Physiology in Pregnancy

Question 1

What are the general changes we see in a persons physiology during pregnancy ?

Answer 1

• Mechanical
• Metabolism (become anabolic then becomes catabolic to make sure glucose and energy goes to foetus and get insulin resistance, insulin production increases almost 2 food if no diabetes before)
• Fatigue (particularly early pregnancy)
• Heartburn/Reflex (Hormones makes everything looser)
• Oedema (70-80% get due to changes in serum osmotic pressure, if unilateral = DVT)
• Breasts (Montgomery tubercles form and self cleaning?)
• Thyroid (thyroid binding globulin increases, T3+4 is same but works harder. Graves is more common and can cause hyperthyroidism in foetus. Remember don’t treat with carbimazole as teratogenic, treat with Propylthiouracil!)
• General state of immunosuppression (important in allowing baby to implant)
• Weight gain

Question 2

What 3 things suggest Pre-eclampsia?

Answer 2

• High BP
• Proteinuria
• Oedema

Question 3

What changes occur in the Cardiovascular system?

Answer 3

Significant changes occur early in first trimester;
- Increase blood circulating volume of 50-70%
- Systemic vascular resistance falls - maximal at weeks 20-32
- Increased blood flow
- Increased cardiac output (40%), stroke volume and heart rate increases (SVxHR = CO)
- Increased O2 consumption

Get 25% reduction in cardiac output when on back as compressing IVC (never do CPR on lying down woman).

Main cause off maternal fatality is due to CVS (Especially if congenital underlying). Can get mitral stenosis or dilated cardiomyoopathies with increase in preload. Get changes in ECG with axis deviation, inverted t waves, ejection systolic murmur.

Everything goes back to normal 6-8 weeks after birth

Question 4

What trends should we see in BP and why is this important?

Answer 4

BP drops a little towards middle pregnancy and rises a little towards end, some women who go on to develop pre-eclampsia their BP doesn’t drop in end 2nd semester.

Question 5

What 3 Intrapartum CVS changes do we see?

Answer 5

• Autotransfusions of contractions
• Pain - increasing catecholamines (also increase HR and BP). Can give epidural in those with heart disease to reduce work of heart, can have complications though).
• CO increases by 10% in labour and by 80% in 1st post delivery hour (All blood in uteroplacental unit goes back into blood, vital time for women with heart conditions and can become fluid overloaded). Every labour contraction pushes 500ml of blood back into bloodstream

Question 6

What 6 Postpartum CVS changes do we see?

Answer 6

• Return to normal by 3 months (usually)
• Blood volume decreases by 10% 3 days post delivery
• BP initially falls then increases again 3-7 days (pre pregnancy by 6 weeks)
• SVR increase over first 2 weeks to 30% above delivery levels
• HR returns to pre pregnancy over 2 weeks
• CO increases by up to 80% 1st hour post delivery then continues to fall over the next 24 weeks

Question 7

What 9 respiratory changes do we see in pregnancy?

Answer 7

• Significant increase in O2 demand (20%)
• 40-50% increase in minute ventilation
• Increased respiratory rate
• Increased tidal volume
• Decreased functional residual capacity
• PEFR and FEV1 unchanged
• PCO2 decreases
• Acid base balance
• O2Hg dissociation curve

Everything works harder and baby needs O2 and CO2 out, Diaphragm moves up to work harder.

Acid base changes due to ventilation, so different in pregnancy, CO2 is lower and Po2 a bit higher (slightly alkalotic) so mother can compensate for baby

Question 8

What 10 changes do you see in the Renal System during pregnancy?

Answer 8

• Dramatic dilation of urinary collecting system - more pronounced on right
• Increased renal plasma flow - 60-80% by end of second trimester
• GFR and creatinine clearance increases by up to 50%
• Protein excretion increased (which reduces serum osmotic pressure)
• Microscopic haematuria may be present (can be dilation of ureters)
• 80% women develop oedema
• Glycosuria common (kidneys spill out glucose)
• Rate increases as gestation increases
• Urea and creatinine decrease
• UTI’s are more common

eGFR and AKI aren’t accurate in pregnancy, eGFR raises dramatically means getting rid of waste better.

Hydronephrosis more prone in right kidney than left.

Can often get ketones in fasting blood samples because pregnant women in short periods of starvation will break down triglycerides for baby.

More prone to UTI’s, urethra shortens and cannot empty bladder as well

Question 9

What 8 haematological changes will you see during pregnancy?

Answer 9

• Plasma volume increases cf birthweight
• Haemoglobin, Haematicrit and Red Cell Count decrrease
• No change to MCV or MCHC
• Decrease platelet count
• 2-3 fold incase in requirement for iron
• 10 - 20 fold increase in folate requirements
• WCC increases
• Hypercoagulable

Hypercoagulable - less likely for blood loss during pregnancy but DVT and PE increased. VTE is the leading cause, many pregnant women die from PE each year

If carrying twins more likely to be anaemic as babies take your iron

ITP Immune thrombocytopenia (ITP) is a type of platelet disorder. In ITP, your blood does not clot as it should, because you have a low platelet count.

Also congenital thrombocytopenia

Recommend increase in folic acid as it reduce risk of conditions like spina bifida

Question 10

How do lab values change during pregnancy?

Answer 10

Super increased;
- Alkaline phosphate (placenta produces a lot!)

Increased;
- WCC
- ESR
- 24 hour protein
- D dimer (due to increased coagulation)

No change;
- Platelets (or slightly down)
- CRP
- AST/ALT/GGT (or slightly down)

Decreases;
- Hg (20.5 instead of 11.5 is normal)
- Urea
- Creatinine
- Urate (but increases with gestation)
- Total Protein
- Albumin (excrete more protein and become oedematous)