It is common for feet to increase in size during pregnancy, often requiring new, larger shoes. This physical change is a well-documented consequence of the biological shifts that occur in the body to support fetal development and prepare for childbirth. Understanding the specific mechanisms behind this foot expansion helps clarify which changes are temporary and which may be permanent.
The Hormonal and Physical Reasons for Foot Expansion
Foot expansion during pregnancy stems from a combination of hormonal, circulatory, and mechanical factors. The primary biological trigger is the increased production of the hormone relaxin, which prepares the body for delivery. Relaxin increases the laxity of ligaments and joints throughout the body, allowing for greater flexibility during birth.
This systemic effect causes the ligaments supporting the arches of the feet to become more pliable and stretched. As these structures loosen, the increased body weight associated with pregnancy applies greater mechanical stress to the feet. This pressure causes the longitudinal arch to flatten, leading to a measurable increase in foot length and width.
The third factor is fluid retention, known as edema, which causes temporary swelling in the extremities. Blood volume increases significantly during pregnancy, and the growing uterus places pressure on the major veins returning blood from the lower body. This fluid accumulation in the feet and ankles contributes to a noticeable, usually reversible, increase in overall foot volume.
The Likelihood of Reversal: Temporary Swelling vs. Permanent Change
Whether feet return to their pre-pregnancy size depends on the underlying cause of the change. Swelling caused by edema is temporary and resolves relatively quickly after delivery. Once the excess fluid and blood volume stabilize, typically within a few weeks postpartum, the temporary increase in foot volume disappears.
However, structural changes involving ligament lengthening and arch flattening can be permanent. The lengthening of the ligaments, caused by relaxin and sustained mechanical load, may not fully reverse. Studies indicate that for a significant number of women, the feet remain permanently longer and wider than they were before pregnancy.
Research following women from early pregnancy to several months postpartum found that between 60% and 70% experienced a lasting increase in foot length and width. This permanent change often translates to needing a shoe that is a half-size to a full-size larger than the pre-pregnancy size. This structural change is attributed to the flattening of the arch, which causes the foot to lengthen by a few millimeters.
The most significant structural changes are often observed after a woman’s first pregnancy, with subsequent pregnancies having a lesser or negligible additional effect. For those who experience this permanent change, the new foot structure is typically stable around five months after childbirth. Therefore, a definitive determination of permanent shoe size should wait until the hormonal and fluid shifts have fully stabilized many months postpartum.
Practical Steps for Comfort and Management
Managing discomfort and size changes during and after pregnancy involves addressing temporary swelling and the need for proper structural support. To reduce edema, it is helpful to elevate the feet above heart level whenever possible throughout the day. Wearing supportive compression stockings that reach above the knee can also assist in maintaining healthy circulation and moving excess fluid out of the lower extremities.
Staying hydrated and engaging in light, regular exercise, such as walking, can improve circulation and reduce fluid retention. When sleeping, lying on the left side can help remove pressure from the inferior vena cava, which is the large vein that returns blood to the heart, thus improving blood flow and reducing swelling.
Choosing the correct footwear is important to minimize arch collapse and maintain comfort. Shoes should have a low heel, a wide toe box, and adequate arch support to accommodate swelling and prevent further flattening of the arch. Avoid shoes with tight straps or restrictive bands that could pinch or impede circulation. If a woman notices a sudden, severe, or asymmetrical increase in swelling, or if the swelling is accompanied by other symptoms like a severe headache, she should consult a healthcare professional immediately, as this could indicate a more serious condition.