What is the purpose of maternal cardiovascular changes occurring with pregnancy?
Improve foetal oxygenation and nutrition
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
What is the primary functional change of CV system with pregnancy?
Increase in CO
How much does CO increase with pregnancy?
30-50%.
50% of increase in first 8 weeks
what is the mechanism of increased CO during pregnancy?
- Second half: inc HR (SV returns normal)
What causes the alterations in stroke volume?
Alterations in circulating blood volume and systemic vascular resistance
When is the peak increase in blood volume during pregnancy?
Peak of 45% increase at 32 weeks
Why does systemic vascular resistance decrease?
What may cause a decrease in CO during pregnancy?
Venous return to heart being impeded by venal caval obstruction by enlarging gravid uterus
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
How does maternal HR change in pregnancy?
Increases as pregnancy progress.
Increases 10-18bpm over non pregnant value by term
What happens to dBP with pregnancy?
Decreases begin in 7th week; maximal decrease of 10mmHg by 24-32 weeks
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
What are the normal CV PEx findings during pregnancy?
What is the primary mediator of the respiratory changes occurring with pregnancy?
Progesterone
How does oxygen consumption change with pregnancy?
20% increase (50mL/min)
How is the increased oxygen consumption utilised within the pregnant body?
Ff the increase:
What is the primary respiratory parameter changed with pregnancy?
30-40% increase in minute ventilation
What are the results of the increased minute ventilation?
Changes in acid-base
What causes the dyspnoea of pregnancy?
Physiologic response to low arterial PCO2
URT changes pregnancy
- mucosal hyperemia producing nasal stuffiness and increased nasal secretions
What do ABGs in pregnancy usually show?
Compensated respiratory alkalosis
What are the haematologic changes of pregnancy?
When does maternal plasma volume peak?
30-34 weeks then stabilises