Physiological Adaptations To Pregnancy

Question 1

What urinary changes occur in pregnancy?

Answer 1

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

Question 2

What can urinary stasis lead to?

Answer 2

Hydroureter
UTIs
Pyelonephritis - which can induce pre-term labour

Question 3

What respiratory changes occur in pregnancy?

Answer 3

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

Question 4

What drives physiological hyperventilation and why?

Answer 4

Progesterone

So mother can blow off extra carbon dioxide produced by the fetus

Question 5

What does physiological hyperventilation lead to and how is this fixed?

Answer 5

Respiratory alkalosis

Kidneys produce less bicarbonate

Question 6

How does glucose metabolism change in pregnancy?

Answer 6

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

Question 7

What other metabolic changes happen in pregnancy?

Answer 7

Amino acid metabolism altered to favour the fetus

Fat laid down in first half of pregnancy to meet demands later on

Question 8

How are the mother’s energy needs met later on in pregnancy?

Answer 8

Metabolise peripheral fatty acids

Question 9

How do the glucose concentrations change during pregnancy?

Answer 9

Decrease in fasting blood glucose - hypoglycaemic

Increase in post-meal glucose

Question 10

What are the risks associated with poor control of gestational diabetes?

Answer 10

Macrosomic fetus
Still birth
Congenital defects

Question 11

How does gestational diabetes arise?

Answer 11

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

Question 12

How does lipid metabolism change in pregnancy?

Answer 12

Increase in lipolysis from trimester 2

Increase in plasma concentration of free fatty acids on fasting to provide substrate for maternal metabolism

Question 13

What does the increased use of free fatty acids increase the risk of?

Answer 13

Ketoacidosis

Combined with respiratory alkalosis, can be very bad

Question 14

What changes with the thyroid?

Answer 14

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

Question 15

What anatomical changes happen in the GI tract?

Answer 15

Alterations in position of viscera

-eg appendix moves from RLQ to LUQ

Question 16

What physiological changes happen in the GI tract during pregnancy?

Answer 16

Smooth muscle relaxation causing

• delayed emptying
• stasis in biliary tree
• increased risk of pancreatitis

Question 17

Why are pregnant women in a pro-thrombotic state?

Answer 17

High amount of fibrin deposition at the site of implantation
Increased fibrinogen and clotting factors
Reduced fibrinolysis

Question 18

What can stasis and venodilation lead to?

Answer 18

Thromboembolic disease

Question 19

Why can’t you give warfarin to a pregnant lady?

Answer 19

Teratogenic

Question 20

How does anaemia happen in pregnancy?

Answer 20

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

Question 21

What does it mean that the fetus is an allograft?

Answer 21

Genetically different to the mother

Question 22

What happens to the immune system at the materno-fetal interface?

Answer 22

Get non-specific suppression

Question 23

How can Grave’s disease or Hashimoto’s thyroiditis occur in the fetus?

Answer 23

Antibodies cross the placenta and either

• stimulate TSH receptors
• destroy the developing fetal thyroid

Question 24

What antenatal screening is done?

Answer 24

Risk factors such as gestational diabetes in history or exam
Blood test for blood group, haemoglobin, infection
Urine analysis for proteinuria

Question 25

What happens in pre-eclampsia?

Answer 25

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

Question 26

What CVS changes occur in pregnancy?

Answer 26

Blood volume increases
Cardiac output increases by increase in stroke volume
Hypotension
-progesterone
-aortocaval compression by gravid uterus reducing return to the heart

Question 27

How does GFR change in pregnancy?

Answer 27

Increases by 55%

Question 28

What happens to the creatinine content in the plasma during pregnancy?

Answer 28

It decreases due to enhanced kidney function