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
What gastrointestinal changes occur in pregnancy?
- Smooth muscle relaxation
- Mechanical displacement of organs
- Total protein and albumin in liver decrease
- Cholesterol and triglycerides in liver increase
What musculoskeletal changes occur in pregnancy?
- Relaxation of pelvic joints
- Increased calcium requirement and absorption due to foetal demands and storage in preparation for lactation
- Weight gain leading to altered posture (lordosis)
- Loss of abdominal muscle tone
What reproductive changes occur in pregnancy relating to the uterus?
- Hypertrophy and hyperplasia
- 20x increase in cellular mass and 1000x increase in intrauterine volume
- Uterus at term = 30x23x20cm
- Uterine walls thicken and muscle cells grow
What reproductive changes occur in pregnancy relating to blood flow?
- Uterine arterial blood flow 50ml/m - 600ml/m
- Pelvic venous capacity increase x60
- Uteroplacental blood flow system contains 1000ml of blood in late pregnancy
What reproductive changes occur in pregnancy relating to the reproductive organs?
- Breasts enlarge and glandular tissue develops
- Breasts become vascularised (increased capillaries)
- Cervix increases in mass and width
- Vaginal tissue softens
- Increased vaginal discharge due to increase venous blood flow and cervical mucous
What immunological changes occur in pregnancy?
- Placental barrier
- Mean WBC count increases
- Erythrocyte sedimentation rate increases due to increased fibrinogen
What skin changes occur in pregnancy?
- Hyperpigmentation
- Oestrogen and progesterone are melanogenic stimulants
- Hair growth increases
- Hair falls out postpartum
How does nausea and vomiting affect women in pregnancy?
- NVP = nausea and vomiting in pregnancy
- Common particularly in 1st trimester
- No definite cause but linked to effect of progesterone on gastric smooth muscle and delayed gastric emptying
What advice should be given to pregnant women experiencing nausea and vomiting?
- Rest
- Consume frequent, small meals rich in easily digested carbohydrate and low in fat
- Meat and strong smells make nausea worse
What is hypervolemia?
Too much fluid in the blood
How is hypervolemia beneficial to the mother and foetus
- Increased cardiac output
- Increased blood volume
- Rise in plasma volume relative to RBC mass (haemodilution)
- Hypervolemia + Haemodilution = Physiological anaemia
- Haemodilution causes reduced viscosity of blood
- Less resistance and less cardiac force required
- Increased placental perfusion (blood flow)
What are the positive effects of increased placental perfusion?
- Reduced risk of pre-eclampsia
- Increased blood flow to skin
- Increased plasma volume
- Increased blood flow and clotting factors guard against excessive blood loss in labour
How is increased blood flow to the skin beneficial?
Eliminates excess heat and kidneys can cope with increased waste products
How is increased plasma volume beneficial?
Provides fluid reserve for modifying effect of blood loss during childbirth and stabilises reduction in blood volume during delivery
What is peripheral resistance?
Resistance that blood encounters as it travels through the blood vessels (opposite of BP)
How is constipation caused in pregnancy?
- Relaxation caused by progesterone
- Slow movement of food
- More water absorbed
- Harder stools
- Constipation
