Maternal Physiology (Pregnancy) Flashcards
What is the purpose of maternal cardiovascular changes occurring with pregnancy?
Improve foetal oxygenation and nutrition
What are the CV anatomic changes of pregnancy?
-heart displaced upward and to left
-heart assumes more horizontal position (apex moved laterally)
-ventricular muscles mass increase (due to inc in circulating blood volume)
Occur due to diaphragmatic elevation by enlarging uterus
What is the primary functional change of CV system with pregnancy?
Increase in CO
How much does CO increase with pregnancy?
30-50%.
50% of increase in first 8 weeks
what is the mechanism of increased CO during pregnancy?
- First half: due to inc SV
- Second half: inc HR (SV returns normal)
What causes the alterations in stroke volume?
Alterations in circulating blood volume and systemic vascular resistance
When is the peak increase in blood volume during pregnancy?
Peak of 45% increase at 32 weeks
Why does systemic vascular resistance decrease?
- Progesterone relaxing SM
- Inc production of vasodilators (PGs, NO, ANP)
- Arteriovenous shunting to uteroplacental circulation
What may cause a decrease in CO during pregnancy?
Venous return to heart being impeded by venal caval obstruction by enlarging gravid uterus
What is the path of venous return from lower extremities in the setting of complete vena caval obstruction in term pregnancy?
Dilated paravertebral collateral circulation
How does maternal HR change in pregnancy?
Increases as pregnancy progress.
Increases 10-18bpm over non pregnant value by term
What happens to dBP with pregnancy?
Decreases begin in 7th week; maximal decrease of 10mmHg by 24-32 weeks
What is inferior vena cava syndrome?
10% women have symptoms of: -dizziness -light headedness -syncope when lying supine. May be due to insufficient shunting by paravertebral circulation when gravid uterus occludes IVC
What are the normal CV PEx findings during pregnancy?
- Increased S2 split with inspiration
- Distended neck veins
- Low grade systolic ejection murmur (? due to increased flow across aortic and pul valves)
- Many have S3 gallop
What is the primary mediator of the respiratory changes occurring with pregnancy?
Progesterone
How does oxygen consumption change with pregnancy?
20% increase (50mL/min)
How is the increased oxygen consumption utilised within the pregnant body?
Ff the increase:
- 50% used by uterus and contents
- 30% heart and kidneys
- 18% respiratory muscles
- remainder to mammary tissues
What is the primary respiratory parameter changed with pregnancy?
30-40% increase in minute ventilation
What are the results of the increased minute ventilation?
Changes in acid-base
- progesterone sensitises central chemoreceptors to CO2 -> increased respiration and decreased arterial PCO2
- respiratory alkalosis compensated by renal excretion of bicarbonate
What causes the dyspnoea of pregnancy?
Physiologic response to low arterial PCO2
URT changes pregnancy
- allergy like symptoms or chronic colds
- mucosal hyperemia producing nasal stuffiness and increased nasal secretions
What do ABGs in pregnancy usually show?
Compensated respiratory alkalosis
What are the haematologic changes of pregnancy?
- increase in plasma volume
- increase in red cell volume
- increase in coagulation factors
When does maternal plasma volume peak?
30-34 weeks then stabilises
What is the mean plasma volume increase?
- 50% singleton
- Greater if multiple
What is the maternal blood volume increase with pregnancy?
35% by term
What is the total additional iron requirement during pregnancy?
Additional 1000mg
- 500mg to increase red cell mass
- 300mg to foetus
- 200mg to compensate for iron loss
What is the recommended daily iron need in a pregnant woman who is not anemic?
60mg
How do WBCs change during pregnancy?
- Mild increase throughout
- More pronounced increase in labour: primarily increased granulocytes linked with stress induced demargination (cf disease associated inflammatory response)
How do clotting factor concentrations change with pregnancy?
-FI (fibrinogen) 50% increase
-VII, VIII, IX, X 50% increase
-Promthrombin (II), V, VII unchanged
Inhibitors of coagulation (protein C and S) both decrease
What are the functional changes of erythrocytes during pregnancy?
Enabled enhanced oxygen uptake in lungs inc delivery to foetus and CO2 exchange
- significant increase in total oxygen carrying capacity
- Bohr effect (due to comp resp alkalosis) shifts O2 dissociation curve to left
- M lung O2 affinity increases
- Placental CO2 (F:M) gradient inc -> facilitates transfer to mother
Why is there a physiologic anaemia of pregnancy?
Disproportionate increase in plasma volume cf red cell volume (dec in Hb and haematocrit)
What is the primary anatomic change of the renal system in pregnancy?
Enlargement and dilation of kidneys and urinary collecting system largely due to increased renal plasma flow
How does GFR change with pregnancy?
Increases to 50% over non pregnant state; at term may be up to 75%
Why is urinary glucose excretion common (i.e. nearly all) in pregnant patients?
Increased GFR results in increased load of solutes presented to renal system.
Symptoms of changes to renal physiology with pregnancy?
- Urinary frequency due to bladder compression
- Stress urinary incontinence
- urinary stasis predisposes to pyelonephritis in pts with asymptomatic bacteriuria
What are the GIT anatomic changes of pregnancy?
- Displacement of stomach and intestines due to enlarging uterus
- Increase in portal blood flow
What are the functional change of the GIT during pregnancy?
Generalised SM relaxation due to progesterone produces: -lower oesophageal sphincter tone -decreased GIT motility -impaired GB contractility Leading to: -Significantly increases transit time -GORD -Increased prevalence gallstones, cholestasis
What effect does pregnancy have on hepatic biosynthesis?
Oestrogen increases biosynthesis of:
- fibrinogen
- ceruloplasmin
- binding proteins for:
- corticosteroids
- sex steroids
- thyroid horones
- vitamin D
GIT symptoms of pregnancy?
- NVP (4-8w - 14-16w)
- Increased energy requirements
- Cravings
- GORD
- Constipation
- Generalised pruritus?
What causes NVP?
Unknown; related to increased
- progesterone
- hCG
- relaxation of SM of stomach
PEx GIT findings of pregnancy?
- Gingivial disease
- Haemorrhoids
What is epulis gravidarum?
Violaceous, pedunculated lesions occurring at gum line; pyogenic granulomas related to oedematous, soft gums of pregnancy.
Why does ALP increase?
Doubled mainly due to increased placental production
How does HCG affect thyroid?
Has thyrotropin like effect producing transient T4 increase in first trimester. Normalisation with decline of HCG after first trimester.
How does oestrogen affect thyroid balance?
Induces hepatic synthesis of TBG - increased T4 and T3 levels.
Free T3 and T4 (active) unchanged.
How does oestrogen affect cortisol?
Increases hepatic synthesis of cortisol binding globulin: inc levels of serum cortisol.
- serum cortisol increases progressively from first trimester until term.
- ACTH rises until term
What is the metabolic effect of pregnancy?
Diabetogenic effect: reduced tissue response to insulin, hyperinsulinemia, hyperglycemia.
Net effect: maternal response to glucose load is blunted producing post prandial hyperglycaemia.
Why does insulin resistance occur with pregnancy?
Mainly due to effect of human placental lactogen
What is the primary fuel of the foetus and placenta?
Glucose.
Hence maternal hypoglycaemia may occur during periods of fasting
Lipid changes of pregnancy?
Increased circulating concentrations of lipids, lipoproteins, apolipoproteins.
Fuel in cases of maternal hypoglycemia; characterised as accelerated starvation.
What causes ligament laxity in pregnancy?
Relaxin and progesterone
Calcium metabolism of pregnancy?
- Increased skeletal Ca mobilisation (total maternal calcium decreases)
- significant inc in PTH (maintains serum Ca: inc intestinal absorption, decreases renal loss)
- No loss of bone density (?protective effects of calcitonin)
Skin changes with pregnancy?
- Spider angiomata
- Palmar erythema
- Striae gravidarum
- Hyperpigmentation (?oestrogen, MSH)
- Chloasma / melasma
- Eccrine sweating and sebum production
