No, not all swelling has to do with your bp. Sometimes pregnancy just causes some women to swell, particularly if it's warm or you've been on your feet for a while. Not all women swell during pregnancy, so you may never have this happen to you. I tend to swell in my ankles (I'm 37wks), but if I put my feet up and drink water they go back to normal.
I was told that swelling in the face, and swelling to the point of it leaving an indention after you touch it could indicate something more serious where I need to contact my doctor.