Physiological Changes in Pregnancy Flashcards
What are the two main causes of physiological changes during pregnancy?
Intentional: hormones, Adaptive: baby growing inside
What are the three major cardiovascular changes during pregnancy?
- Work increased
- Plasma volume increased
- Peripheral resistance decreased
By what percentage does cardiac output (CO) increase during pregnancy and what factors cause this?
30-50%. This increase is due to rises in heart rate (HR) and stroke volume (SV).
How much does heart rate (HR) increase by the end of the first trimester?
15-25%, The HR increase is typically around 15 bpm.
What is the percentage increase in stroke volume (SV) during the first and second trimesters?
- T1: about 20%
- T2: about 25%
What organ drives plasma volume changes during pregnancy?
Kidneys: water and sodium retention
What adaptations prevent blood pressure from increasing during pregnancy despite volume expansion?
- Vasodilation of existing vasculature
- Adding new vascular beds (e.g., placenta)
What are the effects of decreased peripheral resistance during pregnancy?
- More blood redirected to fetus
- Increased GFR (glomerular filtration rate)
- More blood to kidneys, skin, and nose
- Increased extracellular fluid (oedema)
What mechanical changes occur to lung function during pregnancy?
- Diaphragm pushed up
- Reduced expiratory reserve volume
- Compensatory increase in other lung dimensions
What causes breathlessness in pregnant individuals?
Progesterone tells hypothalamus to breathe deeper as changes in biochemical needs change including increased PO2 and reducing PCO2
What is the effect of increased cardiac output on gas exchange in the lungs during pregnancy?
More blood flows through the lungs more frequently so more O2 and CO2 exchanged
What is the typical blood pH range during pregnancy and what causes this?
7.4-7.47, This is slightly alkaline compared to the normal range of 7.35-7.45, caused by mild hyperventilation state
What renal changes occur during pregnancy related to GFR?
50% increase in GFR
What hormone produced by the kidneys cleaves angiotensinogen into angiotensin II?
Renin
What happens to sodium and potassium transport during pregnancy?
Increased tubule Na+/K+ pump activity and ENaC transporter
What are the consequences of hormonal relaxation of smooth muscle in the urinary tract during pregnancy?
- Increased volume capacity of bladder
- Urinary stasis
- Increased UTI risk
- polyuria and nocturia
What condition is indicated by abnormal urinary protein during pregnancy?
Pre-eclampsia
What happens to blood glucose levels during pregnancy as a result of increased GFR?
Lower blood glucose levels due to increased clearance of glucose
What factors drive SV increase?
These increases in SV are driven by cardiac hypertrophy and endocrine regulation.
What anatomical consequence occurs due to the increase in fluid entering the kidney?
hydronephrosis: swelling of kidney
What condition is associated with abnormal glucose values during pregnancy?
GDM
What is the body’s response to slightly alkaline state caused by mild hyperventilation?
renal compensation occurs where kidneys excrete increased amount of HCO3 (sodium bicarbonate) to reduce alkalosis and bring pH close to normal
How much more O2 is needed to support changes in mum’s body and growing fetus?
20% more
