Physiology in Pregnancy

Question 1

What are some of the general changes that occur during pregnancy?

Answer 1

• Mechanical changes: Relaxin causes relaxation of the ligaments in the pelvis and softens and widens the cervix
• Reflux: because of relaxation of sphincters
• Fatigue – particularly early pregnancy
• Oedema because in 3rd trimester they are unable to excrete sodium as effectively
• Thyroid: iodine deficiency, if already deficient there will be goitre
• General state of immunosuppresion
• Weight gain - 2kg in 1st tri, 5kg in both 2nd and 3rd trimesters. (12kg is about normal total gain)

Question 2

What are the breast changes in pregnancy?

Answer 2

• Increased size and vascularity – warm tense and tender
• Increased pigmentation of the areola and nipple
• Secondary areola appears
• Montgomery tubercules appear on the areola
• Colostrum like fluid can be expressed from the end of the 3rd month

Question 3

What are some of the CVS changes in pregnancy?

Answer 3

• Significant changes during 1st trimester
• Increased circulating blood volume -50-70% of non pregnant
• Systemic vascular resistance falls – maximal at 20-32 wks
• Increased blood flow
• Increased cardiac output (40%), stroke volume increases (SVxHR= CO)
• Increased heart rate
• In supine position – 25%reduction in cardiac output
• Increased O2 consumption

Question 4

Why if lying flat will you get a 25% reduced in cardiac output?

Answer 4

The IVC is compressed by the enlarged fetus

Question 5

How should CPR change when with a pregnant woman?

Answer 5

Put her in left lateral position – need to use pillows of jumper if you are outwith hospital

Question 6

Why do women appear to have a glow when they are pregnant? What is the role of the epidural and what are the risks?

Answer 6

increased blood flow, for the same reason they are susceptible to nose bleeds (purely physiological).

Pain removal BUT also increases BP but increasing peripheral vasodilation

Question 7

What are the interpartum (during pregnancy) CVS changes?

Answer 7

• Autotransfusion of contractions
• Pain - causing increased catecholamines
• CO increases by 10% in labour and by 80% in 1st post delivery hr

Question 8

What are the postpartum (post pregnancy) changes?

Answer 8

• CVS should return to normal by 3mths
• Blood volume decreases by 10% 3 days post delivery
• BP initially falls then physiological increases again days 3-7(pre preg levels by 6 wks)
• SVR increase over first 2 wks to 30% above delivery levels
• HR returns to pre preg over 2 weeks
• CO increases by up to 80% 1st hr post delivery then continues to fall over the next 24 weeks

Question 9

What are the respiratory changes during pregnancy?

Answer 9

• Significant increase in oxygen demand (20%)
• 40-50% increase in minute ventilation
• Increased respiratory rate
• Increased tidal volume
• Decreased functional residual capacity
• PEFR and FEV1 unchanged
• PCO2 ↓

Asthmatics do not really change during pregnancy – because of endogenous steroids produced

Lungs are squashed in pregnancy

75% women suffer SOB – majority is purely physiological

Question 10

What are the changes in the renal system due to pregnancy?

Answer 10

• R kidney tends to become dilated: because uterus tends to push this way
• Increased renal plasma flow – 60-80% by end of second trimester
• GFR ↑ and creatinine clearance increases by up to 50%
• Protein excretion increased
• 80% have oedema
• More prone to UTIs because of shortening of urethra
• Gestational diabetes (this is screened for)
• Glycosuria common
• Urate ↑ with increasing gestation
• Urea ↓, creatinine ↓

Question 11

What are the haematological changes in pregnancy?

Answer 11

• Physiological anaemia – plasma volume increases and haem cannot catch up, platelets drop because of dilution
• Iron deficiency anaemia – iron goes to fetus, so iron need is 3x
• Folic acid: given to reduce neural tube defects (10-20x increase requirement)
• WCC increases
• Hypercoagulable

Question 12

What happens to Hg, WCC, platelets in pregnancy?

Answer 12

• Hg - decreases
• WCC - increases
• platelets - decrease/stay same

Question 13

What happens to CRP, ESR, Urea, Creatinine, Urate?

Answer 13

• CRP: stays same
• ESR: Increase
• Urea/Creatinine: decreases
• Urate: decreases (but increases with gestation)

Question 14

What happens to 24hr protein, total protein, albumin?

Answer 14

• 24hr protein: increased
• Total protein: decreased
• Albumin: decreased

Question 15

What happens to AST/ALT/GGT, Alk Phos?

Answer 15

• AST/ALT/GGT: decrease/stays the same
• Alk Phos: Increases a lot [placenta produces]

Question 16

What happens to bile acids/d dimer?

Answer 16

• Bile acids: stay the same
• D dimer: increased