Many pregnant women notice that their feet have grown as their shoes often get tight as early as the second trimester. The feet continue to increase in size and flatten until late in pregnancy. The reason why flat feet are a common problem is because the arch of the foot flattens. This is most likely due to the increased laxity of the joints or due to the extra weight women put on during pregnancy.
Medical textbooks and journals don’t offer too much information about this topic. The University of Iowa study, which was funded by grants from the National Institute on Aging and by the American Geriatrics Society, measured 49 women’s feet at the beginning of their pregnancy and after delivery. Researchers found that in close to 70 percent of the cases women feet become wider and longer. It was also observed that while these changes are permanent they don’t lead to an important change in the distribution of pressure over the two feet. Second or third pregnancies have a relatively small chance of altering the foot structure even more as mainly the changes only occur during the first pregnancy.