15 - Maternal Physiology

Question 1

In general, what are the physiological adaptations that occur in pregnancy?

Answer 1

Question 2

When are hCG at their highest?

Answer 2

• Highest 8-12 weeks then fall as placenta takes over steroid production from corpus luteum

Question 3

What are the immunological changes that occur in pregnancy?

Answer 3

• Mother is immunocompromised so doesn’t attack fetus
• Conditions like psoriasis can improve whilst pregnant

Question 4

What are some respiratory changes that occur in a pregnant woman?

Answer 4

• Needs to increase CO₂ clearance and O₂ delivery

- Increase resp rate a little

- Tidal volume increased which can feel like dypsonea

• Increased respiratory effort and reduction in pCO₂ is due to progesterone sensistising chemoreceptors to CO₂

Question 5

Why do most pregnant women feel dysponea?

Answer 5

Progesterone induced hyperventilation and low pCO_{<em><strong>2</strong></em>,} also need to think about pathological factors like PE, asthma, pneumonia, anaemia, pulmonary oedema

Question 6

What are some of the cardiovascular changes in a pregnant woman?

Answer 6

• Increased SV and HR
• Increased blood flow to breasts, kidney’s and GI
• Decreased SVR as progesterone causes vasodilation of vessels

Question 7

How does a pregnant woman increase their SV and why may they be hypotensive even though they have more volume?

Answer 7

• Hypotensive as progesterone causes vasodilation and decreased SVR
• Cardiac output goes from 4.5L to 6L

Question 8

What are some potential consequences of changes to the cardiovascular system in a pregnant woman?

Answer 8

• Peripheral oedema
• Dilution anaemia (can also be due to folate and iron deficiency)
• Flow murmur
• Upward displacement of apex beat
• Hypotension (usually returns to normal by 3rd trimester)

Question 9

Why are pregnant women in a hypercoagulable state?

Answer 9

• Decreased fibrinolysis
• Increased clotting factors and fibrinogen
• Decreased anticoagulants
• Compression of vena cava

Can’t take warfarin as tetatrogenic so at risk of DVTs, PEs, haemorrhoids, varices

Question 10

What are some changes to renal function that occur in pregnancy and what consequences can they cause?

Answer 10

• Increased RBF so increased GFR by 160%
• Increased RAAS compensate for expected sodium loss
• Serum levels of urea and creatinine fall

Question 11

What are some GI changes that occur in pregnancy, and what consequences can they cause?

Answer 11

• Progesterone causes smooth muscle relaxation to slow emptying so more absorption of nutrients

Heart burn, constipation, gall stones

Question 12

How may the presentation of appendicitis in a pregnant woman be different to the classical presentation?

Answer 12

Uterus may displace the bowel upwards so pain higher up

Question 13

What are some changes to thyroid function in pregnancy?

Answer 13

Vital for fetal development so fetus takes the mothers levothyroxine so mother has to produce more TSH to make more T3/T4

Question 14

What changes to calcium metabolism during pregnancy?

Answer 14

• PTH levels rise
• Placenta makes more hydroxylase so more calcitriol to increase mother’s Ca absorbption so more Ca for fetal bone growth

Question 15

What are some changes to glucose metabolism in a pregnant woman?

Answer 15

• Reduction in maternal blood glucose and aa’s
• Diminished maternal responsiveness to insulin in second half of pregnancy
• Increased insulin release after normal meal
• Increase in maternal free fatty acid, ketone and TAG levels as an alternative fuel

Question 16

How do changes in glucose metabolism occur, in terms of the hormones involved?

Answer 16

- hPL (a.ka hPS): generates maternal resistance to insulin. prolactin does this too

- Oestrogen: stimulates prolactin release

- Progesterone: increases appetite and diverts glucose into fat synthesis

Question 17

How are mother’s energy needs met in pregnancy?

Answer 17

• Glucose used declines as insulin resistance
• Gluconeogenesis and peripheral fatty acids supply mother with energy so fetus can have glucose

Question 18

What is gestational diabetes mellitus?

Answer 18

• Glucose intolerance first recognised in pregnancy and does not persist after delivery.
• Risk of developing Type II DM later in life.
• Diagnosed with OGTT
• Resistance to insulin not met with compensatory rise in insulin so mum is hyperglycaemic

Question 19

What are the risks with gestational DM?

Answer 19

• Macrosomic baby as more insulin in baby that acts like growth factor
• Congenital defects
• Still birth

Question 20

What are some changes that occur to the musculoskeletal system in pregnancy?

Answer 20

Question 21

What are some skin changes that occur in pregnancy?

Answer 21

Increased MSH

Question 22

What is preeclampsia?

Answer 22

Condition relating to placental insufficiency where there is hypertension and proteinuria

• Impaired invasion of trophoblast leads to shallow invasion of spiral arteries so high resistance. Hypoperfusion and ischemia

Question 23

What are some risk factors of pre-eclampsia?

Answer 23

Question 24

What are some of the complications of pre-eclampsia?

Answer 24

Question 25

What are some of the signs and symptoms of pre-eclampsia?

Answer 25

Question 26

What is eclampsia?

Answer 26

• Patient with pre-eclampsia starts to have seizures in pregnancy and multi-organ complications
• 20 weeks gestation to up to 6 weeks after delivery

Question 27

How do we treat pre-eclampsia?

Answer 27

• Stabilise BP
• Monitor baby
• MgSO₄ for seizure prevention
• Fluid restrict and monitor output

Question 28

What are the symptoms of anaemia in pregnancy and why may anaemia occur?

Answer 28

Low folate and iron or dilutional as increased plasma volume

Question 29

What happens to maternal respiratory rate and blood pressure in pregnancy?

Answer 29

• Both stay the same