84 Effect of pregnancy on maternal physiology

Question 1

Uterus grows to occupy most of the pelvis by __ weeks, palpable abdominally from __ weeks

Answer 1

Uterus grows to occupy most of the pelvis by 16 weeks, palpable abdominally from 13 weeks

Question 2

At term the uterus reaches what level?

Answer 2

Level of the xiphoid process (thorax widens as the ribs flare to accommodate organs)

Question 3

What happens to structures on posterior abdominal wall during pregnancy?

Answer 3

Compressed when lying down

Question 4

Changes to centre of gravity resulting in what during pregnancy?

Answer 4

Development an accentuated lumbar lordosis

=> Backache

Question 5

Result of relaxin release during pregnancy?

Answer 5

Causes softening of ligaments

=> Sacroiliac and pubic symphysis pain

Question 6

Anatomical changes to mother during pregnancy?

Answer 6

• Fist sized organ grows to occupy most of the pelvis by 16 weeks, palpable abdominally from 13 weeks
• At term uterus reaches the level of the xyphoid process (thorax widens as the ribs flare to accommodate organs)
• Compression of structures on the posterior abdominal wall especially when lying down
• Changes centre of gravity develop an accentuated lumbar lordosis. Leads to –> Backache
• Relaxin causes softening of ligaments. Leads to–> Sacroiliac and symphysis pubis pain
• Weight gain averages 12.5kg

Question 7

Cause for 12.5kg weight gain in pregnancy?

Answer 7

• 6kg uterus, foetus and breast
• 3kg fat reserves for lactation
• Remainder is fluid

Question 8

Result for pressure on IVC from foetus?

Answer 8

• Impedes venous return from LLs
• Impairs function of valves
=> Varicose veins

Question 9

Cause for physiological anaemia in pregnancy?

Answer 9

Haematopoiesis is increased up to 30%
BUT
Increase in plasma volume (up to 50%) means that RBC count, haematocrit and haemoglobin conc are all reduced

Question 10

Changes to WBC, platelets count and clotting factors during pregnancy?

Answer 10

• Small increase in WBC
• Unchanged platelet count, but more reactive
• Increase in clotting factors with thromboembolism risk

Question 11

Circulatory adaptations to TPR during pregnancy?

Answer 11

• Uteroplacental circulation is characterised by high volume, low resistance flow
- Due to uterine spiral arteries and arterioles inability to vasoconstrict

• Pregnancy hormones = Reduce sensitivity to pressor agents (e.g. angiotensin) to vasoconstrict. => peripheral vasodilation occurs and TPR reduces

Question 12

Result of peripheral vasodilation in pregnancy women?

Answer 12

Heat intolerance

Question 13

Reduced TPR triggers what?

Answer 13

Triggers the renin-angiotensin-aldosterone system increasing blood volume

Question 14

Effect of oestrogen in maintaining normal (low) blood pressure in foetus?

Answer 14

Vasodilation:

Oestrogen increases vascular endothelial growth factor (VEGF) and NO production in endothelial cells

Question 15

What does VEGF mean?

Answer 15

Vascular endothelial growth factor

Question 16

What do endothelial cell release in order to help maintain the low BP in the foetus?

Answer 16

Prostacyclin (prostaglandin I2 or PGI2)

• vasodilator

Question 17

Changes to CO during weeks 6 -28 of pregnancy?

Answer 17

(CO = HR x SV)
Increases by 30-50%

• Increase in HR to 80-90/min
• Increase SV by ~ 10%

Question 18

Which organs receive increased blood flow during pregnancy?

Answer 18

Uterus, breast and skin

Question 19

Why is CO sensitive to posture during late pregnancy?

Answer 19

• Can fall because of IVC obstruction by uterus

* Resulting in hypotension/fainting when lying flat

Question 20

At which point does the CO return to pre-pregnancy condition postpartum?

Answer 20

By 6 weeks

Question 21

How is BP measured in pregnant women?

Answer 21

Measured semi-recumbent using Korotkoff phase 5 for diastolic

Related to changes in circulating plasma volume and peripheral resistance

Question 22

Changes toBP in second trimester?

Answer 22

BP normally falls in second trimester

• Systolic falls ~5-10mmHg
• Diastolic falls ~10-15mmHg

Question 23

What is pre-eclampsia?

Answer 23

Placental problem involving an increase in BP,

proteinuria and oedema

Question 24

Potential cause for pre-eclampsia?

Answer 24

May involve failure of the 2nd wave of trophoblast invasion that normally impairs the capacity of maternal spiral arterioles to constrict (12-16 weeks)

Question 25

Consequences of pre-eclapsia?

Answer 25

• Poor placental perfusion can cause foetal growth restriction • Increased vascular resistance in placenta causes: – Decreased blood to placenta – Hypertension in mother – Renal arteriolar endothelial damage causes oedema, glomerular damage and proteinuria (‘acute atherosis’)

Question 26

What is eclampsia?

Answer 26

``` Extreme hypertension (e.g. 180/120) • Increased intracranial pressure, seizures, coma • Significant risk of cerebral haemorrhage ```

Question 27

Maternal mortality of eclampsia?

Answer 27

~ 8-36%

Question 28

Interventions to treat eclampsia?

Answer 28

* Magnesium sulphate * Antihypertensives * Rapid delivery * Careful fluid balance

Question 29

Changes to respiratory system in mother during pregnancy?

Answer 29

``` • Progesterone increases sensitivity of central CO2 receptors • More ventilation • Increase in tidal volume by ~ 40% • Ventilation rate unchanged ```

Question 30

Changes to renal system during pregnancy?

Answer 30

* Kidneys deal with foetal urea => increased renal function * Increased glomerular filtration rate (GFR), as a result of increased CO, by ~30-50% * Decreased plasma urea, creatinine and uric acid * Bladder is compressed leading to frequent and urgent urination * Ureters are dilated that can predispose to infection

Question 31

Why is uric acid the most useful renal marker in pregnancy?

Answer 31

It rises before creatinine in response to renal impairment (e.g. pre-eclampsia)

Question 32

Changes to total body water (TBW) during pregnancy?

Answer 32

TBW increases by ~6-8L • Extracellular fluid (ECF) increases by ~3L, split between plasma and interstitial fluid (ISF)

Question 33

Changes to osmolality during pregnancy? Why?

Answer 33

Osmolality falls by ~10 mOsm/kg • Decreased urea and creatinine

Question 34

3 main changes to GI system in pregnant women?

Answer 34

1. Morning sickness, nausea/ vomiting - esp. first 12-14 wks 2. Constipation 3. Gastric acid reflux, heartburn

Question 35

Cause for morning sickness?

Answer 35

* Parallels HCG levels | * Worse in multiple pregnancy & hydatidiform mole

Question 36

Cause of constipation in pregnant women?

Answer 36

* Pressure of uterus on rectum and lower colon | * Decreased motility, progestogenic effect on smooth muscle

Question 37

Cause for gastric acid reflux in pregnant women?

Answer 37

* Relaxation of lower oesophageal sphincter * Relaxation of GI smooth muscle (progestogenic effect) * Pressure of uterus * Worse lying down * Aspiration risk during endotracheal intubation

Question 38

What are the nutritional requirements of a pregnant women?

Answer 38

``` • Weight gain at term is ~7-14kg – Foetus 3.5kg – Placenta and amniotic fluid 1.5kg – Increased breast tissue 0.5-1kg – The rest is fat and extracellular fluid (ECF) ``` * Daily calorific requirement increases by ~15% * 200-300 kcal/day

Question 39

What happens in early pregnancy?

Answer 39

* Rate of growth of foetus relatively slow to 20 weeks * ~3kg fat laid down to provide energy source for final trimester when growth is very rapid * Maternal tissues more sensitive to insulin in early stages of pregnancy * Increased protein synthesis

Question 40

When does growth of foetus peak?

Answer 40

Between 30-36 weeks

Question 41

What happens in later pregnancy?

Answer 41

* Relative insulin resistance, predisposing to ‘high-normal’ glucose levels * Increased lipolysis supplying mother with source of energy * Increase in circulating triglycerides stored in mammary tissue * Increased requirement for protein

Question 42

``` Gestational diabetes: • Spectrum? • Risk factors? • Predictor for? • Associations? ```

Answer 42

• Spectrum from normal to ‘impaired glucose tolerance’ to actual diabetes • Risk factors: – Race – Obesity – Family history • Can be a predictor of future type 2 diabetes • Associated with foetal macrosomia (increased insulin resistance; high glucose) and complications

Question 43

Vitamin requirements of pregnant women?

Answer 43

* Folic acid needed for neural tube fusion (pre-conception) * Vegetarians may need to increase B12 intake * High levels of vit A may lead to foetal abnormalities * Vit D supplementation is recommended

Question 44

Mineral requirements of pregnant women?

Answer 44

Calcium; • Maternal gut absorption increases • Active transport across the placenta • Increase in release from maternal bone

Question 45

Role of zinc in pregnancy?

Answer 45

* Important role in many metabolic processes * Protein synthesis * Nucleic acid synthesis * Synthesis/activity of insulin * Increased dietary need, especially in vegans

Question 46

Role of iron in pregnancy?

Answer 46

* Globally, high incidence of maternal iron deficiency * If dietary iron low, may need supplements * Supplementation with normal iron stores is undesirable, may increase oxidative stress

Question 47

Placenta secretions?

Answer 47

* hCG has key role in maintaining pregnancy | * Other placental proteins and steroids

Question 48

Endocrine secretions from the mother?

Answer 48

* Increased growth hormone release * Decreased FSH and LH * Increased prolactin * Increased parathyroid hormone * Pituitary increases in size (production of prolactin and ACTH and oxytocin) * Thyroid increases in size due to hCG (similar in structure to TSH)

Question 49

Postnatal changes to mother?

Answer 49

• Uterine involution complete by 6 weeks • Amenorrhoea if breast feeding – Duration related to frequency and duration of suckling – May be associated with hot flushes and vaginal dryness • Systemic changes largely reversed by 6 weeks – Coagulation system changes may take longer – Glucose tolerance normalises very rapidly