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　　Women might expect to need new clothes after giving birth. But a bigger pair of shoes? Well, yeah. Because pregnancy¹ can actually lengthen² and widen a woman's feet. That’s according to a study in the American Journal of Physical Medicine and Rehabilitation³ that’s probably not a surprise to a lot of women.

　　Neil Segal, a rehab doc at the University of Iowa, heard that some local women had to don larger shoes after pregnancy. So he and colleagues measured the feet of 49 women during their first trimester(三个月) and again five months after childbirth. Indeed, nearly half the women went up a shoe size after childbirth, to accommodate their longer, flatter feet. And multiple pregnancies⁴ may add to that effect, Segal says.

　　Pregnant women produce a hormone⁵ called "relaxin(松驰肽；耻骨松驰激素)," which makes the pelvis(骨盆) more flexible. That's good for childbirth. But the hormone can affect joints⁶ and ligaments(系带；韧带) elsewhere, like in the foot. Adding pregnancy weight to that flexibility⁷ can lead to permanent flattening⁸ of the foot's arch - associated with knee and hip⁹ pain in older women. Segal's now investigating whether custom(定做的) shoe inserts(嵌入物) can protect women against that risk, and help get motherhood off on the right foot.