And if we plot this curve on the x y axis, where the x axis is the partial pressure of oxygen given in millimeters of mercury, and the y axis is the percent saturation of that hemoglobin, we get the following curve. So the blue curve is the curve that describes the adult hemoglobin, while the red curve describes the fetal hemoglobin. And notice at the same partial pressure, let's say at 40 degrees partial pressure of oxygen, the adult hemoglobin has much less saturation than the fetal hemoglobin does. And that's because a fetal hemoglobin does not actually bind to two, three BPG. And so it is much more likely to actually attract other oxygen molecules and bind to those oxygen molecules. So we see that the maternal red blood cells have hemoglobin, the adult hemoglobin that binds oxygen much less readily than the fetal red blood cells that contain the fetal hemoglobin.