Why do your legs get so heavy?
One out of every two women are affected by heavy legs syndrome. This is no surprise, given that hormonal variations--from puberty to inappropriate oral contraceptives to menopause--are largely responsible. Still, this weary, heavy, and sometimes very painful feeling occurs most frequently during pregnancy.
It’s mechanical: The purpose of the veins is to bring blood back to the heart. In the legs, this venous return depends on blood pressure (activated by muscle contractions) and the tone of the veins’ walls, along which are placed valves that are supposed to prevent the blood from flowing back down. When these valves are weakened for various reasons, instead of flowing back up, the blood pools and causes a feeling of heaviness: this is heavy legs syndrome, one of the first signs of venous insufficiency.
It’s closely related to pregnancy: Starting in the first trimester of pregnancy, the influx of progesterone reduces tone in the walls of the veins, while estrogens promote edemas. Over the months, the increased volume of the uterus places increased pressure on the main vein responsible for returning blood to the heart. And at the end of pregnancy, when blood pressure is 2 or 3 times higher, the veins distend and the valves are pushed open, no longer preventing this return flow. All of these factors make pregnancy a period particularly prone to heavy legs.