Physiology in Pregnancy Flashcards
Why does the body change during pregnancy?
- Metabolism increases due to presence of foetus and placenta
- Aids foetal growth and development
- Adequate stores of energy and substrates
- Needs for transition to extra-uterine life
- Energy and substrate stored for the demand in pregnancy, labour and lactation
Give 8 characteristics of pregnancy
- Increased anabolism in 1st half
- Increased blood volume
- Weight gain
- Increased food intake and appetite
- Decreased activity
- Fat deposit about 3.5kg
- New protein synthesis (900g)
- Increased catabolism in 2nd half of pregnancy - stored fat used, increased insulin resistance and serum glucose
Give some endocrine changes that occur in pregnancy
- Insulin sensitivity, then insulin resistance
- Thyroid; relative iodine deficiency
- Levels of erythropoietin increase by 3x initial volume
- Facilitated progesterone, prolactin and hPL sustained through
Give some pituitary-adrenal changes that occur in pregnancy
- Pituitary gland enlarges
- Increased prolactin secretion
- Increase in ACTH from placenta
- Suppressed FSH and LH
- Increase in ADH, aldosterone and parathyroid hormone
Give some cardiovascular changes that occur in pregnancy
- High cardiac output
- Increase in vascular wall thickness and mass
- Vasodilation - increased blood flow to uterus
- Plasma volume increases
- High cholesterol
- Increase in triglycerides
- Haemostasis
What is the effect of plasma volume increasing?
Causes hypervolemia (too much fluid in blood) and haemodilution which can lead to physiological anaemia
How does RBC mass change during pregnancy?
- Increases
- Rate determines by tissue and foetal oxygen demand
- Increases more in multiple pregnancy
- Decreased oxygen supply to tissue triggers kidney to produce erythropoietin which can lead to erythropoiesis
- Increase RCV (red cell vol.) begins at end of 1st trimester
Describe how cardiac output changes in pregnancy
- Increase by 1.5l/min in first 12 weeks
- Mean increase = 6.61-7.71l/min
- Peak level reached between 20/40 and 26/40
- Increased blood vol, CO and decreased BP can cause breathlessness, palpitations and fainting
Describe the relationship between cardiac output, stroke volume and BP in pregnancy
- Increased HR
- Increased stroke vol
- Decreased peripheral resistance
- Diastolic BP decreases in first 2 trimesters
- Most women experience a 10% decrease in BP when they lie down
- Decreased BP in 2nd trimester; systolic by 5-10mmHg, diastolic by 10-20mmHg
Give figures to represent the blood flow in non-pregnant and pregnant women
Pulmonary = 5880ml (NP) 8330 (P) Peripheral = 2ml (NP) 7ml (P) Renal = 880 (NP) 1200 (P) Uterine = 51.7 (NP) 185 (P)
How does haemostasis (stopping a flow of blood) occur in pregnancy?
- Increased clotting factors
- Risk of DVT increased by 6x
- Impaired fibrinolysis
- Decreased plasmin and coagulation inhibitors
- Central to maintenance of balance between clot formation and its dissolution
- Coagulation system activated in pregnancy
What is the average blood loss per person?
Singleton = 500ml
Multiple pregnancy = 1000ml
What hepatic changes occur in pregnancy?
- Increased liver function
- Increased fibrinogen and transferrin
- Decreased serum albumin levels
- Decreased bilirubin
What respiratory changes occur in pregnancy?
- Increased oxygen consumption
- Increased carbon dioxide output
- Hyperventilation in contractions causes decrease in PaCO2
- Uterus pushes up diaphragm during labour and mucous membranes and nasal capillaries swell
- Pulmonary ventilation rate increases by 40%
- Residual volume decreases by 20%
- Tidal volume increases 500 - 700ml
What renal changes occur in pregnancy?
- Haemodynamic blood flow (80%)
- Glomerular filtration rate (50%)
- Increased renin, aldosterone, ADH and oestrogen
- Retention of salt and water