the fetal response to hypoxia?

A

Redistribution of flow to protect supply to heart and brain
Decrease HR to reduce O2 demand
Increased Hb

12
Q

If hypoxia is chronic, what could be the result for the fetus?

A
Growth restriction 
Behavioural changes (less movement)
13
Q

What hormones are needed for fetal growth?

A

Insulin, IGF II (T1), IGF I (T2-3), leptin

14
Q

What is asymmetrical growth restriction?

A

Abdominal growth lags, head spared

15
Q

What is symmetrical growth restriction?

A

Generalised and proportional restriction

16
Q

What are the functions of amniotic fluid?

A

Protection

Practice breathing movements

17
Q

Describe the changes to amniotic fluid volume during pregnancy:

A

Low to start until fetal kidneys mature and volume rapidly increases

18
Q

Describe the main components of amniotic fluid:

A

Water, electrolytes, creatinine, urea, sloughed off fetal cells

19
Q

What is meconium?

A

Debris from swallowed amniotic fluid

20
Q

When is meconium excreted?

A

After birth

If fetus is in distress (fetal hypoxia)

21
Q

What is amniocentesis?

A

Sampling of amniotic fluid for collection of fetal cells

22
Q

Why is physiological jaundice of fetus common?

A

Fetus can’t conjugate bilirubin and can’t excrete it