Since this is a disease that occurs only in women, is it possible that the unique setting of the placenta in someone who has upright posture might be important. The uterus is not preferentially perfused. In fact, bloodflow to the uterus is very subject to reduction with exercise, large meals, etc. Also, because of posture, when it gets big enough it pushes on the blood vessels and it interferes with its own blood supply and as posture changes that blood supply will come back again. One of the great ways to bring about the formation of free radicals is to have a hyperperfusion/reperfusion setting in which you reduce blood supply and come back again. In things like myocardial infarction, that reperfusion part of it causes a lot of damage.