I had terrible swelling in my hands and feet when I was pregnant with my daughter. I never heard exact diagnoses of what it was, but it may have been a form of water retention. This is simply an excess of fluid draining into the areas around the cells from the blood.
The water retention remedies work best when they address the exact cause. Again, the SIGN of water retention is fluid coming out of the blood vessels and flooding the surrounding tissues resulting in the obvious swelling of body parts.
The more exact causes of water retention include: excess salt, excess minerals, stress, and not enough exercise.