They say that being a mother changes you, and they aren't kidding. At no other time in your life will you grow a whole new organ, force your heart to pump 50 percent more blood and have alien cells hijack your brain.
And while most of those odd changes disappear after birth, a few of them, like your little one, are for keeps. From permanently bigger feet to diabetes, here are 18 things that may never go back to the way they were before pregnancy.
There are two main reasons for the change in shoe size during pregnancy: weight gain and hormones.
The American College of Obstetricians and Gynecologists (ACOG) says that women of a normal weight should gain from 25 to 35 lbs. (11 to 16 kilograms) during pregnancy. "That extra weight that's carried around for the 10 lunar months of pregnancy, and even longer, flattens out the [foot's] arch," which is why some women gain about half a shoe size during pregnancy, said Dr. Michael Cackovic, the obstetrics director of cardiac disease and pregnancy at The Ohio State University Wexner Medical Center.
The hormone relaxin also plays a role. As its name suggests, relaxin helps relax ligaments and bones in the pelvis, so the body can be elastic during childbirth. But relaxin also affects ligaments all over the body, including in the feet, which can make a woman's feet looser and more spread out, said Dr. Leena Nathan, an assistant clinical professor of obstetrics and gynecology at the University of California, Los Angeles.
New moms: Once your feet grow, you should get used to sporting a larger shoe size, as these changes are permanent, even after you lose weight and relaxin production stops, Cackovic said.
And speaking of weight gain, while those extra pounds don't have to be permanent, they are for many women.
One in 4 women will hang onto 11 lbs. or more (5 kg or more) a year after giving birth. And after having a baby, a woman will be, on average, 2.5 to 5 lbs. (1 to 2 kg) heavier than she was prior to pregnancy, Kathleen Rasmussen, a professor of maternal and child nutrition at Cornell University, previously told Live Science. While that's not a ton, imagine repeating that process for four or five babies; after that, the extra weight gain can be significant
This one shouldn't be a surprise, given the average dimensions of a newborn's head, but women often have vaginal changes postpartum. While the vagina will contract down to almost its original size after birth, most women will have a permanently wider vagina, said Dr. Alyssa Dweck, a gynecologist in New York City and the author of "The Complete A to Z for Your V," (Fair Winds Press, 2017).
"There are many factors that contribute, including type of delivery, size of baby, genetic factors [and] being overweight, to name a few," Dweck told Live Science.
While not all women face one of the more unpleasant problems associated with squeezing an 8-lb. (3.6 kg) human out of their body, giving birth — unfortunately — puts mothers at increased risk for incontinence, or loss of bladder control. That's because vaginal delivery can weaken the muscles needed for bladder control and can damage bladder nerves and supportive tissue, leading to a dropped (prolapsed) pelvic floor, according to the Mayo Clinic.
C-sections can also increase the risk of incontinence, Cackovic said.
Women with incontinence can practice Kegel exercises to strengthen these pelvic floor muscles, he said. There is also at least one Bluetooth-enabled device that allows people to do pelvic floor exercises and get biofeedback with an app on their phone and a small intravaginal device, Dweck said.
Gain a child, lose a tooth
The old wives' tale says, "Gain a child and lose a tooth." And there may be some truth to that.
A 2008 study of 2,635 women in the American Journal of Public Health found that the more children women had, the more likely they were to have lost teeth. Women between the ages of 35 and 49 with one child had lost an average of two teeth, while women with two children lost an average of four. Meanwhile, women with four or more children had lost an average of seven teeth. It's not clear exactly why, as frequency of dental care didn't seem to be tied to this association.
Other dental problems include enlarged gums and more bleeding from gums during pregnancy because of increased blood flow, Nathan told Live Science. And the acid from vomiting, if women have morning sickness, can also wear away the enamel on teeth, Nathan said.
Hormonal changes during pregnancy can also affect the bacteria population, or microbiome, of your mouth, so it's important to practice good dental hygiene during this time, Cackovic said.
"We know that women who don't have good dental health are actually at risk for preterm delivery, so it's very important for women to see their dentists during pregnancy and get their teeth cleaned according to schedule," Nathan said. "If it's not taken care of, it can definitely persist postpartum."
Growing and shrinking breasts
A woman's breasts go through some big (and little) changes during and after pregnancy.
"They get bigger at first, because the dormant fat tissue in the breast gets replaced by functional tissue" in preparation for breastfeeding, Cackovic said.
But these larger breasts don't last forever. "After a woman stops breastfeeding, that functional tissue atrophies, because it's not being used anymore," Cackovic said. "And then it's not immediately replaced by fat, because the fat is already gone."
If the woman gets pregnant again, then the process will repeat. And if the woman gains a lot of weight after a pregnancy, then she'll replace those fat cells in her breasts. "But generally, if somebody is a very fit person and doesn't gain weight, then [her breasts] are going to stay smaller at that point," Cackovic said.
The technical term for this super-depressing side effect of pregnancy is ptosis. And once breasts droop, they will not perk up again, because the cause of breast drooping is the stretching of the ligaments and elastin that hold the fatty tissue in place, according to 2008 study in the Aesthetic Surgery Journal.
One positive? Once you've had that baby, breastfeeding is unlikely to make breast sagging worse. A 2010 study in the journal Annals of Plastic Surgery found that women who had been pregnant had more sagging than those who had not. But while weight gain, smoking status and additional pregnancies worsened droopiness, breastfeeding did not.
Lower breast-cancer risk
While breasts may be losing their fight against gravity, here's one fact that may perk you up: Breastfeeding may lower the lifetime risk of developing breast cancer. For every 12 months a woman nurses a baby, her relative risk of breast cancer drops by 4 percent, according to a 2002 review in The Lancet.
Crunching the numbers, the authors suggested that up to half of the breast cancer risk in developing countries could be cut if women had as many babies as they did in developing countries, and two-thirds of that risk reduction was due to breastfeeding. (There are, however, other benefits associated with having fewer kids.)
Pregnant women might notice pink or red stretch marks on their skin during pregnancy. Granted, this condition isn't unique to pregnancy; people can get stretch marks any time they experience a big increase or decrease in weight, Cackovic said.
The good news is that while stretch marks stick around, they do get much lighter over time. "They usually do fade out in one to two years," Cackovic said. However, "if the woman gets pregnant again, or gains or loses a lot of weight again, they may become more pronounced."
Women often notice that the hair on their head is lusher and denser during pregnancy. But why does this happen?
The answer has to do with hormones. Increased levels of hormones can translate into fewer hairs lost during pregnancy. That's why women may have a thicker head of hair during pregnancy.
After hormones levels return to normal post-pregnancy, that luscious hair goes away. "It's not uncommon for women to complain at six months that their hair is falling out," Cackovic told Live Science. "But [hair loss] is really just a temporary thing and usually resolves by about 12 to 18 months."