Pregnancy can change your feet forever. Here’s the science behind 'mom feet.'
Gait changes. Fallen arches. A whole new shoe size. Many women experience these transformations during pregnancy, but the phenomenon is rarely discussed outside the mom group text.
In 2022, American track and field legend Allyson Felix announced that her running shoe brand Saysh would institute an unusual return policy. It stated that if you had purchased a pair of sneakers and your feet changed size due to pregnancy, you could get a new pair.
The policy was a remarkable public acknowledgement of an issue rarely discussed outside the mom group text: pregnancy can permanently alter the size of your feet—making them up to one or two sizes bigger, a phenomenon known as “mom feet.”
And that’s not the only way pregnancy can change your feet. Many women also experience extreme swelling, gait changes, fallen arches, and more. Although these conditions have often been dismissed in the past, some scientists say they should be taken more seriously.
(Scientists are finally studying women’s bodies. This is what we’re learning.)
“Pregnancy is also treated as a temporary condition, so some doctors just kick the can down the road and say once you deliver, things will go back to normal,” says Neil Segal, an associate professor of orthopedics and rehabilitation at the University of Iowa. But as research like his has shown, that just isn’t the case for many women.
Here’s what scientists are learning about how pregnancy changes your feet—and how to deal with it.
Swelling
Swelling of the lower extremities is a very common side effect of an otherwise healthy pregnancy, particularly in the third trimester. As your body starts making more blood to support a baby, the volume of fluids in the body increase while your growing uterus also puts additional pressure on blood vessels in the legs.
“Gravity wins here, with fluid retention typically heading south towards the feet and ankles,” says Dan Geller, a foot and ankle surgeon and chief medical officer for Kane Footwear. The calf becomes what Geller dubs the second heart of the body, helping valves in the veins pump blood back up. When fluid escapes those vessels it can cause pitting edema—or the dimple you may see if you press on the skin with your fingertip.
Although swollen feet are common during pregnancy, they can also be a symptom of something dangerous like blood clots or infections, says Jasmine Pedroso, national gynecology lead at the fertility clinic Kindbody. She adds that you should consult a doctor if your swelling is very asymmetric, very red, warm, and tender to the touch.
Changes to your gait and fallen arches
As your center of gravity changes during pregnancy, it can also change the way that you walk.
We typically walk with pressure shifting from the heel up through to the ball of the foot. But as your belly button creeps further away from your core, the spine becomes less stable, and you feel like you might tip forward.
“That tends to make pregnant women shift their walking pattern to the ball of their foot and everything falls forward,” says Milica McDowell, an orthopedic physical therapist and VP at Gait Happens, an education company focused on improving foot health and gait mechanics. She compares the imbalance to carrying a backpack in front versus on your back where the body is designed to bear more.
(Pregnancy transforms the brain—and some changes last forever.)
Pregnancy can also change the way your feet hit the ground in other ways. The typical weight gain of 25 to 35 pounds dramatically increases the load down through the arch. Geller says the combination of that extra weight and the hormone relaxin that surges through the body during pregnancy can cause the arches to elongate, widen, and fall.
“When we add additional load and all that load being on the front, it’s tough for the arch to recoil back into its elevated position so it starts to flatten,” says McDowell. This ultimately shifts pressure of each footstep from the ball of the foot to the edges instead.
One study published in 2020 found that women with multiple pregnancies were more likely to experience greater overpronation, says Howard Hillstrom, senior director at New York’s Hospital for Special Surgery and co-author of the study.
Plantar fasciitis and bunions
Plantar fasciitis, or fasciopathy, is another regular occurrence during pregnancy, explains Rina Harris a London-based functional podiatrist. This injury to the plantar fascia, the ligament-like structure which runs along the bottom of the feet, is caused by increased laxity in connective tissues, weak foot muscles, tight calves, and extra pregnancy weight. If treated it will fully resolve, says Harris, but if not it can linger and get worse over time.
Meanwhile bunions, an orthopedic deformity at the big toe joint, often result from wearing shoes that are too tight and narrow combined with the increased laxity in your joints caused by the rush of hormones during pregnancy.
(Why do we have bunions? Blame an evolutionary toe failure.)
“Though it usually takes longer than 10 months for bunions to develop, pregnancy can increase their progression,” adds Harris. “Depending on the severity, treatment can help improve alignment, but the big toe joint will never fully restore or regain its original alignment.”
Bigger shoe sizes
Then there’s the shift in foot size that has come to be known as mom feet. Most women who experience mom feet will go up a half size, though some report one or two sizes. Although many will return to their normal shoe size after pregnancy, for others this change can be permanent.
Studies thus far have suggested that fallen arches are the culprit for permanent sizing up, but some researchers suspect that the sensitivity of an individual’s hormone receptors could play a significant role too.
(Just one pregnancy can add months to your biological age.)
While all women experience an increase in hormone levels during pregnancy, only about 40 percent of them are significantly affected by an increased foot length and dramatic drop of the arch, says Segal. “There could be differences in hormone receptors that account for that,” he says, adding however that research around this area is sorely lacking.
Is there anything we can do about it?
Preventative measures can go a long way toward avoiding mom foot and the slew of other foot issues. Pedroso recommends periodic elevation of the lower extremities above your heart, above-the-knee compression stockings, regular stretching and massaging of the lower extremities, frequent light exercise, and a healthy diet that is low in salt.
Shoes are also critical. Harris steers all her patients to shoes that are comfortable and that mimic the shape of the foot—so no pointy toes. “They provide more space for the toes to splay and accommodate any swelling in the feet and ankles, plus they stimulate foot muscles gradually increasing their strength and resilience,” says Harris.
Shoes should also be the right size. According to one 2018 study, between 63 and 72 percent of people are wearing the wrong size shoe. “If they squeeze your toes together, they’re not the right shoe,” says McDowell, who recommends that everyone get their feet professionally measured once a year. And consider your shoe’s structure too. “Supporting the arch throughout pregnancy is very important,” adds Segal.
Although there still hasn’t been enough scientific research devoted to uncovering all the reasons why feet change so dramatically during and after pregnancy, Segal and other researchers argue that they should be taken more seriously. “These are real issues not theories or old wives’ tales,” Geller says.
