Well, let's take a look at the following diagram to see what the double bore effect is. So, let's suppose that this purple line is basically our placental membrane. And our gas exchange takes place across the placental membrane, which is basically this coryonic membrane shown right here in purple. So this is the side of the mother. This is the side of the fetus. So what happens is carbon dioxide moves down its concentration gradient from this side from the fetus's side to the mother's side.