Physiological Changes in Pregnancy Flashcards
How does plasma volume change in pregnancy and why?
- It increases
- Increases more with multiple pregnancies
- To fill new circulation to uterus
How much does CO increase by in pregnancy?
1.5L
How does RBC mass increase in pregnancy?
- Need oxygen carrying capacity for increased circulation
- Kidney produces lots of erythropoietin in pregnancy which stimulates red cell mass to increase
- Increase more in multiple pregnancies
Why is anaemia not good for pregnancy?
- Have much less tolerance to losing blood at delivery
- More susceptible to infection
What kind of anaemia occurs during pregnancy?
Dilution anaemia
Explain dilution anaemia/haematocrit dilution in pregnancy
- Synthesis of maternal RBCs increases stimulated by epo
- Number of RBCs increases but there is apparent anaemia due to dilution
- Haematocrit falls from approx 40% to 32% bc plasma volume increases more than RBC mass
- Normal, still more oxygen carrying capacity
What happens to 2,3-DPG in pregnancy and why?
- ~30% increase in intracellular 2,3-DPG facilitates offload of oxygen release to fetus
- Rightward shift in oxygen-Hb dissociation curve
What happens to biochemical parameters in maternal blood in pregnancy?
1) Fat soluble products increase - bc triglycerides increase to take fatty acids to the fetus, anything lipid or lipid-soluble also rises
2) Concentration of water soluble products wall - bc of increased water reabsorption to increase plasma volume
Does MCV change in pregnancy?
Normally not - only if iron-deficient anaemia e.g. thalassaemia
Over the whole pregnancy what are the cardiovascular changes in pregnancy and intrapartum?
1) Increase in CO, SV and HR
2) Decrease in TPR (SVR - systemic vascular resistance, same as TPR) and BP
3) Left ventricular hypertrophy
4) Regurgitant murmurs (systolic)
Why does BP not increase if CO and HR increase?
Bc of the decrease in TPR
What happens to TPR in the 1st, 2nd and 3rd trimester?
1) Decrease
2) Decrease
3) Begins to relatively increase by term, still lower than normal
What happens to BP in the 1st, 2nd and 3rd trimester?
1) Decrease
2) Decrease
3) Increase to pre-pregnancy
What happens to CO and HR in the 1st, 2nd and 3rd trimester?
1) Increase
2) Increase
3) Plateaus
What happens to TPR, BP, CO and SV early post delivery?
All increase
Is high BP normal in pregnancy?
No (if anything low is more normal)
What causes TPR to fall in pregnancy?
1) Increase NO synthesis
2) Increase prostacyclin synthesis
3) Increase compliance (more elastic blood vessels) due to structural changes
4) Relaxin?
Describe how NO increases in normal pregnancy and what happens in pre-eclampsia
- NO synthase responds to ACh, histamine and blood flow along the endothelium
- Increased synthesis stimulated by oestrogen
- Gene has oestrogen receptor on promoter
- In pre-eclampsia the endothelium is damaged causing an increase BP
What can cause problems with increased compliance of blood vessels in pregnancy?
- If have a genetic problem with blood vessel walls e.g. Marfan syndrome where you have weak blood vessel walls, it will become apparent
- Prone to aortic swelling and aneurysm