So the final fact that that facilitates the diffusion of oxygen across our placenta is something called the double bore effect. So let's recall what a bore effect is. So, the bore effect is basically the ability of carbon dioxide to affect the affinity of hemoglobin. So the more carbon dioxide we have in the blood, the less likely that hemoglobin will actually bind onto that oxygen. And conversely, the less CO2 we have in the blood, the more likely our oxygen, our hemoglobin, will actually bind to oxygen. So what exactly do we mean by double bore effect?