Lecture 17- Maternal physiology and pregnancy Flashcards
Why does the body need to adapt
x
To allow the foetus to grow
-
Volume support
- Volume expansion
- Vasodilation
-
Nutrition
- Increased respiration
- Insulin resistance
- Increased absorption
-
Waste clearance
- Increased GFR
- Hepatocellular stimulation
-
Pregnancy maintenance
- Uterine quiescence
- Immunologic sequestration
-
Childbirth
- MSK
- Clotting
what drives maternal adaptations
hormones etc
- hCG
- oestrogen
- progesterone
- relaxin
- softens ligaments and widens the cervix
changes in immunity
the foetus is genetically different (hemi-allograft)
- will be recognised by the maternal immune system if the mother does not become immunosuppressed
–> allo-response is not cytotoxic
Pregnancy= immunosuppressed state therefore
- Higher attack rate and severity of certain viral pathogens i.e. varicella, flu etc
- May improve certain autoimmune conditions
immune changes
Reduced Th1 (cytotoxic) and increased Th2 (more regulatory)
changes in respiration
- increased inute ventilation (Increased tidal voluem and respiratory rate
- decrease paCO2
- increased paO2
- pH changes
- decreased functional residual capacity
anatomical changes in respiratory system
growth of the foetus during pregnancy causes upward displacement of the diaphragm.
However, this does not decrease the total lung capacity significantly as there is also an increase in the transverse and anterior-posterior diameters of the thorax.
In pregnancy a woman faces an increase in their metabolic rate, which leads to an increased demand for oxygen. how does the body adapt to help the mother meet the oxygen demand?
The tidal volume and the minute ventilation rate increases
Many women experience hyperventilation during pregnancy, it is thought that the reason for this is the increased carbon dioxide production and the increased respiratory drive caused by
progesterone.
This hyperventilation results in a respiratory alkalosis with a compensated increase in renal bicarbonate excretion.
need to still consider pathological causes and excerbating factors of dyspnea
- cardiac
- anaemia
- DVT/PE
- Asthma
- Pneumonia/ARDS (acute resp distress syndrome)
- PE
changes in cardiovascualr system
- Increased SV (early pregnancy)
- Increased HR (late pregnancy)
- Increased cardiac output (CO= SV x HR)
blood pressure and pregnancy
As discussed above, during pregnancy progesterone levels increases. Progesterone acts to decrease systemic vascular resistance in pregnancy which leads to a decrease in diastolic blood pressure during the first and second trimester of pregnancy.
In response to this the cardiac output increases by about 30-50%. An increase in blood pressure in pregnancy could be an indication of pre-eclapmsia.
why does the total blood volume increase during pregnancy
Pregnancy (progesterone and ostrogen) results in the activation of the renin-angiotensin-aldosterone system, leading to an increase in sodium levels and water retention. This means that the total blood volume increases= Increased stroke volume
- release of renin from kidneys
- angiotensiongen from the liver
consequences within the cardiovascular system
- icnreased RAAS- peripheraledema
- chganges in plasma volume >>>> change in RBC volume –> dilutional anaemia
- clotting - hypercoagylabvle state = increased number of thromboembolic events
clotting during pregnancy
- Increased procoagulants (eg. Fibrinogen, factor VIII, vWF)
- Decreased anticoagulants e.g. protein S
- Reduced fibrinolysis
changes in the renal system
Increased cardiac output and systemic vasodilation during pregnancy causes an increase in renal plasma flow
- Which increases the GFR by about 50-60%.
- This would mean that there is an increase in renal excretion, so in pregnancy the plasma levels of urea and creatinine will be lower.
- decreased PCT absorption
decreased PCT absorption=
glucosuria–> not enough time for reabsorption