The researchers found that 60 to 70 per cent of the women in the study saw arch height and measures of arch rigidity decrease significantly from early pregnancy to five months after childbirth, causing corresponding increases in foot length - between 2mm and 10mm - and arch drop.
Professor Neil Segal, of the University of Iowa, said: "I had heard women reporting changes in their shoe size with pregnancy, but found nothing about that in medical journals or textbooks.
"We found that pregnancy does indeed lead to permanent changes in the feet."
The study also suggested that first pregnancies may account for most of the observed changes, while second, third, or higher pregnancies may not further alter foot structure.
"It is possible that these foot changes that occur during pregnancy may help explain why, in comparison with men, women are at higher risk for pain or arthritis in their feet, knees, hips, and spines," Prof Segal said.
- DAILY MAIL