Now let's consider something that isn't disease related!

 

There are actually different types of hemoglobin.

 One that is made during adulthood (Hb) and one that you make when you are a fetus developing in the womb (fetal hemoglobin, FHb).

 Take a look at the following images to give you an idea of how oxygen needs to be transferred from the pregnant individual to the developing fetus:

Carefully looking at the placental organ, you might appreciate that the maternal blood supply is separate (but surrounds) the fetal blood vessels (you can trace these from the umbilical cord). That means maternal blood never mixes with fetal blood.

 

Maternal hemoglobin must drop the oxygen, that oxygen crosses cells layers (called syncytiotrophoblasts) and the oxygen is picked up by FHb (fetal hemoglobin).

 

But how does the fetal hemoglobin achieve this "stealing" of maternal oxygen?