What causes edema during pregnancy?

Edema during pregnancy is primarily caused by increased blood volume and hormonal changes. As pregnancy progresses, a woman's body undergoes numerous physiological adaptations to support the developing fetus. One significant change is the expansion of blood volume, which can increase by as much as 50% to meet the demands of both the mother and the growing placenta.

Additionally, hormonal changes, particularly the elevated levels of progesterone and relaxin, contribute to the relaxation of blood vessels and an increase in vascular permeability. This means that fluid can more easily seep into the surrounding tissues, leading to swelling.

While other factors such as physical activity levels, fluid intake, and weight gain may influence the presence and severity of edema, they are not the primary underlying causes. For example, excessive weight gain can contribute to edema, but it is not a direct cause in the way that changes in blood volume and hormones are. Similarly, insufficient fluid intake might lead to dehydration but is not a direct contributor to the swelling experienced in pregnancy. Increased physical activity typically helps promote circulation, which can help reduce edema rather than contribute to it. Thus, the interplay of increased blood volume and hormonal changes is central to understanding why edema occurs during pregnancy.