Pregnancy

Question 1

What vascular changes occur in pregnancy?

Answer 1

1) Decreased SVR by 25-30%
2) Increased Cardiac Output by 40%
3) Increased Stroke Volume
4) Increased Heart Rate by 10-20 bpm

Question 2

What happens to the SVR in pregnancy?

Answer 2

Peripheral vasodilatation due to endothelial derived factors e.g. nitric oxide, upregulated by oestradiol.

Begins in first semester

Question 3

What happens to the CO in pregnancy?

Answer 3

Fall in SVR causes compensatory increased CO.
By 8 weeks - increased by 20%
Max CO reached by 20-28 weeks

Question 4

What happens to the Stroke Volume in pregnancy?

Answer 4

Increased CO mostly due to increased SV
This is achieved by:
1) increase in ventricular wall muscle mass and end diastolic volume
2) heart becoming physiologically dilated, increased myocardial contractility

Question 5

What happens to the heart rate in pregnancy?

Answer 5

Increased by 10-20 bpm
Second mechanism of increasing CO
Maintained to term

Question 6

What happens to the blood pressure and blood volume in pregnancy?

Answer 6

1) Decreased BP

2) Increased blood volume

Question 7

When is the most marked change in BP noticeable in pregnancy?

Answer 7

In the 2nd trimester. Nadir at 22-24 weeks.
Already begins in first trimester
Rises to pre-pregnancy levels at term

Question 8

What happens to the plasma volume in pregnancy?

Answer 8

Increases by 50%
Begins in first trimester
Plateaus at 34 weeks
RBC mass only increases by 20-30%
"Physiological anaemia"

Question 9

What changes occur in the pulmonary circulation in pregnancy?

Answer 9

1) Decreased pulmonary vascular resistance by 25-30%
2) No change in CVP
3) No change in pulmonary capillary wedge pressure