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3 Reproduction Unit > 15 Fetal Physiology > Flashcards

15 Fetal Physiology Flashcards

1
Q

The uterine arteries bathe the chorionic villi in maternal blood via the umbilical veins and arteries. Which of these carries oxygenated blood?

A
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2
Q

Outline how the fetus receives enough oxygen despite the increase in maternal blood pH which would shift the oxygen dissociation curve to the left (increase maternal affinity for oxygen).

A

Increase in 2,3-BPG produced

Oxygen dissociation curve shifts right

Promote release to fetus

Fetal blood has lower partial pressure of oxygen

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3
Q

How does fetal haemoglobin differ from normal haemoglobin? When is fetal haemoglobin predominant (ie which week)?

A

Fetal haemoglbin doesn’t bind to 2,3-BPG - so greater affinity for O2

Predominant: from week 12

2 alpha and 2 gamma subunits

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4
Q

Explain what the Bohr effect is and how this speeds up oxygen transfer from the mother to the fetus

A
  • Double bohr effect
    • CO2 passes into intervillous blood- pH decrease- decreased affinity for O2 in mother
    • Fetus giving up CO2- increased pH- increase affinity for oxygen
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5
Q

Explain how CO2 is able to transfer from the fetus to the mother.

A

Proggesterone induced Hyperventilation

Lower conc of CO2 in maternal blood- gradient allows gas exchange

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6
Q

What is the haldane effect?

A
  • Maternal Hb gives up oxygen- accepts increasing amounts of CO2
  • Fetal Hb gives up more CO2 as oxygen accepted
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7
Q

What is fetal distress? Explain how it can occur and give a specific cause of it.

A

Compromise of the fetus due to inadequate oxygen or nutrient supply

Fetal response to hypoxia

Vagal stimulation–> BRADYCARDIA

Specific cause:

Smoking- chronic hypoxaemia- intrauterine growth restriction

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8
Q

Describe the 3 shunts that occur in the cardiovascular system of the fetus:

A
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9
Q

Why is it important that the majority of the blood in fetal circulation bypasses the liver?

A
  • Live is proportionately very large- could potentially consume whole fetal circulation
  • To maintain high level of oxygen arriving to brain and rest of body
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10
Q

What happens to the foramen ovale at birth?

A

In fetus: pressure in right atrium higher than left- blood shunts

At birth: pressure reverses- foramen ovale shunts

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11
Q

Which of the following processes is predominant in each of the trimesters: Hyperplasia or Hypertrophy

A
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12
Q

Differentiate between symmetrical and asymmetrical growth restriction. What can cause growth restriction of the fetus?

A

Cause: maternal malnutrition

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13
Q

What are the functions of amniotic fluid? What is it composed of?

A
  • Lung development substances
  • Mechanical protection

Composition:

  • Electrolytes
  • Creatinine
  • Urea
  • Bile pigments
  • Renin
  • Glucose
  • Hormones
  • Fetal cells
  • Lanugo
  • Vernix caseosa
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14
Q

How does the volume of amniotic fluid relate to the size of the fetus?

A

Size of fetus= directly proportional to volume of amniotic fluid

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15
Q

What is amniocentesis and what can it test for?

A

WHAT?

Apiration of amniotic fluid- contains fetal cells

TESTs?

Fetal karyotyping

Eg Down’s syndrome

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16
Q

Does amniocentesis carry a risk?

A

Yes= invasive and carries risk of miscarriage

17
Q

What is meconium?

A

Earliest stool of infant

Debris from the GI tract- accumulates as meconium

18
Q

Meconium staining is a clinical sign of fetal distress. Outline how this occurs.

A

Premature meconium release from GI tract

Fetus can potentially inhale it (meconium aspiration)

19
Q

How is amniotic fluid produced? When does it start to be produced?

A

Essentially= fetal urine- starts at around 9 weeks

20
Q

How is amniotic fluid recycled?

A
  • Inhaling- fetus inhales fluid- helps lung development esp surfactant
  • Swallowing- enters fetal GI tract
21
Q

What is amniotic fluid composed of?

A

Water, electrolytes, fetal skin (lost in pregnancy)

22
Q

Why do some babies get physiologically jaundice (less than 24hrs) ?

A

Delay in newborns ability to conjugate and excrete bilirubin

In utero clearance of fetal bilirubin= handled by placenta

23
Q

What is the approximate pO2 of fetal blood?

A

4kPa

24
Q

Useful diagram showing shunts:

A
25
Q

List some of the hormones requird for fetal growth:

A
26
Q

Apprximately how much amniotic fluid is there at 8 weeks and at 38 weeks gestation?

A

10ml- 8 weeks

1L- 38 weeks

27
Q

Outline how amniotic fluid is recycled in the fetus:

A

3 Reproduction Unit (21 decks)

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