I had this with Harry too and it was what made the decision for a c section to be done on the day that he was born.
I was told that the blood flow from the placenta was going to the Harry and coming straight back out again, so that the Harry was getting little or no nutrition; oxegen etc. There are apparently 4 grades that this level of blood flow can be at and when it reaches grade 4 as happened with Harry, there really is no option but to take the baby out. About 3 days before Harry was born it was at grade 2, so it moved pretty quickly to grade 4 and I guess we were lucky to get him out when we did. My blood pressure at that stage was not too bad but teh protein in my urine rose quite quickly over that period too and platlets deteriorated.
Hope this helps.
Baby #1 Harry 28/4/03 1lb 10oz, 27 weeks 3days, severe PE and reverse ED flow
Baby #2 due 28/11/05