Repro16 - Maternal Physiology

Question 1

5 endocrine changes during pregnancy

T3/T4 Levels
Importance of Thyroxine (T4)
Insulin Resistance
Switch in Energy Source
Parathyroid Hormone (PTH)

Answer 1

1. ) Rise in Total T3 and T4 Levels - oestrogen –> more thyroid binding globulin (TBG) which binds to free T3/T4
   - AP releases more TSH leading to increase in T3/T4
   - free T3/T4 remains the same but total T3/T4 increases
2. ) Thyroxine (T4) Production - essential for neural development in the foetus in early development
   - foetal thyroid gland not functional until 2nd trimester
   - rise in T3/T4 levels ensures high levels of thyroxine
3. ) Increased Insulin Resistance - oestrogen and progesterone causes a rise in anti-insulin hormones
   - reduction of maternal peripheral uptake of glucose ensures continous supply of glucose for the fetus
   - hormones: hPL, prolactin, cortisol
4. ) Switch in Energy Source - mother turns to using lipids to preserve glucose for the foetus
   - increase in lipolysis –> increase in free FAs in plasma provides substrate for maternal metabolism
   - lipid breakdown can can lead to ketogenesis meaning pregnancy increases risk of ketoacidosis
5. ) Rise in PTH - releases Ca2+ ions for the fetus
   - mother requires adequate dietary intake of calcium so only minimal bone resorption occurs

Question 2

3 cardiovascular changes during pregnancy

Blood Pressure
Cardiac Output
Blood Volume

Answer 2

1. ) Decrease in Diastolic BP - progesterone decreases systemic vascular resistance
   - occurs during the 1st and 2nd trimester
   - rise in BP could indicate pre-eclampsia
2. ) Increase in Cardiac Output - increases by 33-50%
   - response to fall in BP
   - early pregnancy due to increase in stroke volume
   - late pregnancy due to increase in heart rate
3. ) Increase in Blood Volume - oestrogen and progesterone causes activation of RAAS
   - increases sodium levels and water retention
   - can lead to peripheral oedema

Question 3

3 respiratory changes during pregnancy

Total Lung Capacity
Tidal Volume
Ventilation

Answer 3

1. ) Maintained Total Lung Capacity - only down by 5%
   - fetus causes elevation of the diaphragm
   - increase in transverse and AP diameters of the thorax maintains the TLC
2. ) Increased Tidal Volume - increases by 30-40%
   - helps mother meet increase in O2 demand caused by an increase in metabolic rate
   - causes decrease in expiratory residual volume by 20%
3. ) Hyperventilation - progesterone produces increased CO2 production and increased respiratory drive
   - respiratory alkalosis compensated by increased renal HCO3- excretion is normal during pregnancy
   - can lead to shortness of breath (dyspnea)

Question 4

5 gastrointestinal changes during pregnancy

Intra-Gastric Pressure
Lower Oesophageal Sphincter Tone
Appendix
Gut Motiltiy
Gallbladder

Answer 4

1. ) Raised Intra-Gastric Pressure - due to gravid uterus causing upwards displacement of the stomach
   - can lead to GORD, nausea and vomiting
2. ) Decreased Lower Oesophageal Sphincter Tone
   - caused by progesterone relaxing smooth muscle
   - also leads to GORD but also aspiration
3. ) Appendix Location - can move to the RUQ
   - due to enlargement of the gravid uterus
4. ) Decreased Gut Motility - progesterone causes SM relaxation, allowing more time for absorption
   - can lead to constipation
5. ) Gallbladder Relaxation - progesterone causing smooth muscle relaxation –> biliary tract stasis
   - this predisposes the mother to gallstones

Question 5

5 urinary changes during pregnancy

GFR
2 Ureter
2 Bladder

Answer 5

1. ) Increase in GFR - increased by 50-60%
   - caused by increase in CO and renal blood flow
   - leads to an increase in renal excretion and decreased PCT absorption –> glycosuria
   - so in pregnancy, lower levels of urea and creatinine
2. ) Ureter Relaxation –> hydroureter (ureter dilation)
   - due to progesterone causing SM relaxation
   - leads to urinary stasis –> increased risk of UTIs
3. ) Ureter Compression - caused by gravid uterus
   - causes backflow of urine which can lead to swelling of the kidneys (hydronephrosis)
4. ) Bladder Muscle Relaxation - progesterone
   - leads to urinary stasis –> increased risk of UTIs
5. ) Bladder Compression - caused by gravid uterus
   - increases intravesical pressure which can lead to urinary incontinence

Question 6

5 haematological changes during pregnancy

Clotting
Veins
Thromboembolic Events
2 Causes of Anaemia

Answer 6

1. ) Increased Clotting - oestrogen makes liver make more clotting factors
   - also increase in fibrinogen and decrease in fibrinolysis
   - increases risk of thromboemoblic events
2. ) Venodilation - caused by progesterone
   - increased stasis –> risk of thromboembolic events
3. ) Management of Thromboembolic Events
   - wafarin cannot be given as it is a teratogen
   - low molecular weight heparin (LMWH) is given if the mother needs an anticoagulant
4. ) Iron Deficiency - although the mother has less periods (less iron loss), the fetus still requires so much iron –> iron deficiency
   - leads to iron deficiency anaemia
5. ) Dilutional Anaemia - significant increase in plasma volume due to effect of RAAS
   - only small increase RBCs –> reduced haematocrit

Question 7

MSK and skin changes during pregnancy

Center of Gravity
Abdominal Muscles
Pelvic Pain
Structure Compression
Pigmentation x4

Answer 7

1. ) Center of Gravity Shifts Forwards - due to:
   - increased lordosis and kyphosis
   - foward flexion of the neck
   - causes back pain, shoulder pain, tension, headaches
2. ) Stretching of Abdominal Muscles
   - impedes posture and strains paraspinal muslces
   - causes back pain, shoulder pain, tension
3. ) Pelvic Pain - caused by the increased mobility of sacroiliac joints and pubic symphysis
   - anterior tilt of the pelvis

4.) Compression of Structures - fluid retention can compress structures such as the median nerve (carpal tunnel syndrome)

5. ) Hyperpigmentation - caused by increase in MSH
   - cholasma/melasma (mask of pregnancy)
   - palmar erythema, vascular spiders, linea nigra

Question 8

4 features of pre-eclampsia

What is it?
Aetiology
Maternal Complications x6
Fetal Complications x4

Answer 8

1. ) What is it? - multisystem pregnancy disorder characterised by hypertension (new onset) + proteinuria
   - usually presents in 3rd trimester
   - resolves after delivery but can occur postpartum
2. ) Aetiology - impaired implantation
   - shallow invasion of spiral arteries so they remain spiral and high resistance –> hypoperfusion and ischaemia
3. ) Maternal Complications - seizures (eclampsia)
   - cerebral bleeding, renal failure, pulmonary oedema
   - DIC and thrombocytopenia
   - hepatic failure or rupture (rare)
4. ) Fetal Complications
   - growth restriction due to reduced blood flow
   - oligohydramnios (low levels of amniotic fluid)
   - placental infarct or abruption
   - fetal distress –> premature delivery –> stillbirth

Question 9

Diagnosis/management of pre-eclampisa

Risk Factors
Signs and Symptoms of Mild Pre-eclampsia x4
Signs and Symptoms of Severe Pre-eclampsia x4
Examinations x2
Management

Answer 9

1. ) Risk Factors - age (extremes), obesity, diabetes
   - history of pre-eclampsia (family or prior pregnancy)
   - first pregnancy, multiple gestation, IVF
   - chronic or gestational hypertension
   - pre-existing renal disease
2. ) Signs and Symptoms of Mild Pre-eclampsia
   - hypertension, proteinuria, weight gain, oedema
3. ) Signs and Symptoms of Severe Pre-eclampsia
   - headaches, blurred vision, nausea/vomiting, abdominal or back pain
4. ) Examinations
   - optic fundi: papillloedema suggests cerebral oedema
   - tendon reflexes: hyper-reflexia due to brain damage
5. ) Management
   - stabilise BP, fluid restriction, monitor urine output
   - MgSO4 for neuroprotection and to prevent seizures
   - deliver the baby early if needed