Both of them are caused by the placenta
, from what we can tell, and IIRC having one puts you at higher risk of developing the other, probably because it means you've got a weird placenta in there. Though to be fair, *all* placentas are weird.Treating gestational diabetes seems to lower PE risk
The idea is that the placenta is messing around with maternal metabolism, because *that's just what it does*, and it is more likely to be unhappy about how it's implanted and trying to alter the rate at which nutrients are appearing on the upside of the flow if it's predisposed to preeclampsia. A lot of these things are hypoxia-induced triggers; in other words, when the placenta runs short of oxygen because it's smaller than usual or shallowly implanted, these switches start to be thrown.