Swelling during pregnancy is a normal phenomenon as the body undergoes significant changes to support a healthy pregnancy. Fluid accumulation resulting in swelling is referred to as edema and there is a number of reasons why this arises in pregnancy, without the need for any concern. This normal swelling is often evident in the second and third trimester of pregnancy and is more pronounced in the hands and arms, feet and legs as well as the face.
Most frequently, the changing hormone levels cause sodium retention (commonly referred to as salt retention) and this in turn causes the body to retain water. Furthermore the circulating blood volume is increased and the blood vessels as well as tissue spaces have to accommodate this increased fluid content.
However, there are instances where this swelling should not be passed off as normal part of pregnancy. Swelling may be a sign of a more serious underlying disorder that needs prompt medical attention or the health of both mother and child may be at risk.
Causes of Leg, Foot, Ankle Swelling when Pregnant
Trauma and Strain
Injuries should always be excluded as a causes of swelling. Ankle sprains and falls are more likely in late pregnancy as the mother adapts to a larger size and change in center of gravity. Fractures should always be excluded as a possible cause of swelling, especially after a fall. Pain is usually present as a result of trauma.
Any injury resulting in a break in the skin or any insect bites should be taken seriously in a pregnant woman and medical attention should be sought. This is discussed further under cellulitis (below). Certain infections may not result in cellulitis but the microorganisms can cause other diseases which could put the pregnancy at risk.
Swelling isolated to the feet and ankles or affecting the entire leg may also be a result of strain – excessive walking, prolonged standing and sporting activities like jogging. Any swelling that eases during the night but is pronounced during the day without any other signs and symptoms may be an indication of overuse. Pain is usually not present or may be mild and should ease with rest.
This is one of the most common causes of leg swelling in pregnancy. The hormone changes affect the rigidity of the vein walls and valves. The uterus compresses the inferior vena cava and partially obstructs blood flow from the femoral veins. Blood flow back to the heart from the leg veins is therefore affected but this does not usually pose any risk to mother or baby.
Signs and symptoms
- Green, red or purple spider veins (small network of vessels) which are visible through the skin. As the condition progresses, larger portions of the vein become visible.
- Skin rashes or discolored skin (dark pigmentation)
- If there are any leg ulcers evident then this should be investigated further for possible complicating factors like diabetes.
The swelling is often exacerbated when standing for long periods or on hot days. Varicose veins may resolve after childbirth or it can persist. Patients should also be cautious about deep vein thrombosis due to stasis of blood present in varicose veins.
Deep Vein Thrombosis
This is the presence of a blood clot inside a blood vessel of the legs which is known as a thrombus. It usually affects one side only although there may be the risk of both legs (bilateral) being affected simultaneously. In pregnancy, the pressure of the enlarged uterus on the iliac veins slows the flow of blood returning from the legs (venous stasis). For a further explanation of this process, refer to Causes of Thrombosis. Other causes and risk factors may also be present for a deep vein thrombosis which could be unrelated to pregnancy.
Signs and symptoms
- One-sided leg, foot and ankle swelling (unilateral)
- Tenderness of the leg, particularly of the calf
- Reddish skin that is warm to touch
A significant obstruction of the blood flow may result in acute limb ischemia. This is further explained in the article on Blood Clot in the Leg.
Pregnant women who are cigarette smokers (even if it smoking has been discontinued), with a history of varicose veins or peripheral arterial disease, blood clotting disorders or inactive should be cautious about the possibility of DVT.
Cellulitis is an inflammation of the deeper layers of the skin (dermis and hypodermis) due to an infection. Pregnant women with varicose veins and other circulatory disorders should be cautious. Cellulitis is often preceded by a break in the skin, either due to a cut or some other injury including animal scratches or bites and minor abrasions. However, in women who are immunocompromised (impaired immune functioning), cellulitis may occur without any break in the skin.
Signs and symptoms
- One-sided leg swelling
- Itchy, burning or painful skin rash which is warm to the touch
- Tenderness of the leg which is pronounced at the affected site
- Fever (sometimes)
Cellulitis must always be attended to immediately by a medical doctor. There is a risk of the infection spreading to the uterus and resulting in a miscarriage (septic abortion) or sepsis may occur which could be fatal.
This condition is related to high blood pressure (hypertension) and proteinuria (protein in the urine) in pregnancy. It typically affects women after the 20th week of pregnancy. Preeclampsia is a risk to both mother and baby and requires medical attention.
Signs and symptoms
- Bilateral leg swelling (both legs) although edema may sometimes not be present. Swelling may also be evident in the hands and arm. Swelling is often sudden and excessive.
- Hypertension (high blood pressure)
- Proteinuria (urine in the protein)
- Nausea and vomiting
- Shortness of breath
- Blurred vision
- Young mothers (younger than 20 years) and older women (older than 40 years)
- Vascular disorders
- Kidney disease
- Rheumatoid arthritis
- SLE (lupus)
- Multiple pregnancies
- First pregnancy
- Family history of preeclampsia
Any pathology of the joint may result in leg swelling and this is often exacerbated during pregnancy. The additional weight and altered gait due to a change in the center of gravity may place extra strain on the joint. If the joint on one side is affected, the change in gait often puts additional strain on the other leg in an attempt to compensate for the pain. Women with conditions like rheumatoid arthritis may often find that the condition exacerbates during pregnancy. For more information on swelling of the knee and ankle, refer to the article on Swollen Joints.
There are a wide range of causes of leg swelling which should be considered and this is discussed further under the Swollen Leg article.