Edema is swelling caused by excess fluid trapped in the body’s tissues. This abnormal accumulation of fluid in the interstitium, located beneath the skin and in the cavities of the body, can cause severe pain. Clinically, edema manifests as swelling. The amount of interstitial fluid is determined by the balance of fluid homeostasis; and the increased secretion of fluid into the interstitium, or the impaired removal of the fluid, can cause the condition.

Edema in pregnancy is caused by the natural increase in body fluid volume triggered by the hormones estrogen and progesterone and the increased tissue mass applying pressure to the vena cava, which returns blood to the heart from the limbs. Because of this growing pressure the blood flow slows down, leading to the swelling of the feet and legs.

Doctors generally categorize edema during pregnancy as either pitting or non-pitting.

Pitting edema: Characterized by a small indentation left by a little pressure applied on the swollen area (see picture).

Non-pitting edema: The common form of swelling where no dimple or indentation can be seen when pressure is applied.

By James Heilman, MD – Own work, CC BY-SA 3.0