Maternal Adaption of the Circulatory System Flashcards
From the 7th week of pregnancy, how much can the heart rate increase by?
20%
Why does the heart rate increase during pregnancy?
To compensate for a decrease in systemic vascular resistance (caused by progesterone)
Why does cardiac output decrease during pregnancy?
As the heart rate increases, diastolic filling time is reduced so less blood is being pumped out with each beat
What effect does an increase in heart rate have on atrial emptying?
It reduces the efficientcy
What is blood pressure?
Cardiac output x Systemic vascular resistance
From the 7th week of pregnancy, how much can blood pressure decrease by?
10% as a result of peripheral vasodilation
As blood pressure falls, does the cardiac output increase or decrease?
Increases
At how many weeks of pregnancy would you expect blood pressure to be at its lowest?
24 weeks
What is the normal average cardiac output and what is the average cardiac output during pregnancy?
5 litres per minute - normal
7.2 litres per minute during pregnancy
Between which weeks of pregnancy is systemic vascular resistance at its lowest?
14-24 weeks
During labour, what causes blood from the uterus to return to the maternal circulation?
Contractions
How many milliliters of blood can be shifted back to the maternal circulation with each contraction?
Up to 500 milliliters
As blood is returned to the maternal circulatory system, what effect does this have on:
Venous Return
Cardiac Output
Both increase
What is haemodilution?
The increase in plasma volume causing the blood to become diluted
By what percentage does the red blood cell mass increase by?
18-25%
