Fetal Circulation

Question 1

Changes in maternal blood volume

Answer 1

Maternal blood volume can increase by 45% per term (more for twins and triplets). Results from increase in plasma volume and erythrocyte volume. Needed to meet the demands of enlarged pregnant uterus and protect against blood loss during delivery

Question 2

Changes in Blood Pressure During Pregnancy

Answer 2

Systemic arterial pressure falls during the first trimester. The decrease in blood pressure results as fall in systemic vascular resistance caused by hormonal activity (progesterone and estradiol) and increased heat production by the developing fetus

Question 3

Functions of the Placenta

Answer 3

Gas exchange, nutrition, waste removal, fluid electrolyte balance, waste removal

Question 4

Placenta Shunt

Answer 4

Shunts blood away via the umbilical arteries from lower limbs and lowers the effective blood flow to abdominal viscera

Question 5

Ductus Venous Shunt

Answer 5

Allows blood via the umbilical vein (55%) to bypass the liver which is largely nonfunctional

Question 6

Foramen Ovale Shunt

Answer 6

Oval hole in the septum dividing the atria, allowing 27% of the blood that comes into the right atrium to enter the left atrium

Question 7

Ductus Arteriosus Shunt

Answer 7

Directs blood from the pulmonary artery to the aorta. Only 7% of the combined cardia output perfuses the unventilated fetal lungs (high pulmonary vasculature resistance)

Question 8

What causes the closure of ductus arteriosus?

Answer 8

Neonatal lungs provide oxygenated blood to the left atrium and increased oxygen tension may be the signal for closure

Question 9

Causes of hypoxaemia

Answer 9

pulmonary vascular resistance and pressure remains high, patent ductus arteriosus which maintains a right to left shunt

Question 10

Cryptogenic Stroke

Answer 10

A stroke that occurs in the absence of an identifies cardioembolic or large vessel source and with a distribution that is not consistent with small vessel disease

Question 11

Persistent Pulmonary Hypertension

Answer 11

result of abnormally high pulmonary vascular resistance/ There is a continuation of right to left shunting of blood through fetal circulatory pathways. Results in hypoxemia.

Question 12

Clinical Features of Persistent Pulmonary Hypertension

Answer 12

Cyanosis, respiratory distress. Loud, single second heart sound or harsh systolic murmur.