Pregnancy may increase a woman's foot size, a change that appears to be permanent, according to a new study.
Researchers measured the arch height and foot length of 49 women
during their pregnancy and five months after they had given birth. On
average, the women's arch height decreased, and in turn, their foot
length increased between 2 and 10 millimeters (about 0.1 to 0.4 inches) —
during this period.
Overall, about 60 to 70 percent of the women had longer feet and shorter arches after childbirth, the researchers said. Eleven of the women reported changes in their shoe size, the researchers said.
While previous studies have documented changes in foot size during
pregnancy, none had looked to see if the changes persisted after
delivery. "I heard so many women talking about having to go buy new
shoes after pregnancy," said study researcher Neil Segal, an associate
professor of orthopaedics and rehabilitation at the University of Iowa.
This prompted Segal to look into the issue further.
In an earlier study, Segal surveyed about 110 women at a mall, and
asked if their shoe size had ever changed during their adult years.
While just 13 percent of women who'd never been pregnant said it had,
between 30 to 60 percent of women who had been pregnant at least once
said their shoe size had changed.
The change in foot size may be due to the extra weight women carry
around during pregnancy, which puts greater stress on the feet, and,
thus, may flatten the arch, the researchers said. In addition, pregnant
women produce hormones that increase the looseness of the joints and
ligaments (tissue that connects bone to bone), possibly making the foot
structure more malleable.
Most of the women involved in the new study who experienced changes
in their foot length and arch height were first-time mothers. Women had
given birth to two or three children did not experience such significant
changes. This result suggests that a woman's first pregnancy may have
the greatest impact on foot size, the researchers said. But a larger
study will be needed to confirm this, Segal added. (Twenty-nine of the
women in the study were first-time moms; 17 were second-time moms, and
three were third-time moms.)
Changes in the feet during pregnancy may explain why women are at increased risk for pain or arthritis in
their feet, knees, hips and spine than men, Segal said. A flattened
foot can strain the ligaments in the foot's sole, causing changes in
gait that put extra strain on the knees, Segal said.
Segal plans to do more studies to determine if foot changes during pregnancy do
indeed lead to other health problems, such as arthritis. He also plans
to investigate whether modifying the footwear of pregnant women can
prevent foot flattening..
The study will be published in the March issue of the American Journal of Physical Medicine & Rehabilitation.