Baby shunts and oxygen supply

[blazinfury]

If you had a fetus in the womb still attached to the placenta, is there a higher oxygen level within the left atria compared to the aorta? I think that the oxygen level would be greater in the left atria because as blood travels through the body oxygen is constantly being lost. Since the lungs are not patent as of yet, the blood supply that was originally oxygenated at the placenta will lose its oxygen content unless this blood is reoxygenated by the lungs, but since the lungs don't exist it's less.

 

As a side question, lets say we were asked the above question but with the fetus being born (ie lungs working), then I would think that the oxygen concentration in blood in aorta would be slightly larger.