DEAR DR. MONA: My daughter, who is 24 weeks pregnant, is starting to have swollen legs. I know this happens late in pregnancy sometimes, but her legs look quite big and I am worried about this. Please advise. — Mary Ann

DEAR MARY ANN: As you mentioned, swelling in pregnancy is quite common, occurring in 75 percent of pregnancies. Let me talk a little more about it. The swelling occurs because the body makes more fluids during pregnancy (almost double the blood volume by 26 weeks).

This fluid places pressure on the veins and the blood vessels. In addition, the weight of the uterus containing the baby increases. This extra weight exerts pressure on the large blood vessels in the pelvis and prevents blood flowing from the legs and the lower extremities from going back to the heart. This all results in fluids remaining in the legs and ankles, thus causing swelling. This all takes place over time and does not happen overnight. I am assuming your daughter is dealing with this — a typical pregnancy complaint.

There is swelling that is cause for immediate regular attention, however. If there is sudden swelling in one leg or arm, it is important to see the doctor immediately since this could be a blood clot. During pregnancy there is an increased tendency of the blood to clot and this sudden swelling would warrant immediate intervention to assure that it is not a clot that might progress to the lung and cause pulmonary embolism.

Pregnant women could also suffer from sudden swelling which could accompany a condition known as preeclampsia. This is a more common, but a serious medical condition that requires intervention. The swelling may be accompanied by headache, visual changes and changes in liver function and blood pressure and sometimes can lead to seizures. If this is suspected, an immediate visit is needed to ensure safety of the mother and the baby.

With preeclampsia occurring after 37 weeks of pregnancy, if the symptoms are not controlled, the treatment is delivery of the baby. At an earlier gestational age, the condition and development of the fetus usually dictates the decision. To deliver or not will depend on many factors that are individual and must be discussed with the physician.

So, with the common swelling problems that your daughter seems to be having, here are some relief methods. Keeping the legs up while sitting helps as well as avoiding lengthy periods of sitting or standing. If she is at work and must stand or sit continually, walking around can help. She should never sit with her legs crossed, as this interferes with the blood flow, making the swelling worse.

She should sleep on her left side with legs slightly elevated; this will shift the weight of the uterus off the vena cava and help the blood return from the lower extremities.

Exercise works well. Walking, swimming and other forms of mild exercise, done for about 30 minutes three or four times per week, not only increases the blood flow, but helps to keep the weight down and retain fitness. Swimming is especially good as the weight of the water pressing against the body can help reduce the swelling.

Foods that are high in sodium may make the swelling worse, and caffeinated beverages, such as coffee and tea, can dehydrate the body which will then try to compensate by retaining more water. Although it sounds counterintuitive, drinking plenty of water will help to reduce the swelling.

So I hope this answer to your very good questions is helpful.

Dr. Mona Alqulali is a board certified OB-GYN.