Pregnancy Physiology Flashcards
What happens to the cardiovascular system during pregnancy?
SV up 30%, HR up 15% & cardiac output up 40%
systolic BP is unaltered
diastolic BP is reduced in the 1st and 2nd trimester, returning to non-pregnant levels by term
enlarged uterus may interfere with venous return which can lead to ankle oedema, supine hypotension and varicose veins
What happens to the pulmonary system during pregnancy?
Pulmonary ventilation up by 40%, tidal volume from 500 - 700ml (due to effect of progesterone on respiratory centre)
Oxygen requirements increase by only 20%, therefore over breathing leads to a fall in pCO2 - this can give rise to a sense of dyspnoea that may be accentuated by elevation of the diaphragm
BMR up 15% - this may be due to increased thyroxine and adrenocortical hormones - women may hence find warm conditions uncomfortable
What are the changes to the blood in pregnancy?
Maternal blood volume up 30%, mostly in 2nd half - red cells up 20% but plasma up 50% Hb falls
Low grade increase in coagulant activity
rise in fibrinogen and Factors VII, VIII, X, also an increase in cholesterol
fibrinolytic activity is decreased - returns to normal after delivery (placental suppression?)
prepares the mother for placental delivery
leads to increased risk of thromboembolism
Platelet count falls
WCC & ESR rise
What are changes in the urinary system in pregnancy?
blood flow increase by 30%
GFR increases by 30-60%
Salt and water reabsorption is increased by elevated sex steroid levels
Urinary protein losses increase
Urea and creatinine levels are decreased
What are the biochemical changes assocaited with pregnancy?
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
What are liver changes in pregnancy?
Unlike renal and uterine blood flow, hepatic blood flow doesn’t change
ALP raised 50%
Albumin levels fall
What are changes of the uterus during pregnancy
100g → 1100g
hyperplasia → hypertrophy later
increase in cervical ectropion & discharge
Braxton-Hicks: non-painful ‘practice contractions’ late in pregnancy (>30 wks)
retroversion may lead to retention (12-16 wks), usually self corrects
