Swelling occurs when there's more fluid in your body tissues than normal (water retention). Your feet, face and hands will probably swell (edema) and your rings will likely become too tight at some point during the pregnancy. As the due date approaches, swelling often becomes more noticeable.
Fluid pools in your ankles if you're standing for extended periods of time. This is especially prone to happen in hot weather. Another aggravating factor is high blood pressure, which can force fluid from the bloodstream into the tissues. Pregnancy hormones also play a role, causing retention of sodium by the kidneys, which causes the body to retain fluid.