I was induced at 39 weeks with baby no 3. Not because of pre-eclampsia though.
Pessory went in at 7pm, nothing happened until 9.30 the next morning when contractions started but were not regular or strong. They broke my waters at 6pm, baby arrived 1hr 40 later. Normal delivery, no intervention or stitches.
It can be a long slow frustrating process, but can equally be extremely quick. It's impossible to say how it's going to go, just be prepared for a long 2 day ordeal and anything sooner is a bonus!! I found the worse thing was people messaging constantly....only tell the people you really need to the day you are going in!!!!! Good luck, it's worth it!