Lecture 14 - Maternal Adaptations Flashcards
Maternal adaptations
Volume support
- volume expansion
- vasodilation
Nutrition
- increased respiration
- insulin resistance
- increased absorption
Waste clearance
- increased GFR
- hepatocelullar stimulation
Childbirth
- increased coagulation
-
Hormones that control changes
Beta HCG - oestrogen and progesterone release
Oestrogen - increases release of prolactin
Progesterone - increases appetite and fat deposition
Relaxin
HPL- insulin resistance
What does a baby need to survive in vivo
Glucose
Oxygen
Amino acids
Immunoglobulin
Clearance of:
CO2
Urea
Immunological changes of the mother
Foetus is recognised by the maternal immune system
Incited allo-response is not cytotoxic
Mother in immunosuppressed state
Respiratory changes
Increased O2 supply needed to meet metabolic demand
Increased CO2 clearance
Therefore: more frequent and deeper breaths
Increased minute ventilation
Increase tidal volume
Respiration rate stays the same
effects:
pH more alkali
ERV - (3rd trimester) decreases as the uterus compresses the lungs
TLC - decreases as diaphragm is elevated
What causes the respiratory changes
Progesterone
Dyspnea in pregnancy
Shortness of breath in pregnancy due to hyperventilation
May have other causes: Cardiac Anaemia DVT and PE Asthma Pulmonary oedema Pneumonia
Cardiovascular changes
Increased HR
Increased stroke volume
Therefore increased cardiac output
Decreased TPR - maintain BP
Increased procoagulants
Decreased anticoagulants except protein S
Reduced fibrinolysis
What causes a decrease in TPR?
Progesterone causes arteriole vasodilation
Normal BP in pregnancy
140/90
Due to increased cardiac output
Procoagulants
Fibrinogen
Factor VIII
vWF
Effects of increasing procoagulants
Can lead to thromboembolic diseases such as DVT and PE
Can’t give warfarin as teratogenic
Pre - eclampsia
Due to placental insufficiency - hypoperfusion and ischaemia
- hypertension
- proteinuria
Symptoms: Headache Visual disturbances RUQ pain - liver microclotting Oedema
Can lead to:
- eclampsia - seizure
- intrauterine growth restrictions
- foetal respiratory distress syndrome
- preterm labour
Treatment: Maintain BP Diuretics and fluid restriction Antihypotensives - Ang II receptor blocker MgSO4 - neuroprotection
How is stroke volume increased
Progesterone and oestrogen stimulates renin release from the kidney which ultimately increases angiotensin II
Angiotensin II acts on the adrenal glands to produce aldosterone which causes increase absorption of NA+ and water in the DCT
Increased plasma volume
Therefore:
Increased venous return
Increased preload - EDV
and increased contractility
Increased stroke volume
Consequences of increased blood volume (RAAS)
Peripheral oedema
Dilutional anaemia - plasma volume increases more than RBC volume
Mild cardiac hypertrophy
Rotation of cardiac axis and displaced apex beat
Split S1 sound - early closure of mitral valve
Loud S3 sound - passing filling of LV
IVC compression
Growing uterus may compress the IVC - reducing venous return and preload
Post delivery:
IVC no longer compressed
Preload increases
CO increases as SV increases
CO decreases to Perla our values 1 hour after delivery
Why are women with aortic stenosis at risk of cardiac arrest during pregnancy?
Aortic stenosis increases afterload
During pregnancy:
IVC compressed decreasing preload
Contractility decreases
Too much stress on the heart
Dilution anaemia
Increased plasma volume due to clotting factors and increased water retention
Less RBC increase - dilutional anaemia
More Hb produced - using up iron and folate
Give women iron tablets
Renal changes
Increased GFR
Increases EPO production
Increases renin production
Increases calcitriol production - increase Ca2+ absorption in gut
Reduced mobility of ureters - progesterone
How is GFR increased
Systemic vasodilation
Increases renal blood flow
Effects of increased GFR
Creating and urea clearance increases
Reduced plasma osmolarity - more filtered
Glycosuria - decreased PCT reabsorption as tubules have less time to act
Increased urine output - urinary frequency (Also compression of bladder by uterus)
Hydronephrosis and hydroureter
Vasodilation and obstruction
Decreased ureteric mobility
Increased size of renal pelvis and calyces - hydronephrosis
Increased size of ureters - hydroureter
Reduced mobility of ureters
Urine stasis
Increased risk of UTIs
