Edema, or the minor swelling of the extremities, is considered normal during pregnancy. Increased retention of fluids, hormonal changes, and the growth of the uterus all combine to puff up a woman's legs and feet, and much more slightly her arms and legs. The swelling is worst during the third trimester of pregnancy, as her body gears up for labor and the fetus grows considerably in size.
Several factors can increase a woman's edema during pregnancy. Prolonged exposure to heat and humidity cause the blood vessels to swell, so she should try to avoid long hours in the sun. Gravity works all too well, so she should also avoid standing for extended periods of time and might try propping her feet up or reclining. The uterus is already placing undue pressure on her veins, causing blood to pool in her legs and feet, so it is important that she alternate between standing and sitting throughout the day. In the same vein, she might find some relief by sleeping on her left side at night.
Edema can also be influenced by diet--particularly sodium, potassium, and caffeine levels. Increasing her intake of water can also help relieve some of the swelling. She should wearing loose-fitting clothing, avoid stressful or strenuous situations, and participate in regular, mild exercise.
While cankles may not be the most attractive thing in the world, the swelling should completely disappear within a few days of giving birth. And unless the swelling is rapid, extreme, or spreads to her face, it's also probably not cause for concern. Consider this a happy excuse to pamper yourself; float in a pool, recline in a chair, or take a pleasant walk.