Maternal physiology Flashcards
What does the body need to adapt to pregnancy?
- Volume support (volume expansion and vasodilation)
- Nutrition (increased respiration, insulin resistance, increased absorption)
- Waste clearance (increased GFR and hepatocellular stimulation)
- Pregnancy maintenance (uterine quiescence and immunologic sequestration)
- Childbirth (MSK and clotting)
What drives the adaptations of the human body during pregnancy?
- Hormones e.g.
- hCG
- oestrogen
- progesterone
- relaxin
- hPL
Why does immunity change in pregnancy?
- Baby is a foreign object in mother’s body
- Need to avoid body rejecting baby
- Allows baby to thrive but as a parasite
- Allows mother to be a good host
What is meant by the statement: the foetus is a hemi-allograft?
- Recognised by maternal immune system
- Half of foetus is foreign to mother (1/2 mum’s genes and 1/2 dad’s
- SO incited allo-response is not cytotoxic
What happens to immunity in pregnancy?
- Immunosuppressed state
- Higher attack rate and severity of certain viral pathogens i.e. varicella
- May improve certain autoimmune conditions
What does mum need from respiration in pregnancy?
- Continued O2 delivery to her organs and periphery
- Increased O2 supply to meet metabolic demand
- Increased CO2 clearance
What does baby need from respiration in pregnancy?
- Oxygen delivery
- Carbon dioxide removal
How are the respiratory needs of mum and baby met during pregnancy?
- Increased ventilation
- Tidal volume increases by ~30-40%
- Minute ventilation increases by ~40-50%
- Increase PaO2, decrease PCO2
- pH change (respiratory alkalosis, compensated by renal bicarb excretion)
- Expiratory reserve volume decreases by ~20%
- Total lung capacity decreases by ~5%
What is the clinical consequence of respiratory changes that occur in mum during pregnancy?
- Dyspnoea of pregnancy occurs in 60-70% of patients
- Multifactorial
- Most likely due to hyperventilation and decreased PaCO2
What else could cause dyspnoea in a pregnant woman?
- Cardiac pathology
- Anaemia
- DVT/PE
- Asthma
- Pneumonia/ARDS
- Pulmonary oedema
What does baby need from the cardiovascular system and the blood?
- Delivery of nutrients
What does a pregnant mum need from the cardiovascular system and the blood?
- Needs to fill utero-placental-foetal circulation
- Oxygenate growing uterus - very vascular and high demand
- Protect from impaired venous return
- Prepare for potential blood loss during delivery
How are the changes to the cardiovascular system and the blood achieved during pregnancy?
- Volume expansion
- Clotting mechanisms
How is volume expansion of the cardiovascular system during pregnancy achieved?
- In early pregnancy volume increases
- In late pregnancy heart rate increases
- Progesterone causes smooth muscle relaxation
- Decreased systemic vascular resistance
- Drop in BP (but then returns to pre-pregnancy level)
How is increased clotting of the cardiovascular system during pregnancy achieved?
- Increased procoagulants (fibrinogen, factor VIII, vWF)
- Decreased anticoagulants (e.g. Protein S)
- Reduced fibrinolysis
How is stroke volume increased in pregnancy?
- Oestrogen and progesterone activates RAAS
- Oestrogen also activates release of angiotensin from liver
What are the consequences of pregnancy on the cardiovascular system?
- Increased RAAS leads to peripheral oedema
- Change in plasma volume leads to change in RBC volume
- Dilutional oedema
- Clotting leads to hypercoagulable state - increased number of thromboembolic events
What are the values that define anaemia in pregnancy?
- 1st trimester Hb <110 g/l
- 2nd and 3rd trimester: <105 g/l
- Postpartum <100 g/l
- Normal Hb: 115-165 g/l
Why does anaemia of pregnancy occur?
- Red cell mass increases by 25-30%
- Not enough to counter dilutional increase in plasma volume
- Iron deficiency is a problem despite relative macrocytosis
- Most common cause of anaemia in pregnancy is iron deficiency
What are the complications of anaemia of pregnancy?
- Increased morbidity for mum and baby
- Preterm delivery
- Maternal fatigue
- Infant iron deficiency anaemia
What does the baby need from the renal system during pregnancy?
- Remove waste
What does the mum need from the renal system during pregnancy?
- Increase clearance of waste at the kidneys
What changes occur to the renal system during pregnancy?
- Increased glomerular filtration rate
How do renal haemodynamics change in pregnancy?
- Systemic vasodilation leads to increased renal blood flow
- This increases GFR by 50%
- Afferent and efferent arteriole vasodilation
- Decreases serum urea and creatinine
How does tubular function change in pregnancy?
- PCT absorption decreases
- Leads to increased glycosuria
- Increased Ca2+ excretion
- Increased glycosaminoglycans
- Decreased reabsorption of uric acid
What systemic changes occur to the kidney in pregnancy?
- Decreased sensitivity to RAAS
- Increased water retention (hypothalamus has a lower threshold for vasopressin)
- Decreased plasma osmolality
What systemic changes occur to the kidney in pregnancy?
- Decreased sensitivity to RAAS
- Increased water retention (hypothalamus has a lower threshold for vasopressin)
- Decreased plasma osmolality
What structural changes occur to the kidney during pregnancy?
- Increased size of kidneys and ureters
- Right > left
- Decreased speed of urine passage
- Hydronephrosis
What does baby need from the GI system during pregnancy?
- Nutrients
What does mum need from the GI system during pregnancy?
- Feed herself and her baby
- Increase absorption of minerals and vitamins
What adaptations occur in the GI system during pregnancy?
- Slow transit time
What are the effects of progesterone on the GI system?
- Decreased lower oesophageal sphincter tone - leads to GORD and aspiration
- Decreased gallbladder contractility - leads to gallstones
- Decreased large and small bowel motility - leads to increased mineral absorption, constipation and increased water absorption
What structural changes occur to the GI system in pregnancy?
- Gravid uterus displaces bowel
- Can cause mechanical obstruction
How do LFT values change during pregnancy?
- ALP levels increased due to placental synthesis
What does baby need from the endocrine system during pregnancy?
- Nutrients
- A good environment
What does mum need from the endocrine system during pregnancy?
- A way to give glucose to baby
- A lot of calcium
- Keep metabolism under control
How does the endocrine system change during pregnancy?
- Thyroid regulation
- Parathyroid activation
- Insulin resistance
How does the thyroid gland adapt to pregnancy?
- Pregnancy is considered a euthyroid state
- Imbalanced levels can affect foetal development
- Oestrogen stimulates liver to produce Thyroid Binding Globulin
- Need to increase thyroxine production
- hCG has a similar alpha subunit to TSH
- So it has a weak stimulating effect on thyroid
How do PTH and calcium levels change in pregnancy?
- Increased PTH leads to increased active vitamin D
- Increases Ca2+ and phosphorus absorption from gut during pregnancy
- Bones do not resorb Ca2+ and phosphorus
- Decreased PO4 excretion by kidneys and increased Ca2+ absorption at kidneys
- Due to increased 1 alpha-hydroxylase
What are the pre-pregnancy determinants of insulin resistance?
- Ethnicity
- Physical inactivity
- Obesity
- Dietary composition
- Polycystic ovarian syndrome
- Hypertension
What causes insulin resistance in pregnancy?
- Tumour necrosis factor a
- Placental lactogen
- Placental growth hormone
- Oestrogen
- Progesterone
- Cortisol
What are the risk factors for gestational diabetes mellitus?
- BMI above 30 kg/m2
- Previous macrosomic baby weighing 4.5kg+
- Previous gestational diabetes
- Family history of diabetes
- Ethnicity with high prevalence of diabetes
What are the investigations/diagnosis of gestational diabetes mellitus?
- Oral glucose tolerance test to test for gestational diabetes in women with risk factors
- Blood glucose or OGTT if previous gestational diabetes mellitus
- Diagnose if plasma glucose 5.6 mmol/l or above
- A 2 hour plasma glucose level of 7.8 mmol/l or above
What are the potential complications of gestational diabetes for the mother?
- Increased risk of pre-eclampsia, polyhydramnios, premature labour
- Shoulder dystocia
- Failure for labour to progress
- Increased risk of developing Type 2 diabetes mellitus
What are the potential complications of gestational diabetes for the baby?
- Macrosomia
- Congenital abnormalities (cardiac, renal, neural tube defects)
- Hypoxia and sudden intrauterine death after 36 weeks gestation
- Hypoglycaemia
- Respiratory distress
- Jaundice
What changes occur in MSK and skin during pregnancy to help the baby?
- Room to grow
- A way out
What changes occur in MSK and skin during pregnancy to help the mum?
- Cope with additional weight
- Cope with change in centre of gravity
- Prepare body for childbirth
How does MSK and skin change during pregnancy?
- Everything becomes loose and stretchy
What MSK-related symptoms does a woman experience during pregnancy?
- Back pain
- Shoulder pain
- Tension headaches
- Pelvic pain
What adaptations occur to the MSK system during pregnancy?
- Change in centre of gravity due to increased lordosis and kyphosis and forward flexion of neck
- Stretching of abdominal muscles impede posture and strain paraspinal muscles
- Increased motility of sacroiliac joints and pubic symphysis causes anterior tilt of pelvis
What changes can be seen in the skin during pregnancy?
- Chloasma
- Palmar erythema
- Vascular spiders
- Linea nigra
What changes can be seen in the skin during pregnancy?
- Chloasma
- Palmar erythema
- Vascular spiders
- Linea nigra
What is pre-eclampsia?
- Pregnancy-induced hypertension with proteinuria +/- maternal organ dysfunction after 20 weeks
What is the NICE definition of pre-eclampsia?
- New onset of hypertension (>140/90) after 20 weeks
- And the co-existence of 1 or more of the following new-onset conditions:
- Proteinuria
- Other maternal organ dysfunction
- Uteroplacental dysfunction
What is severe pre-eclampsia?
- Pre-eclampsia with severe hypertension that does not respond to treatment
What is the pathogenesis of pre-eclampsia?
- Impaired invasion of trophoblast leading to shallow invasion of spiral arteries
- Remain small calibre and of high resistance
- Leads to hypoperfusion and ischaemia
- Systemic endothelial dysfunction
What are the symptoms of pre-eclampsia?
- Headache
- Vision disturbance (blurring/flashing)
- Epigastric pain
- Swelling of hands, feet, face
- Vomiting
- SOB
What are the maternal complications of pre-eclampsia?
- Seizure
- Cerebral haemorrhage
- Renal failure
- Pulmonary oedema
- HELLP syndrome (haemolysis, elevated liver enzymes, low platelets)
- DIC
What are the foetal complications of pre-eclampsia?
- Growth restriction
- Oligohydramnios
- Placental infarct
- Foetal distress
- Premature delivery
- Stillbirth
