Well, the mainstream medical can offer meds to lower bp, but that isn't the ideal. There are lots of things you can do with nutrition, supplements, and herbs though to keep you as healthy as possible. of course, it is no guarentee of perfect health, but won't hurt either.
There are great suggestions in the book "Wise Woman Herbal for the Childbearing Year" by Susun Weed.
Last pregnancy, I worked closely with my midwife on nutrition. We talked LOTS about the sorts of things I needed to eat (protein, fruits, veggies) and the things I didn't need to eat (candy, sugar, coffee, caffine in general, etc). I also took lots of baths, rested as needed,and just worked hard to keep my bp low. A pre-e sentence once doesn't mean that you will have to face it again.