Hi Michelle
From what I read from when they told me I had low fluid levels with Max (obviously totally different situation) normal is regarded as between 5 and 25cm, they begin to get concerned when they drop below 5cm as bubs has less room to move around and is at risk of sitting on the cord (so to speak) I have also read that low fluid can be related to leaking fluid, pre eclampsia, and diabetes. Obviously you know you have the PE so it's probably related to that.

My understanding is that you will get monitored at least weekly through u/s to check the levels and if they become too low they will deliver.

In the mean time they suggest drinking plenty of water and getting heaps of rest (yeah right I hear ya)

Take care