Pregnancy: physiological changes Flashcards
Cardiovascular system
SV up 30%, HR up 15% & cardiac output up 40%
BP
systolic BP is unaltered
diastolic BP is reduced in the 1st and 2nd trimester, returning to non-pregnant levels by term
interfere with venous return is due to what
enlarged uterus
interfere with venous return results in
Ankle oedema, supine hypotension and varicose veins
Respiratory system
Pulmonary ventilation up by 40%, tidal volume from 500 - 700ml (due to effect of progesterone on respiratory centre)
Oxygen requirements increase by
only 20%
over breathing leads to
fall in pCO2 - this can give rise to a sense of dyspnoea that may be accentuated by elevation of the diaphragm
BMR increases by?
Why?
15% - this may be due to increased thyroxine and adrenocortical hormones -
women may find warm/cold conditions uncomfortable
warm
due to raised bmr
Maternal blood volume
up 30%, mostly in 2nd half - red cells up 20% but plasma up 50% Hb falls
coagulant activity
Low grade increase in coagulant activity
rise in fibrinogen and Factors VII, VIII, X
fibrinolytic activity is decreased - returns to normal after delivery (placental suppression?
Platelet count falls
WCC & ESR rise/fall
rise
Salt and water reabsorption is increased by what?
elevated sex steroid levels
Urinary system
blood flow increase by 30%
GFR increases by 30-60%
Salt and water reabsorption
Urinary protein losses increase
Calcium
Calcium requirements increase during pregnancy
especially during 3rd trimester + continues into lactation
calcium is transported actively across the placenta
serum levels of calcium and phosphate actually fall (with fall in protein)
ionised levels of calcium remain stable
Gut absorption of calcium increases substantially - due to increased 1,25 dihydroxy vitamin D
