The physical changes a body undergoes during pregnancy are extensive, and one of the less expected alterations is a change in foot size. The size of the feet can increase both temporarily and, for some, permanently. Complete prevention is generally not possible because the changes are rooted in physiological and mechanical processes inherent to pregnancy. Understanding the distinct causes of foot expansion, however, allows for effective management and mitigation of discomfort.
The Biological and Mechanical Causes of Foot Expansion
The primary biological driver for changes in foot structure is the surge of the hormone relaxin, produced to prepare the body for childbirth. Relaxin increases the elasticity of ligaments and connective tissues throughout the body. This softening affects the ligaments that hold the complex bone structure of the feet together, causing them to loosen.
This hormonal laxity means the foot’s intricate arch structure becomes less rigid and more susceptible to collapse. Increased body weight further compounds this effect, pushing down on the loosened arches. As the arch flattens (a process called pronation), the foot’s length and width naturally increase.
The shifting center of gravity caused by the growing abdomen also alters gait and posture, placing new strains on the lower limbs. This redistribution of mass pushes the arch downward and forward, leading to an increase in foot dimensions. The combination of hormonal softening and mechanical overload drives the structural change in the foot.
Distinguishing Between Temporary Swelling and Structural Change
Foot size increase during pregnancy results from two phenomena: temporary fluid retention and lasting structural alteration. Fluid retention, known as edema, is common, especially in the third trimester, and contributes to the puffy appearance and tightness in shoes. This swelling occurs because the body produces more blood and fluid, and the growing uterus puts pressure on major veins, slowing blood return from the lower extremities.
Edema is temporary, and the increased foot volume typically resolves within a few weeks after delivery as the body sheds excess fluid. In contrast, structural change is rooted in the flattening of the arch and the spreading of the foot bones due to ligament laxity and weight. This arch collapse can result in a permanent increase in foot length and width.
Studies show that for a significant percentage of women, foot length increases by a few millimeters, translating to a half or full shoe size increase that does not reverse postpartum. This permanent change is most pronounced after the first pregnancy. While fluid swelling vanishes, the effect of the relaxed ligaments and the flattened arch may remain, requiring a change in shoe size for long-term comfort.
Practical Strategies for Reducing Discomfort
While preventing structural changes is largely impossible, managing swelling and supporting the compromised foot structure can significantly reduce discomfort. One effective strategy for managing edema is to improve circulation. This can be achieved by elevating the feet above the level of the heart for 15 to 20 minutes several times a day to encourage fluid return.
Avoiding long periods of standing or sitting is helpful, as is sleeping on the left side, which takes pressure off the inferior vena cava. Wearing graduated compression socks or stockings can combat fluid pooling by applying pressure to the legs and encouraging the movement of excess fluid back into circulation. These garments also help prevent the formation of new varicose veins.
Footwear selection is paramount for comfort and support. Choose shoes with good arch support, low heels, and a wide toe box to accommodate the foot’s new shape and prevent strain. It is often necessary to purchase shoes a half size or a full size larger or wider than the pre-pregnancy size. Gentle activities like walking or performing simple ankle exercises can also promote blood flow and reduce fluid buildup.