I had pre-eclampsia with my last child, due to my weight and eating habits. To control your weight exercise/walk a lot. You're gonna gain more weight this time so you have to be prepared for it.
Other than that there are medications to control it. I was on Toporol for about 4 months before DS#3 was born and for another 6 months after.
My doctor said that when you are carrying extra weight it's more likely that subsequent pregnancies will result in PE or even Eclampsia. I was 300 pounds which sounds bad but I didn't look that heavy cause I'm a giant.
Since you are already pregnant just eat a great variety of foods with very limited salt. Skip Pasta and rice mixes, make everything fresh and remember to exercise, exercise, exercise.