Fetal Circulation

Question 1

Describe the fetal circulation.

Answer 1

Oxygenated - Umbilical vein - IVC, FO, LA, LVC Aorta

Deoxygenated - SVC and IVC flows through RA, RV, PA, DA, Descending aorta

Question 2

What is streaming?

Answer 2

Directs oxygenated blood at FO

Question 3

Why are the feta lungs different antenatally?

Answer 3

Fluid filled and collapsed therefore very high resistance

Question 4

What does the ductus arteriosus do?

Answer 4

Blood from PA -> Aorta

Question 5

Relationship BP vs GA

Answer 5

Positive

Question 6

RV pressure vs GA. LV vs RV? Atrial pressures?

Answer 6

Positive.

Equal pressures.

Atrial pressures of 0 - 4 mmHg, no change related to GA

Question 7

How much blood goes to the lungs in the fetus?

Answer 7

17%

Question 8

How is volume flow distributed L v R in fetus?

Answer 8

Slight RV dominance 1.2:1

Question 9

How is the fetal circulation assessed?

Answer 9

Ultrasound

Question 10

What changes at birth?

Answer 10

PVR decreases dramatically.

FO and DA close.

Placenta gone, therefore R heart seeing decreased pressures and L heart seeing increased afterload/resistance

Question 11

What is the effect of increased pulmonary blood flow?

Answer 11

Due to reduced PVR.

Closes FO. Increases LA pressure.

Question 12

Why does the arterial duct close?

Answer 12

Inhibition of PGE synthesis