Maternal Physiology (Pregnancy) Flashcards Preview

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Flashcards in Maternal Physiology (Pregnancy) Deck (54)
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1

What is the purpose of maternal cardiovascular changes occurring with pregnancy?

Improve foetal oxygenation and nutrition

2

What are the CV anatomic changes of pregnancy?

-heart displaced upward and to left
-heart assumes more horizontal position (apex moved laterally)
-ventricular muscles mass increase (due to inc in circulating blood volume)
Occur due to diaphragmatic elevation by enlarging uterus

3

What is the primary functional change of CV system with pregnancy?

Increase in CO

4

How much does CO increase with pregnancy?

30-50%.
50% of increase in first 8 weeks

5

what is the mechanism of increased CO during pregnancy?

-First half: due to inc SV
-Second half: inc HR (SV returns normal)

6

What causes the alterations in stroke volume?

Alterations in circulating blood volume and systemic vascular resistance

7

When is the peak increase in blood volume during pregnancy?

Peak of 45% increase at 32 weeks

8

Why does systemic vascular resistance decrease?

-1. Progesterone relaxing SM
-2. Inc production of vasodilators (PGs, NO, ANP)
-3. Arteriovenous shunting to uteroplacental circulation

9

What may cause a decrease in CO during pregnancy?

Venous return to heart being impeded by venal caval obstruction by enlarging gravid uterus

10

What is the path of venous return from lower extremities in the setting of complete vena caval obstruction in term pregnancy?

Dilated paravertebral collateral circulation

11

How does maternal HR change in pregnancy?

Increases as pregnancy progress.
Increases 10-18bpm over non pregnant value by term

12

What happens to dBP with pregnancy?

Decreases begin in 7th week; maximal decrease of 10mmHg by 24-32 weeks

13

What is inferior vena cava syndrome?

10% women have symptoms of:
-dizziness
-light headedness
-syncope
when lying supine. May be due to insufficient shunting by paravertebral circulation when gravid uterus occludes IVC

14

What are the normal CV PEx findings during pregnancy?

-Increased S2 split with inspiration
-Distended neck veins
-Low grade systolic ejection murmur (? due to increased flow across aortic and pul valves)
-Many have S3 gallop

15

What is the primary mediator of the respiratory changes occurring with pregnancy?

Progesterone

16

How does oxygen consumption change with pregnancy?

20% increase (50mL/min)

17

How is the increased oxygen consumption utilised within the pregnant body?

Ff the increase:
-50% used by uterus and contents
-30% heart and kidneys
-18% respiratory muscles
-remainder to mammary tissues

18

What is the primary respiratory parameter changed with pregnancy?

30-40% increase in minute ventilation

19

What are the results of the increased minute ventilation?

Changes in acid-base
-progesterone sensitises central chemoreceptors to CO2 -> increased respiration and decreased arterial PCO2
-respiratory alkalosis compensated by renal excretion of bicarbonate

20

What causes the dyspnoea of pregnancy?

Physiologic response to low arterial PCO2

21

URT changes pregnancy

-allergy like symptoms or chronic colds
-mucosal hyperemia producing nasal stuffiness and increased nasal secretions

22

What do ABGs in pregnancy usually show?

Compensated respiratory alkalosis

23

What are the haematologic changes of pregnancy?

-increase in plasma volume
-increase in red cell volume
-increase in coagulation factors

24

When does maternal plasma volume peak?

30-34 weeks then stabilises

25

What is the mean plasma volume increase?

-50% singleton
-Greater if multiple

26

What is the maternal blood volume increase with pregnancy?

35% by term

27

What is the total additional iron requirement during pregnancy?

Additional 1000mg
-500mg to increase red cell mass
-300mg to foetus
-200mg to compensate for iron loss

28

What is the recommended daily iron need in a pregnant woman who is not anemic?

60mg

29

How do WBCs change during pregnancy?

-Mild increase throughout
-More pronounced increase in labour: primarily increased granulocytes linked with stress induced demargination (cf disease associated inflammatory response)

30

How do clotting factor concentrations change with pregnancy?

-FI (fibrinogen) 50% increase
-VII, VIII, IX, X 50% increase
-Promthrombin (II), V, VII unchanged
Inhibitors of coagulation (protein C and S) both decrease