A common side effect of pregnancy is many women undergo as much as one shoe size in growth of their feet. According to a recent research from the University of Iowa first-time mothers saw the most significant changes in their foot size. Associate professor, Dr. Neil Segal conducted the study by measuring women’s feet at the beginning of their pregnancy and five months after delivery. Forty nine (49) women took part and between 60 to 70 percent saw their feet get wider and longer (by between 2mm and 10mm) as a result of the pregnancy. First-time mothers saw the most significant changes to their shoe size, but any subsequent pregnancies may or may not continue to change their size and shape of the foot. In previous studies changes to foot morphology have been explained by increased body mass combined with the presence of the hormone “relaxin” which facilitates the birth process by causing a lengthening and softening of the cervix and the pubic symphysis. Relaxin also works on the ligaments in the feet and may case the foot arch to flatten. Segal believes changes in foot morphology during pregnancy contribute to why women are disproportionately at risk of osteoarthrosis of weightbearing joints. Reference
Segal N, Boyer, Elizabeth R, Teran-Yengle, Patricia P, Glass, N. A, Hillstrom H, and Yack, H. J. (2013) Pregnancy Leads to Lasting Changes in Foot Structure" American Journal of Physical Medicine & Rehabilitation March 2013 - Volume 92 - Issue 3 - p 232–240.