Pregnancy is a time of great physical change. The most obvious of these changes is a large increase in weight, centered over the front of the pelvis. This increase in weight can cause pain in the legs, either directly or from its effect on the lower back. A less obvious change of pregnancy is an increased tendency to form blood clots, which is known as a hypercoagulable state. While this hypercoagulable state is not a problem for most women, in some it can cause blood clots in the leg, which is another potential source of leg pain. Pain from these causes is equally likely in either leg.
Muscle and Joint Pain in the Legs
Most women gain at least 20 pounds when pregnant, and some gain as much as 100 pounds. This extra weight increases the load on the joints in the leg, particularly the knee and hip, which can lead to pain. The pain may be felt at the joints themselves, or it may radiate to other areas of the leg. Joint pain is more likely in heavier women, since there is a correspondingly greater load on the joints, according to the book "Williams Obstetrics." In addition, the increased weight means that the muscles in the leg have to work harder during ordinary activities such as standing and walking. This extra work can lead to muscle strain and also cause pain in the legs. Muscle and joint pain during pregnancy is rarely serious and is best treated by rest, heating pads and Tylenol. Never take aspirin, ibuprofen or naproxen when pregnant unless directed to do so by a physician.
Back Pain
In addition to the legs, the extra weight of pregnancy can cause pain in the back. The weight of the baby is extended over the mother's pelvis, which shifts her center of gravity forward, notes "Williams Obstetrics." The muscles in her lower back have to work harder to counteract this shift of balance, which can result in strained muscles, tendons and ligaments. This sort of lower back pain sometimes radiates to the upper legs and is appreciated as originating from that location, according to the book "Harrison's Principles of Internal Medicine." Leg and back pain from this source is rarely serious and is best treated in the same way as muscle and joint pain originating in the legs.
Deep Vein Thrombosis
The most dangerous cause of leg pain during pregnancy is a clot in the deep veins of the leg, called deep vein thrombosis, or DVT. This thrombosis occurs most frequently in the calf, although it can form in the thigh as well, notes "Harrison's Principles." By contrast, pain from muscles and joints in the leg or back is much more likely to be felt in the thigh. Other symptoms of a DVT include mild swelling, color change and increased warmth. While pregnancy is a hypercoagulable state, the increased risk from pregnancy alone is so small that DVTs are extremely rare in pregnant women without other risk factors, according to "Williams Obstetics." The presence of other risk factors, such as smoking, obesity, prolonged immobility and certain inherited disorders that increase blood clotting make DVTs during pregnancy much more likely. A DVT is an urgent condition that requires prompt medical attention but is usually not an emergency. The principle danger from a DVT occurs when part of the clot breaks off and travels to the lungs. This condition is called a pulmonary embolism, and it is a serious medical emergency.
References
- "Williams Obstetrics"; F. Gary Cunningham; 2010
- "Harrison's Principles of Internal Medicine"; Dennis L. Kasper; 2005
