Repro 8.2 Maternal Physiology Adaptations in Pregnancy Flashcards
What problems are commonly associated with pregnancy?
Anaemia
Gestational diabetes
Hypertensive disorders
What tests are done in antenateal screening?
History and examination for risk factors
Blood tests - blood group, haemoglobin, infection
Urinalysis - protein
What cardiovascular changes occur with pregnancy?
Increased blood volume -> relationship with cardiac output and stroke volume and heart rate so they all also increase
Systemic vascular resistance decreases
Blood pressure initially decreases but returns to normal by T3
Why does BP initially decrease in pregnancy?
Progesterone effects on smooth muscle decrease resistance
Why does BP return to normal in T3?
Aortocaval compression by gravid uterus
Why is endothelium important in pregnancy?
Controls vascular permeability and contributes to the control of vascular tone
What is pre-eclampsia?
Defect in placentation, poor ureteroplacental circulation and widespread endothelial dysfunction
Vasoconstriction and plasma-contraction
What changes occur in the urinary system in pregnancy?
Glomerular filtration rate increases
Renal plasma flow increases
Filtration capacity intact
Functional renal reserve decreases as GFR increases
What effects do the renal changes have on serum concentrations of waste materials?
Increased GFR decreases serum concentrations of urea, uric acid, bicarbonate and creatinine
What are the normal pregnancy ranges for urea and creatinine?
Urea - 3.1mmol/L (decrease by 50%)
Creatinine - 25-75micromol/L
What complications might arise due to changes in the urinary system?
Urinary stasis - progesterone effect on urinary collecting system -> hydroureter or from obstruction
Increased risk of UTI (pyelonephritis may cause requirement of pre-term labour
What anatomical changes in the respiratory system result?
Diaphragm displaced A-P and transverse diameters of thorax increase Intercostal angle widens (mechanical limitations from uterus) Physiological change also occur
What are the consequences of changes in the resp system?
Decreased functional residual capacity
Vital capacity and total lung capacity relatively unchanged
Increased minute and alveolar ventilation
Increased tidal volume
RR unchanged
Why do many women experience physiological hyperventilation during pregnancy?
Increased metabolic CO2 production
Increased resp drive effect of progesterone
Resulting in resp alkalosis compensated by increased renal bicarbonate excretion and changes in sensitising chemoreceptors to CO2 changes
What causes the physiological dyspnoea in pregnancy?
Progesterone-drivne hyperventilation
At what stage of pregnancy does functional residual capacity change?
At T3 it decreases
How does carbohydrate metabolism change during pregnancy?
Pregnancy increases maternal peripheral insulin resistance - switches to gluconeogenesis and alternative fuels
This is achieved by human placental lactogen (hPL) also by prolactin, oestrogen/progesterone and cortisol
How does maternal blood glucose change?
Decrease in fasting blood glucose
Increase in post-prandial blood glucose
What is gestational diabetes?
Carbohydrate intolerance first recognised in pregnancy and not persisting after delivery
What risk factors are associated with poor control of gestational diabetes?
Macrosomic foetus (glucose stored as fat) Stillbirth Increased rate of congenital defects (eg. foetal liver enlarges due to glycogen storage)
How is gestational diabetes tested for?
Oral glucose tolerance test
What are the risk factors for developing gestational diabetes?
Family history of type 2 diabetes
Obesity
PCOS
Previous gestational diabetes or pregnancy problems
How does lipid metabolism change during pregnancy?
Increase in lipolysis from T2
Increase in plasma free fatty acids on fasting (free fatty acids provide substrate for maternal metabolism, leaving glucose for the foetus
Why is pregnancy associated with an increased risk of ketoacidosis?
Blood glucose falls as the foetus uses it. Lipids are used for maternal metabolism
How does thyroid activity change during pregnancy?
Thyroid binding globulin production increased
T3 and T4 increased but free T4 is in the normal range
Why does pregnancy result in increased thyroid activity?
hCG has a direct effect on thyroid stimulating thyroid hormone production
What anatomical changes occur in the GI system in pregnancy?
Alteration in the disposition of the viscera e.g. appendix moves to RUQ as uterus enlarges
What physiological changes occur in the GIT during pregnancy?
Smooth muscle relaxation by progesterone:
Delayed emptying
Stasis in the biliary tract
Increased risk of pancreatitis
What makes pregnancy prothromobtic?
Fibrin deposition at the implantation site
Increased fibrinogen and clotting factors
Reduced fibrinolysis
Stasis and venodilation also contribute
What are the consequences and problems with pregnancy being a prothrombotic state?
Thromboembolic disease in pregnancy may result
But warfarin crosses the placenta and is teratogenic
How does anaemia arise in pregnancy?
Plasma volume increases, as does red blood cell mass but not by as much -> physiological anaemia as concentration is diluted
However anaemia due to Fe- and folate deficiency can occur
Also haemoglobinopathies
What affects does pregnancy have on the immune system?
Foetus is an allograft
Non-specific suppression of the local immune response at the maternofoetal interface
Transfer of antibodies can cause haemolytic disease in the foetus or Graves disease and Hashimoto’s thyroiditis may result from antibody transfer
How does the insulin response to meals change in pregnancy?
Increased insulin released following a meal
How does progesterone affect appetite in the first half of pregnancy?
Stimulates appetitie and diverts glucose into fat synthesis
What causes the maternal increased resistance to insulin?
Hormones
How does the maternal circulation accommodate for the increased demand of the foetal-placenta unit during pregnancy?
Maternal vascular neogenesis. Accommodated for by changes in function of the maternal baro and volume receptors
What might result because of the reduced blood pressure and vasodilation in pregnancy?
'Feeling the heat' Easy to sweat Nasal congestion Postural hypotension Dizziness
Why does venous distension and engorgement occur in pregnancy and what can result from it?
Lack of sm contraction in venous walls -> reduced pressure in veins allows blood to pool due to gravitational effects
Mechanical pressure from the uterus compressing the IVC may increase lower limb venous pressure but only when mother is recumbent
What are the 2 long term sequelae that are attributed to this period of venous distension?
Varicose veins
Haemorrhoids
How is the expected sodium loss due to increased GFR compensated for?
Increased release of renin, aldosterone and angiotensin II
What affects can the position of the uterus have on the kidneys?
It can rest on the ureters compressing them above the pelvic brim, causing:
Increased intrauterine tone
Urethral dilation
Hydroureter
Hydronephrosis
This may also be caused be the effects of progesterone on sm
Why is pregnancy associated with an increased risk of urinary incontinence?
Uterus is superior and posterior to the bladder - pressure causes incontinence
Engagement of foetal head towards the end of pregnancy
What is the required uptake of Ca during pregnancy?
170% of normal
How is the increased requirement for Ca met?
Placenta contributes to maternal synthesis of DHCC (active form of fit D) which increases the ability to absorb Ca
T1 from gut
T2 from renal uptake
T3 PTH rises enhancing calcium mobilisation from maternal bone increasing availability to foetus
Why should blood blood pressure not be measured lying down in pregnancy?
Compresses IVC reducing venous return and hence lowering BP (supine hypotensive syndrome)
What is the expected heart rate in pregnancy?
80-90bpm
By how much does cardiac output increase in pregnancy?
40%
How much does tidal volume increase in pregnancy?
40%
How much does O2 consumption increase in pregnancy?
15%
Why might the neonate experience hypoglycaemia in gestational diabetes?
Increased foetal insulin secretion -> reflex hypoglycaemia when isolated from maternal glycogen stores
What congenital disorders might result from poorly controlled maternal diabetes?
Premature -> impaired lung maturation - resp disorders
Cardiac and neural tube defects and other congenital malformations may occur if conception occurs during a period of maternal hyperglycaemia
What symptoms might an anaemic mother experience?
May be asymptomatic
Tired
Dizzy
How is anaemia treated?
Oral iron sulphate or gluconate
Predict the consequences of poor foetal-placental perfusion associated with anaemia in pregnancy.
Increased risk of congenital defects (growth retardation)
Mortality in anaemic pregnancy increased x3-5
Still birth rate increases x6
How does smoking during pregnancy affect O2 flow to foetus?
Hb-O2 curve shift left
Less O2 bound to haemoglobin so less O2 to baby (CO instead)
What are the diagnostic criteria for pre-eclampsia?
Hypertension
Proteinuria
Oedema +/-
What treatment might need be given to the foetus if the mother has pre-eclampsia?
Steroids - the foetus may need to be delivered imminently - steroids accelerate foetal lung maturation. Close monitoring of foetal status needed
What signs suggest that mild pre-eclampsia is worsening in severity?
Increased diastolic BP Persistant and worsening albuminuria Oliguria Thrombocytopenia Elevated liver enzymes Lack of foetal growth Olighydraminos Pulmonary oedema Headache Visual complaints
What is eclampsia?
The onset of convulsions in a pregnancy complicated by pre-eclampsia
How would you treat a patient having an eclamptic fit?
Maintain airway and administer O2
Place her on her left side (enhance uterine perfusion)
Maintain her safety during convulsions
Mg given by IV bolus then continual infusion to relieve vasospasm and stop fitting
Sometimes thiopentone or diazepam needed for recumbent fits
BP control usually requires hydralazine
Once stable assess foetus and maintain optimum fluid/O2/position
Delivery is the only definitive treatment - C-section often required unless cervix is extremely favourable
What complications are associated with multiple pregnancies?
Anaemia Polyhyrdraminos Preterm labour Perinatal mortality Antepartum haemorrhage Increased incidence of pregnancy induced hypertension
