Foot growth is a common physical change many women experience during pregnancy, often resulting in shoes feeling tight. This phenomenon is not due to the bones actually growing, but rather a combination of hormonal shifts and physical strain causing the foot structure to spread and temporarily increase in volume. Understanding the biological and mechanical reasons behind this change provides insight into managing foot health.
The Role of Hormones in Softening Ligaments
The primary biological mechanism behind structural foot changes is the increased production of the hormone Relaxin. This hormone’s main function is to prepare the body for childbirth by softening and relaxing ligaments and connective tissues throughout the body. While most noticeable in the pelvis to widen the birth canal, its systemic action affects the feet as well.
Relaxin makes the ligaments supporting the arch of the foot, such as the plantar fascia, more pliable. When these supporting structures lose tension, the arch can flatten and collapse under body weight. This laxity allows the bones of the foot to spread slightly, increasing both foot length and width.
Increased Weight and Fluid Retention
Hormonal effects are compounded by two significant physical changes during gestation: increased body mass and fluid retention. The natural weight gain associated with pregnancy places greater mechanical pressure on the already softened ligaments. As the arch flattens under this increased weight, the foot elongates and widens, a process known as overpronation.
Fluid retention (edema) also contributes to a temporary increase in foot size. During pregnancy, blood volume expands, and pressure from the growing uterus impedes the return of fluid from the lower extremities. This accumulation causes noticeable swelling, adding to the foot’s overall girth and volume. The key distinction is that weight-induced arch collapse causes a structural change, while edema causes temporary, volume-based swelling.
Are the Changes Permanent?
Whether foot size changes are permanent depends on the underlying cause. Swelling caused by fluid retention is temporary and typically subsides within the first few weeks after delivery, returning the foot volume to its pre-pregnancy state. However, the structural changes resulting from Relaxin and increased mechanical pressure are often lasting.
When the arch collapses, the foot’s structural integrity is altered, resulting in a permanent loss of arch height and an increase in foot length. Studies indicate that for a significant percentage of women, the feet become permanently longer, with an average increase ranging from 2 to 10 millimeters. This elongation often translates to needing a half to one full shoe size larger than before pregnancy. The most significant and lasting structural changes tend to occur during a woman’s first pregnancy.
Supporting Foot Health During Pregnancy
To manage discomfort and minimize structural changes, women should adopt supportive measures for their feet. Choosing appropriate footwear is effective, prioritizing shoes with excellent arch support and a wide toe box to accommodate spreading. Supportive inserts or orthotics can also help stabilize the foot and reduce strain on lax ligaments.
Managing Edema
To combat temporary swelling from edema, several steps promote fluid drainage and circulation:
- Elevating the feet above the waist throughout the day to promote fluid drainage.
- Wearing compression socks to aid circulation and reduce fluid accumulation.
- Avoiding standing for long periods.
- Engaging in gentle exercises, such as walking, to promote healthy blood flow and alleviate discomfort.