Physiology changes in pregnancy

Question 1

What are the changes in the cardiovascular system in pregnancy?

Answer 1

The SV goes up 30%
The CO goes up 40%
The HR goes up 15%
Diastolic BP decreases in first and second semester but goes to non pregnant levels by term 
systolic BP remains the same

Question 2

What can an enlarged uterus cause in regards to cardiovascular system?

Answer 2

enlarged uterus may interfere with venous return which can lead to ankle oedema, supine hypotension and varicose veins

Question 3

what are the respiratory changes in pregnancy?

Answer 3

Pulmonary ventilation up by 40%, tidal volume from 500 - 700ml (due to effect of progesterone on respiratory centre)
Oxygen requirements increase by only 20%, therefore over breathing leads to a fall in pCO2 - this can give rise to a sense of dyspnoea that may be accentuated by elevation of the diaphragm
BMR up 15% - this may be due to increased thyroxine and adrenocortical hormones - women may hence find warm conditions uncomfortable

Question 4

What happens to components of the blood in pregnancy?

Answer 4

Plasma increase by 50%
Hb falls
red cells increase by 20%
Low grade increase in coagulant activity
rise in fibrinogen and Factors VII, VIII, X
fibrinolytic activity is decreased - returns to normal after delivery (placental suppression?)
prepares the mother for placental delivery
leads to increased risk of thromboembolism
Platelet count falls
WCC & ESR rise

Question 5

What occurs to the urinary system during pregnancy?

Answer 5

blood flow increase by 30%
GFR increases by 30-60%
Salt and water reabsorption is increased by elevated sex steroid levels
Urinary protein losses increase

Question 6

What are the biochemical changes in pregnancy?

Answer 6

Calcium requirements increase during pregnancy
especially during 3rd trimester + continues into lactation
calcium is transported actively across the placenta
serum levels of calcium and phosphate actually fall (with fall in protein)
ionised levels of calcium remain stable
Gut absorption of calcium increases substantially - due to increased 1,25 dihydroxy vitamin D

Question 7

What are the liver changes in pregnancy?

Answer 7

ALP rises by 50%
Albumin levels fall
Hepatic blood flow doesn’t change

Question 8

What happens to the uterus in pregnancy?

Answer 8

100g → 1100g
hyperplasia → hypertrophy later
increase in cervical ectropion & discharge
Braxton-Hicks: non-painful ‘practice contractions’ late in pregnancy (>30 wks)
retroversion may lead to retention (12-16 wks), usually self corrects

Question 9

If a pregnant woman is short of breath, what would you be concerned about?

Answer 9

Acute pulmonary oedema is the fourth most common cause of maternal morbidity and a frequent cause of ITU admission during pregnancy. Peripheral oedema is caused by increased fluid pressure both from sodium and water retention and venous stasis from pelvic obstruction, whereas pulmonary oedema is caused by a change in hydrostatic pressure, either from the heart or from reduced osmotic pressure. These are associated with more sinister underlying conditions, such as sepsis, cardiac disease and from iatrogenic sources. If pulmonary oedema presents with hypertension the diagnosis is likely to be pre-eclampsia, an obstetric emergency.

Question 10

What would be normal signs seen in a cardiac examination of a pregnant women?

Answer 10

The increased cardiac output and volume increase which occur normally during pregnancy lead to the above signs; an ejection systolic murmur is heard in 96% of women and 84% have a third heart sound. Forceful apex beat is not a cause for concern provided it is still within 2cm of the mid-clavicular line