During pregnancy, pain may often appear elsewhere in the body, says podiatrist Rina Bimbashi. In pregnancy, the impact of the weight gain is compounded by the effect of hormones. "During pregnancy, there is an increase in three hormones — relaxin, oestrogen and progesterone — which soften the muscles and ligaments in preparation for childbirth, making them more flexible," adds Mrs. Bimbashi.
The problem is that if you have mild to moderate degree of overpronation before pregnancy, the looseness of the ligaments means your feet can roll in even more. As a result, you can end up with moderate to severe overpronation (the effects of these hormones are evident in ligaments and muscles for about five months after giving birth). "Pregnancy has a huge impact upon your whole joint alignment, and your muscles and ligaments need to work much harder in order to maintain stability. I commonly see women who have good, normal foot arches which collapse during pregnancy leading to very excessive pronation."
Source: Jenny Hudson, Daily Mail [5/21/12]