Physiological adaptations in pregnancy

Question 1

Describe blood volume increase during pregnancy

Answer 1

First trimester- blood volume increases
Second trimester- blood volume expands rapidly

Third trimester- Total blood volume rises slower

Plasma volume can increase up to 45%

Question 2

Describe plasma and erythrocyte changes during pregnancy

Answer 2

Initial rise in plasma volume Followed by increase in total erythrocyte volume.

Erythropoises is stimulated by the kidneys producing more erythropoietin.

Red cell mass increase up to 20%

Increase in RBC is less than for plasma

Question 3

Describe Dilutional Anaemia

Answer 3

Hb concentration falls from 150g/l before pregnancy to 120g/l during third trimester

Question 4

What causes the increase in plasma volume during early pregnancy?

Answer 4

1. Vasodilation
2. Decreased peripheral vascular resistance
3. Activation of renin-angiotensin-aldosterone (RAAS) system
4. Retention of sodium and an increase in total body water

Question 5

Describe cardiac output changes during pregnancy

Answer 5

First trimester- cardiac output increase by 35-40%
Second/third trimester- Slight increases
50% increase at term

Increased distribution of cardiac out put to uterus during pregnancy 17%

Question 6

What causes increased cardiac output during pregnancy?

Answer 6

increased heart rate (of about 25%) and increased stroke volume (of about 25%)

Question 7

When is the blood pressure at its lowest?

Answer 7

17-24 weeks