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
What causes the increase CO in pregnancy?
Sodium retention and volume expansion
What are stimuli causing increased sodium retention and volume expansion causing the increase in CO in pregnancy?
1) Increased RAAS - oestrogen
2) Increased aldosterone - progesterone and vasodilatory prostaglandins
3) Increased renin - stimulation of sympathetic activity by ‘shunting’ of blood to uterine circulation, renal sodium loss due to increased GFR, hCG
Where does regional blood flow increase in pregnancy?
Everywhere bc of vasodilation and increase in CO incl. breasts, gut, skin, kidney, uterus etc
What happens to skin blood flow in pregnancy and what are the effects of this?
1) Predominantly increases unhands and feet
2) This leads to an increased skin temperature, nail growth and % of hairs actively growing pc of increased peripheral temperature
3) It also causes the disappearance of Raynaud’s
4) Causes the presence of nose bleeds, nasal stuffiness and snoring
What are the changes to the respiratory system in pregnancy?
1) Increased tidal volume (and minute volume)
2) Decreased PaCO2
3) Increased PaO2
4) Decreased functional reserve capacity (FRC)
5) Decreased total lung capacity (TLC)
6) Decreased expiratory reserve volume (ERV)
7) Decreased residual volume
8) Deep breathing occurs
Why does FRC, TLC and ERV decrease in pregnancy?
Due to compression of the diaphragm by the uterus
What lung volume measures do not change in pregnancy?
1) RR
2) Vital capacity (VC)
3) FEV1
What is an abnormal RR in pregnancy?
> 20 (RR does not increase)
Even though RR does not increase in pregnancy, what may pregnant woman experience due to the other changes in lung volumes?
Sense of breathlessness
What are the ABG changes in pregnancy?
1) pH 7.40-7.47 (increase/unchanged?)
2) Decreased pCO2 (3.6-4.3)
3) Increase pO2 (12.6-14.0)
4) Decrease in bicarbonate (18-22) - to balance out the decrease in CO2 so that pH stays constant
5) No change to base excess
What happens to maternal oxygen consumption in pregnancy?
It increases
What happens to the diaphragm in pregnancy?
It relaxes, so the rib cage and costal margin is higher
What hormone stimulates deep breathing in pregnancy?
Progesterone
How does blood coagulability change in pregnancy and why?
- It increases - pregnancy is a hyper-coagulability state
- Changes occur to induce a low grade increase in coagulability
- This is advantageous at delivery
- No change in bleeding time
How does coagulation increase in pregnancy?
1) Factors VII, VIII and X increase
2) Plasma fibrinogen increases therefore ESR increases
3) Fibrinolytic activity decreases e.g. decrease in antithrombin III
What happens to ESR in pregnancy?
It increases
When is the hyper-coagulability a problem and what can be done about it?
- Not good if have an underlying clotting problem bc it can lead to excessive clotting problems
- Put them on LMW heparin
What are the anatomical renal changes in pregnancy?
1) Kidney size increases by 1cm - goitre
2) Kidney volume increases by 30%
3) Dilation of the renal, calyces, pelvis and ureters
What are the physiological renal changes in pregnancy?
1) GFR increases by 40-65% (100%) - need increased capacity for excretion of creatinine
2) Plasma concentration of renal function i.e. creatinine and urea decrease
3) Effective renal plasma/blood flow increases
4) Glycosuria - bc high renal blood flow and slighter higher glucose
5) Calciuria - lose a bit of calcium
6) Urinary frequency increases - weight of embryo on bladder
7) Urinary stasis
8) Increased urinary protein and glucose
What type of infections are pregnant women more at risk of and why is this a problem?
- Kidney infections - can lead to preterm labour, irritates the uterus
- UTIs
Why does urinary stasis occur in pregnancy and why is this a problem?
- Urinary stasis occurs due to dilation of collecting system
- Smooth muscle of pelvic floor dilates, causing pooling of urine
- This makes UTIs v common in pregnancy
- Worry about using antibiotics bc of microbiome
What is the difference between control of osmolarity in normal women vs pregnant women?
1) Normally fall in osmolarity leads to switching off of ADH and peeing lots of dilute urine
2) In pregnant women the ADH response to low osmolarity is reset do the new state of decreased osmolality is considered normal ( - the osmotic threshold for ADH decreases)
- So ADH is not switched off when plasma osmolality is low so water is not lost as it is needed
What are GI tract changes in pregnancy?
1) Gastric pH increases
2) Intestinal motility is reduced
3) This leads to constipation and may lead to delayed absorption
4) Reduced smooth muscle tone (smooth muscle is relaxed)
5) Decreased liver enzymes (AST, ALT, GGT)
5) Increased ALP
What is the effect of reduced smooth muscle tone in pregnancy?
1) Decreased cardiac sphincter tone
2) Decreased motility and mobility
3) Lower oesophageal sphincter tone
4) This leads to biliary stasis, increased gastric reflux (heartburn) and increased nutrient/water reabsorption and increased risk of aspiration
What happens to serum albumin concentration in pregnancy?
It increases
What happens to venous hydrostatic pressure in pregnancy?
It increases
What happens to plasma protein concentration and therefore plasma oncotic pressure in pregnancy?
Decrease incl. platelets
Function of which WBCs is reduced in pregnancy?
Lymphocytes (T cells)
What neurological changes occur in pregnancy?
1) Increased CSF pressure
2) Engorgement of epidural veins
3) Decreased MAC
4) Decreased LA (left atrial?) volumes required
What musculoskeletal changes occur in pregnancy?
1) Increased ligamentous laxity
2) Increased risk of dislocation
3) Increased lumbar lordosis
