Physiological Adaptations To Pregnancy Flashcards
What urinary changes occur in pregnancy?
Renal plasma flow increases
Increase in GFR by 55%
Functional renal reserve decreases as GFR increases
Urinary stasis due to progesterone relaxing smooth muscle in jreters
What can urinary stasis lead to?
Hydroureter
UTIs
Pyelonephritis - which can induce pre-term labour
What respiratory changes occur in pregnancy?
Diaphragm displaced A-P and transverse diameters of the thorax increase Oxygen consumption increases by 20% Decreased functional residual capacity Increased tidal volume Increase alveolar ventilation rate
What drives physiological hyperventilation and why?
Progesterone
So mother can blow off extra carbon dioxide produced by the fetus
What does physiological hyperventilation lead to and how is this fixed?
Respiratory alkalosis
Kidneys produce less bicarbonate
How does glucose metabolism change in pregnancy?
Altered to favour supply to the fetus
Progesterone diverts glucose into fat synthesis
Oestrogen increases prolactin release which generates maternal resistance to insulin
-maternal glucose usage decreases
-gluconeogensis increases, maximising availability of glucose to the fetus
What other metabolic changes happen in pregnancy?
Amino acid metabolism altered to favour the fetus
Fat laid down in first half of pregnancy to meet demands later on
How are the mother’s energy needs met later on in pregnancy?
Metabolise peripheral fatty acids
How do the glucose concentrations change during pregnancy?
Decrease in fasting blood glucose - hypoglycaemic
Increase in post-meal glucose
What are the risks associated with poor control of gestational diabetes?
Macrosomic fetus
Still birth
Congenital defects
How does gestational diabetes arise?
Rate of insulin secretion needs to increase
This is achieved by β-cell hyperplasia and hypertrophy and increased rate of insulin synthesis in cells
In some, endocrine pancreas cannot increase production so get diabetes due to increased blood glucose
How does lipid metabolism change in pregnancy?
Increase in lipolysis from trimester 2
Increase in plasma concentration of free fatty acids on fasting to provide substrate for maternal metabolism
What does the increased use of free fatty acids increase the risk of?
Ketoacidosis
Combined with respiratory alkalosis, can be very bad
What changes with the thyroid?
Thyroid binding globulin production increases
T3 and T4 increases from hCG
Free T4 in normal range due to increased binding globulin
TSH can be decreased as a result of negative feedback
What anatomical changes happen in the GI tract?
Alterations in position of viscera
-eg appendix moves from RLQ to LUQ
What physiological changes happen in the GI tract during pregnancy?
Smooth muscle relaxation causing
- delayed emptying
- stasis in biliary tree
- increased risk of pancreatitis
Why are pregnant women in a pro-thrombotic state?
High amount of fibrin deposition at the site of implantation
Increased fibrinogen and clotting factors
Reduced fibrinolysis
What can stasis and venodilation lead to?
Thromboembolic disease
Why can’t you give warfarin to a pregnant lady?
Teratogenic
How does anaemia happen in pregnancy?
Plasma volume increases
Red blood cell mass increases but not to same extent
Get physiological anaemia due to a mismatch in volume and haematocrit
Can also be due to an iron and folate deficiency
What does it mean that the fetus is an allograft?
Genetically different to the mother
What happens to the immune system at the materno-fetal interface?
Get non-specific suppression
How can Grave’s disease or Hashimoto’s thyroiditis occur in the fetus?
Antibodies cross the placenta and either
- stimulate TSH receptors
- destroy the developing fetal thyroid
What antenatal screening is done?
Risk factors such as gestational diabetes in history or exam
Blood test for blood group, haemoglobin, infection
Urine analysis for proteinuria
What happens in pre-eclampsia?
Normally, the vessels are vasodilated and plasma is expanded, BP not raised
In pre-eclampsia - vessels are vasoconstricted, plasma contracted, raised BP, proteinuria, pitting oedema
Defect in placentation
Have a poor uteroplacental circulation due to issue with the spiral arteries and widespread endothelial dysfunction
What CVS changes occur in pregnancy?
Blood volume increases
Cardiac output increases by increase in stroke volume
Hypotension
-progesterone
-aortocaval compression by gravid uterus reducing return to the heart
How does GFR change in pregnancy?
Increases by 55%
What happens to the creatinine content in the plasma during pregnancy?
It decreases due to enhanced kidney function
