L14: maternal physiology

Question 1

Describe glucose metabolism in pregnancy

Answer 1

Fat laid down in the first half of pregnancy helps meet the demands of the fetus later in the pregnancy when the fetus is metabolically most demanding
Changes which occur:
-reduction in maternal blood glucose & amino acid concentrations
-diminished maternal responsiveness to insulin in second half of pregnancy
-increase in maternal free fatty acid, ketone & triglyceride levels
-increased insulin release in response to a normal meal

Question 2

Describe hormones which influence maternal glucose metabolism during pregnancy

Answer 2

1) Human placental lactogen – generates a maternal resistance to insulin (prolactin also has a similar role)
2) Oestrogen – stimulates an increase in prolactin release
3) Progesterone – increase appetite in the first half of pregnancy, and diverts glucose into fat synthesis

Question 3

Describe gestational diabetes

Answer 3

Glucose intolerance that is first recognised in pregnancy and does not persist after delivery
Leads to maternal hyperglycaemia
Associated with increased birth weight, congenital defects & stillbirth

Question 4

Describe cardiovascular changes that occur in the mother during pregnancy

Answer 4

Fetal-placental’s increasing need for nutrition is met via maternal vascular-neogenesis
Accommodated by changes in function of maternal baro- and volume receptors
Plasma volume increases & cardiac output increases to 6L/min -> achieved mainly through increase in stroke volume as compared to heart rate
Therefore, flow murmurs & upward displacement of the apex beat can occur
Increased progesterone -> vasodilation -> hypotension

Question 5

Describe pre-eclampsia

Answer 5

Condition relating to placental insufficiency, which manifests itself as a clinical syndrome in pregnancy of hypertension and proteinuria
Important to control this condition -> can lead to intrauterine growth restriction, preterm labour & infant respiratory distress syndrome
In mother, pre-eclampsia can progress to eclampsia = characterised by seizures & other multi-organ complications

Question 6

Describe haematological changes that occur in the mother during pregnancy

Answer 6

Pro-thrombotic state – increased clotting factors & fibrinogen, decreased fibrinolysis
Can lead to thromboembolic disease, but can’t treat with warfarin = teratogen
Increased blood volume, but RBC mass does not increase to same extent -> physiological anaemia

Question 7

Describe respiratory changes that occur in the mother during pregnancy

Answer 7

Tidal volume and oxygen uptake increase appreciably
Increased awareness of the desire to breathe is common – may be interpreted as dyspnoea
-increase in tidal volume -> lowers the pCO2
-increased respiratory effort & reduction in pCO2 induced by progesterone acting directly on respiratory centre -> sensitising chemoreceptors to CO2 changes

Question 8

Describe renal changes that occur in the mother during pregnancy

Answer 8

Increased blood flow causes an increase in GFR to 160% of normal
Creatinine clearance increases, and serum levels of urea and creatinine fall

Question 9

Describe gastrointestinal changes that occur in the mother during pregnancy

Answer 9

Progesterone causes smooth muscle relaxation throughout the GI tract -> causes slow gastric emptying
Can cause nausea, constipation and heartburn
Gallbladder emptying is also reduced

Question 10

Describe calcium metabolism during pregnancy

Answer 10

Placenta also contributes the maternal synthesis of calcitriol
Aims to increase maternal calcium absorption which leads to greater calcium availability for the fetus -> allow optimal bone development

Question 11

What are the complications of pre-eclampsia for the fetus?

Answer 11

Pre-eclampsia leads to poor uteroplacental perfusion
-reduced kidney perfusion: reduced production of amniotic fluid
Fetal growth restriction