PREGNANCY: physiological changes Flashcards
How does the cardiovascular system change during pregnancy?
During pregnancy, stroke volume (SV) increases by 30%, heart rate (HR) increases by 15%, and cardiac output increases by 40%.
How does systolic and diastolic blood pressure change during pregnancy?
Systolic blood pressure remains unaltered, while diastolic blood pressure is reduced in the 1st and 2nd trimester, returning to non-pregnant levels by term.
What are the effects of an enlarged uterus on venous return?
An enlarged uterus may interfere with venous return, leading to ankle oedema, supine hypotension, and varicose veins.
How does the respiratory system change during pregnancy?
Pulmonary ventilation increases by 40%, and tidal volume increases from 500ml to 700ml due to the effect of progesterone on the respiratory centre.
Why do pregnant women experience a sense of dyspnoea?
Overbreathing leads to a fall in pCO2, which can give rise to a sense of dyspnoea that may be accentuated by the elevation of the diaphragm.
How does basal metabolic rate (BMR) change during pregnancy?
Basal metabolic rate (BMR) increases by 15%, possibly due to increased thyroxine and adrenocortical hormones, causing women to find warm conditions uncomfortable.
How does maternal blood volume change during pregnancy?
Maternal blood volume increases by 30%, mostly in the second half of pregnancy.
How does haemoglobin (Hb) concentration change during pregnancy?
Red cell mass increases by 20%, but plasma volume increases by 50%, leading to a fall in haemoglobin (Hb) concentration.
What changes occur in the coagulation system during pregnancy?
There is a low-grade increase in coagulant activity, with rises in fibrinogen and Factors VII, VIII, and X, and decreased fibrinolytic activity, preparing the mother for placental delivery but increasing the risk of thromboembolism.
How does the urinary system change during pregnancy?
Blood flow to the kidneys increases by 30%, and glomerular filtration rate (GFR) increases by 30-60%.
How does glomerular filtration rate (GFR) change during pregnancy?
Glomerular filtration rate (GFR) increases by 30-60% during pregnancy.
What are the biochemical changes related to calcium during pregnancy?
Calcium requirements increase, especially during the 3rd trimester and continuing into lactation. Gut absorption of calcium increases due to increased 1,25 dihydroxy vitamin D.
How does liver function change during pregnancy?
Unlike renal and uterine blood flow, hepatic blood flow does not change. Alkaline phosphatase (ALP) levels increase by 50%, and albumin levels fall.
How does the uterus change in size during pregnancy?
The uterus increases in size from 100g to 1100g, undergoing hyperplasia and later hypertrophy.
What is Braxton-Hicks contraction?
Braxton-Hicks contractions are non-painful ‘practice contractions’ that occur late in pregnancy (after 30 weeks).
