What are the constituents of antenatal screening?
- History and examination
- Blood test
What is being looked for in the history and examination stage of antenatal screening?
Risk factors, e.g. for gestational diabetes
What is being looked for in a blood test in antenatal screening?
- Rhesus incompatability
What rhesus incompatability is significant?
-ve mother with +ve fetus
Why is it important to intervene early when there is a rhesus incompatability?
To prevent this from preventing future pregnancies
Why should haemoglobin be tested in antenatal screening?
Because there is a risk of anaemia development in pregnancy due to the high iron demans of the fetus
Why is it important to check for infections in antenatal screening?
Because they can be tetragenic
Give two examples of infections it is important to check for in antenatal screening
Why is it important to check for syphilis in antenatal screening?
Can cause congenital defects
Why is it important to check for HIV in antenatal screening?
Concerns about vertical transmission
What should be checked for in urinalysis in antenatal screening?
What is the importance of proteinuria in antenatal screening?
Sign of pre-eclampsia, indicating systemic organ involvement as a result of maternal syndrome
What systems undergo physiological changes in pregnancy?
- Cardiovascular system
- Respiratory system
- Metabolic changes
- Gastrointestinal system
- Immune system
What happens to the cardiovascular system in pregnancy?
Many haemodynamic changes occur
When do the haemodynamic changes occur in pregnancy?
Why do the haemodynamic changes in pregnancy occur very early?
Strong anticipatory changes, reflective of the need to supply big utero-placental circulation, required for later need
By how much does the blood volume increase in pregnancy?
Why does the blood volume increase by 50% in pregnancy?
- Because there is a new circulation to support
- Have to increase blood flow to the kidneys
- Pre-empt blood loss at delivery
Why is there an increased blood flow to the kidneys in pregnancy?
Because mum's kidneys have to act for the fetus
How much blood loss is expected in a normal vaginal delivery?
How much blood loss is expected in a caeserian?
Is systolic BP increased in pregnancy?
What happens to blood pressure in T1 and T2?
Progesterone has effects on systemic vascular resistance, and so decreases BP
What is the result of the decreased blood pressure in T1 and T2?
Increased risk of vaso-vagal episodes
What happens in a vaso-vagal episode?
Nausea and feeling faint
What is the problem with the hypotension in T1 and T2 of pregnancy?
Can mask exisiting hypertension, which is a risk factor for pre-eclampsia
What can happen to blood pressure in T3?
May be aortocaval compression by gravid uterus, leading to hypotension
What causes a gravid uterus?
Significant hypertrophy of the myometrium and enlarged fetus
What should be considered due to aortocaval compression by a gravid uterus?
Shouldn't leave pregnant woman supine for a long time
Why shouldn't a pregnant woman be left supine for a long time?
Reduces perfusion to the placenta, and so decreases oxygen exchange
What is the important of the endothelium in pregnancy?
- Controls vascular permeability
- Contributes to the control of vascular tone
How does endothelium contribute to the control of vascular tone in pregnancy?
By signalling to smooth muscle
Is there normal vasodilation in pregnancy?
What is the difference in plasma volume between normal pregnancy and pre-eclampsia?
Plasma expanded in normal pregnancy, contracted in pre-eclampsia
What is the difference in vasodilation between normal pregnancy and pre-eclampsia?
Vasodilation in normal pregnancy, vasoconstriction in pre-eclampsia
Why does blood pressure increase in pre-eclampsia?
There is a big strain on the placenta, so not able to support fetus, so increase in BP to try and compensate
What is pre-eclampsia characterised by?
- Defect in placentation
- Poor uteroplacental circulation
- Widespread endothelial dysfunction throughout maternal CNS
What is pre-eclampsia a precursor to?
What is eclampsia?
Significant generalised seizures
What is the problem with eclampsia?
It is bad for the mother and baby, and so is an emergency situation
What happens to cardiac output in pregnancy?
When does cardiac output change in pregnancy?
What happens to stroke volume in pregnancy?
When does stroke volume change in pregnancy?
What happens to heart rate in pregnancy?
When does heart rate change in pregnancy?
What happens to systemic vascular resistance in pregnancy?
When does systemic vascualr resistance change in pregnancy?
What happens to blood pressure in pregnancy?
Decreases in T1 and T2, then returns to normal in T3
What changes occur in the urinary system in pregnancy?
- Glomerular filtration rate increases
- Renal plasma flow increases
What happens to filtration capacity in pregnancy?
It remains in tact
What happens to the functional renal reserve as GFR increases in pregnancy?
It decreases, as there is a limit as to how much the system can stretch
What are the consequences of the changes in the urinary system in pregnancy?
- Urinary stasis
What causes urinary stasis in pregnancy?
- Progesterones effect on the urinary collecting system
What does progesterones effect on the urinary collecting system in pregnancy cause?
What is urinary obstruction in pregnancy related to?
Are UTIs common in pregnancy?
What can UTIs lead to in pregnancy?
Pyelonephritis, which causes pre-term labour
What happens to RPF in pregnancy?
What happens to GFR in pregnancy?
What happens to creatinine clearance in pregnancy?
What happens to protein excretion in pregnancy?
+ up to 300mg/24hours
What happens to urea in pregnancy?
What happens to uric acid in pregnancy?
- 33%, but rises with gestation
What happens to bicarbonate in pregnancy?
What happens to creatinine in pregnancy?
What anatomical changes are there to the respiratory system in pregnancy?
- Diaphragm displaced
- A-P and transverse diameters of the thorax increases to compensate for the diaphragm
What are the consequences of the anatomical changes in the respiratory system during pregnancy?
- Decreased functional residual capacity
- Vital capacity unchanged, total lung capacity unchanged
What physiological changes are there to the respiratory system during pregnancy?
- Increased minute and alveolar ventilation
- Increased tidal volume
What happens to the respiratory rate in pregnancy?
It is unchanged
What is the overall effect of pregnancy on the respiratory system?
Why is there physiological hyperventilation in pregnancy?
Increased metabolic production of CO2, so increased respiratory drive from the brainstem to blow off excess CO2
Why is there increased metabolic production of CO2 in pregnancy?
Coming from the fetus, through the placenta, and into maternal circulation
What causes the increased respiratory drive in pregnancy?
What is the result of the increased respiratory drive in pregnancy?
Results in respiratory alkalosis, compensated for by renal bicarbonate excretion
What is the result of the increase in renal bicarbonate secretion in pregnancy?
Decreased buffering capacity, and so increased risk of acidosis, as don't have reserve bicarbonate
Why does physiological dyspnoea occur in pregnancy?
Due to progesterone driven hyperventilation
What happens to O2 consumption in pregnancy?
What happens to resting minute ventilation in pregnancy?
What happens to tidal volume in pregnancy?
What happens to respiratory rate in pregnancy?
What happens to functional residual capacity in pregnancy?
Decreased in T3
What happens to vital capacity in pregnancy?
What happens to FEV1 in pregnancy?
What happens to PaO2 in pregnancy?
What happens to PaCO2 in pregnancy?
What molecules are affected by metabolic changes in pregnancy?
- Thyroid hormones
How does placental transport of glucose occur?
By facilitated diffusion
What happens, regarding insulin, in pregnancy?
Pregnancy increases maternal peripheral insulin resistance
What is the result of the increase in materal peripheral insulin resistance in pregnancy?
Switches to gluconeogenesis and alternative fuels
How is an increase in maternal peripheral insulin resistance achieved?
Human placental lactogen, with contributions from prolactin, oestrogen/progesterone, and cortisol
What happens to blood glucose in pregnancy?
There is a decrease in fasting blood glucose, and an increased in post-prandial blood glucose
What is gestational diabetes?
Carbohydrate intolerance first recognised in pregnancy, and not persisting after delivery
What are the risks associated with poor control of gestational diabetes?
- Macrosomic fetus
- Increased risk of congenital defects
What is a macrosomic fetus?
Larger than average, 4kg at delivery
What is the problem with a macrosomic fetus?
May have problems at delivery, and increased risk of C-section
What is required when gestational diabetes is suspected?
Oral glucose tolerance test
What happens to lipid metabolism in pregnancy?
Increase in lipolysis from T2, and increase in plasma free fatty acids on fasting
What is the increase in lipolysis in pregnancy under the influence of?
Progesterone, from maternal fat stores
Why is there an increase in plasma free fatty acids on fasting in pregnancy?
Ensures mothers physiology has enough FAs for her metabolism, as only essential fatty acids cross the placental membrane and so leaves glucose, the ideal substrate, for fetal metabolism
What happens regarding thyroid hormones in pregnancy?
Thyroid binding globulin production increases, and T3 and T4 increases
What happens to levels of free T4 in pregnancy?
It is in the normal range, due to increase in TBG
What has a direct effect on thyroid stimulating hormone production in pregnancy?
Is TSH ever decreased in normal pregnancies?
Yes, it can be
What are the anatomical changes to the GI system in pregnancy?
Alterations in the disposition of the viscera, e.g. appendix moves to RUQ as uterus enlarges
What is the significance of the movement of the appendix in pregnancy?
Can make appendicitis presentation atypical
Still have umbilical pain
What are the physiological changes to the GI system in pregnancy?
Smooth muscle relaxation by progesterone, leading to;
- Delayed GI emptying
- Biliary tract stasis
- Increased risk of pancreatitis
What can delayed GI emptying lead to?
Why can pregnancy cause biliary tract stasis?
Some biochemical changes in bile salts can increase the risk of gallstone formation
Why is there an increased risk of pancreatitis in pregnancy?
- Can be related to stones
- Can be consequence of hyperlipiaemia of pregnancy
What is immunological true of the fetus?
What is meant by the fetus being an allograft?
It is genetically distinct to the mother, and so will express different HLA molecules to the mother, so is effectively the same as a transplanted organ
What happens to the mothers immuner response as a result of the fetus being an allograft?
Get non-specific suppression of the local immune response at the materno-fetal interface
What is the result of the non-specific supression of the local immune response in pregnancy?
Infection more common in pregnancy
When may the transfer of antibodies between mother and fetus be damaging?
If the maternal circulation has destructive antibodies
What can the transfer of destructive antibodies to the fetus cause in pregnancy?
- Haemolytic disease
- Graves diease
- Hashimoto's thyroiditis
What happens in fetal Graves disease?
Antibodies stimulate the thyroid, so gives the fetus thyrotoxicosis
What happens in fetal Hashimotos?
Destroys the thyroid, so gives hypothyroidism
Is pregnancy a pro- or anti-thrombotic state?
Why is pregnancy a pro-thrombotic state?
It is preparting for partuition and significant blood loss
What prepares for partuition and significant blood loss?
- Substantial fibrin deposition at implantation site
- Increased fibrinogen and clotting factors
- Reduced fibrinolysis
What is the result of the pro-thrombotic state in pregnancy, coupled with stasis and venodilation?
Increases risk of thromboembolic disease
What is the problem with treating thromboembolic disease in pregnancy?
Warfarin crosses the placenta, and is teratogenic
Why can pregnancy cause anaemia?