Calcium/magnesium to lower BP?

[HeatherlovesCDs]

My BP is borderline, but I have a history of it going up around 30-32wks in my previous 3 pregnancies. I'm 20wks now. I've heard of taking calcium and magnesium to lower blood pressure, but I've never actually done it or even researched it. My blood pressure seems to be more of a concern this time than it has been in the past. It hasn't dipped down much like it normally does in the 2nd trimester. So...I'm a little nervous.

Anyone know about this protocol for treating it? I'd specifically like to know how much I should take. I'll start researching too, but I'd love to hear first hand experience. Thanks!