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Semester 3 - reproduction > 14. Maternal physiology and pregnancy > Flashcards

14. Maternal physiology and pregnancy Flashcards

1
Q

What are the main hormones that drive adaptations during pregnancy?

A
  • hCG
  • Estrogen
  • Progesterone
  • Relaxin
  • hPL
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2
Q

function of hCG?

A

maintain corpus lute for oestrogen and progesterone production

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3
Q

why does the level of hCG decrease in the 2nd trimester?

A

placenta takes over oestrogen and progesterone production so no need to maintain corpus luteum

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4
Q

Is the fetus recognised by the mother immune system?

A
  • Recognised by maternal immune system

- Incited allo-response is not cytotoxic

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5
Q

Why isn’t there a cytotoxic response to the fetus?

A
  • Progesterone and cells of the trophoblastic cells of the placenta produce sHLA-G complex
  • induces release of IL10
  • IL10 induces formation of Th2 cells from naive CD4+ T helper cells driving balance of T helper cells to regulatory Th2 cells rather than cytotoxic Th1 cells
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6
Q

What conditions may be more/less severe during pregnancy?

A
  • Higher attack rate and severity of certain viral pathogens ie. varicella
  • May improve certain autoimmune conditions e.g. psoriasis
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7
Q

What are the respiratory changes?

A
  • Tidal volume increases 30-40%
  • respiratory rate stay fairly the same
  • Increase PaO2, decrease PCO2
  • minute ventilation increased by up to 50%
  • ERV decreases 20%
  • total lung capacity decreases 5%
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8
Q

What is minute ventilation?

A

Respiratory Rate x Tidal Volume

- tidal volume increases in pregnancy

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9
Q

What are the changes to partial pressures in pregnancy?

A

Increase pO2 and decreased pCO2

- pH would increase

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10
Q

Why does the tidal volume increase?

A
  • increase in subcostal angle (from 68 to 103)
  • chest diameter increases 2cm or more
  • down regulation of residual volume
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11
Q

How does progesterone affect respiratory drive?

A

Progesterone acts on the respiratory centre, causing sensitisation of the chemoreceptors to CO2 changes leading to increased respiratory effort and reduction in pCO2

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12
Q

When and what causes decreases in total lung capacity?

A

Later in pregnancy, elevation of diaphragm by about 4cm

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13
Q

What is the normal ABG in pregnancy?

A

Pregnant women expected to have

(partially) compensated respiratory alkalosis
- high pO2, low pCO2, reduced HCO3-

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14
Q

What is a physiological consequence of changes in the respiratory system and what is most likely due to?

A

Dysponea of pregnancy

  • 60-70% of patients
  • Most likely due to progesterone induced hyperventilation and decreased PaCO2
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15
Q

What can distinguish physiological dysponea from pathological dysponea in pregnancy?

A
  • Must be progressive not acute
  • should not be present with any other symptoms (e.g. cough, pain)
  • chest auscultation should be clear
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16
Q

What are some pathological causes or exacerbating factors of physiological dysponea?

A 
Consider underlying disease (e.g. asthma)
• Cardiac
• Anemia
• DVT/PE **
• Asthma
• Pneumonia/ARDS
• Pulmonary edema
17
Q

how are the respiratory needs of the mum and foetus met?

A

increased ventilation

18
Q

what are the cardiovascular needs of the mum?

A
  • Fill utero-placental-fetal circulation
  • Oxygenate growing uterus - very vascular! High demand
  • Protect from impaired venous return
  • Prepare for potential blood loss during delivery
19
Q

how are the cardiovascular needs of mum and foetus met?

A

Volume expansion

Clotting mechanisms

20
Q

What are the cardiovascular changes?

A
  • increase in CO
  • increase in plasma volume - from 4.5 to 6 L/min
  • decrease in total peripheral resistance
  • decrease blood pressure (in first 2 trimesters)
21
Q

What causes increase in cardiac output?

A
  • Early in pregnancy is due to increase in stroke volume

- late is due to increase in heart rate (up to 95 bpm)

22
Q

What is the normal blood pressure in pregnanacy?

A

<140/90

23
Q

What causes fall in total peripheral resistance?

A

Progesterone causes relaxation of vascular smooth muscle

  • causes lower blood pressure in the first and second trimester, but this usually returns to normal by the third trimester.
24
Q

what can occur in pregnancy due to increased plasma volume/?

A

Due to the increase plasma vilume, flow murmurs can occur in pregnancy, as well as upward displacement of the apex beat.

25
Q

What happens to clotting ability in pregnancy and how does this occur?

A

Increase coaguability:

  • Increased Procoagulants (ex. Fibrinogen, Factor VIII, vWF)
  • Decreased anticoagulants (ex. Protein S)
  • Reduced fibrinolysis
26
Q

Why is hypercoaguability necessary in pregnancy?

A

Prevent haemorrhage

27
Q

How is stroke volume increased?

A
  • Drop in blood pressure (due to progesterone) stimulates RAAS
  • progesterone and oestrogen also directly induce renin release from kidneys
  • oestrogen causes angiotensinogen release from liver
  • aldosterone released due to angiotensin II causes salt and water retention increasing plasma volume
28
Q

What effect of angiotensin II is not present during pregnancy?

A

It does not cause vasoconstriction

- progesterone down regulates vasoconstriction

29
Q

What are the consequences of changes in the cardiovascular system? (3)

A

Increased RAAS
- Peripheral oedema

Change in plasma volume&raquo_space; change in RBC volume
- Dilutional anemia

Clotting: HYPERCOAGULABLE STATE
- Increased number of thromboembolic events

30
Q

What can exacerbates the oedema?

A

Compression of the vena cava by the gravid uterus causing venous stasis

31
Q

Why does dilutional anaemia occur, when is it treated and what other causes should be considered?

A

Rise in plasma volume more than rise in RBC number

  • only treated if < 100 Hb
  • consider other causes (iron and folate deficiency )
32
Q

What can venous distention and engorgement cause/

A

Varicose veins and haemorrhoids

33
Q

What test should be done if venous thromboembolism is suspected in pregnancy?

A

Ultrasound doppler

- D-dimers should not be done, will be high in pregnancy regardless (false positive result)

34
Q

why can warfarin not be given to treat thromboembolic diseases in pregnancy?

A

warfarin is teratogenic and can cross the placenta.

35
Q

how are the renal needs of mum and foetus met?

A

increased GFR

36
Q

what are the renal changes?

A

Systemic vasodilation = Increased RBF

  • Increase GFR by 50%
  • progesterone induced smooth muscle relaxation of ureters

Semester 3 - reproduction (19 decks)

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