The first Monday in September may be officially designated as Labor Day, but let’s be honest—every single day is labor day in hospitals across the country, as thousands of women labor to perpetuate the human race. And that form of labor takes plenty of work, as the female body transforms itself from a mere mortal into a miraculous maternity machine.
So as the rest of the country pauses to celebrate the American workforce, we’d like to take a moment to celebrate the astounding female anatomy with a graphic breakdown of how, exactly, women bring new life into the world. The TL;DR version? Women are freaking superheroes.
In order to squeeze something the size of a watermelon through something the size of a lemon, a woman’s body must strrrretch from the inside out—which, like a comic-book hero, it manages to do thanks to a hurricane of hormones.
Starting near the end of a woman’s second trimester, the body releases a hormone called relaxin, which causes the joints in her pelvis to literally relax, explains Dr. Stephanie Romero, an OBGYN and assistant professor at the University of South Florida. The body also releases the hormone progesterone during pregnancy, which (among many things) loosens a woman’s ligaments and muscles. This looseness helps the bones in the pelvis expand during labor, and thus accommodate the baby’s head as it works its way down the birth canal.
Once active labor begins, a woman doesn’t have to worry about pesky feelings like hunger or fatigue—the hormone hurricane suspends these functions until after bébé comes.
Progesterone suppresses the desire for food, Romero says, forcing the digestive system to essentially shut itself down while a woman is laboring. “Your digestive system goes crazy,” she explains. “People get very worried … about not eating while they’re in labor, but you just don’t get hungry. You don’t get hungry and you don’t want to eat.”
Meanwhile, a group of hormones called catecholamines trigger the “fight or flight” response, which essentially makes women preternaturally alert. “Fight or flight keep you awake and gives you the power to keep pushing,” says Romero. “No matter what time of day someone is in labor—whether it’s 1:00 AM or 1:00 PM—they are wide awake and in the moment. There’s not a lot of nodding off during labor.”
In the midst of all this, the brain is releasing the hormone oxytocin, which zooms toward the uterus and fuels contractions, explains Dr. Jeff Livingston, an OBGYN in Irving, Texas. Some women may experience contractions weeks or days before giving birth, while other women only experience contractions for a few hours before delivery.
During early labor, women release a lot of mucus. “Some people say they’ve lost their ‘mucus plug,’” says Romero, “But in reality, there is no one real ‘plug.’ It’s just lots and lots of mucus in the cervix that gets discharged and discharged and discharged. It looks like you blew your nose out of your vagina.”
If that isn’t a rad party trick, I don’t know what is.
Now we’re really rolling. At some point before active labor begins, a woman’s cervix—the opening of the uterus at the back of the vagina—starts to dilate. Once it’s dilated to about four or five centimeters, contractions become more intense and painful, which causes the cervix to dilate faster. When the cervix is about 10 centimeters, a woman is ready to start pushing.
From here, the almighty uterus wows with its strength and power. “The uterus is one big, giant muscle,” says Livingston. “With each contraction, the uterus is squeezing down and contracting and that pressure guides the baby towards the birth canal.”
The uterus is “the force behind everything,” says Romero. “It squeezes the baby and the baby has nowhere to go but out. Then the baby’s head pushes against the cervix, forcing it to disintegrate and open.”
Once the cervix is complete dilated, it vanishes. “It’s not even there anymore,” says Romero. “There’s no other body part that does this disappearing and reappearing act like the cervix does during labor and delivery.”
Indeed, the cervix eventually bounces back into its original shape after labor. “The most amazing part of this whole process is that an opening that normally is so small you have to pull the skin apart to see it becomes relaxed enough to accommodate a human child coming through,” she says, “and then afterwards, it goes back to its old shape.”
Similarly remarkable, as the baby makes its way down the birth canal, its head pushes through a woman’s pelvic muscles without breaking anything, instead causing a gentle spread designed to ensure that nothing gets damaged.
Let’s not forget the vagina, which shape shifts as well during labor.
“Think about putting on a turtleneck sweater,” says Romero. “The neck of the turtleneck is small, but it can stretch. When you push your head through the hole, it expands—and when the head is through, it goes right back to the shape it was before. The vagina is the same way.”
While many women worry that the pressure and process of pushing during contractions will cause them to poop on the delivery table, a reaction on the opposite end of the body is more likely.
“A lot of women vomit,” Romero says. “And people don’t expect that. You’re very likely to vomit when a baby is born. I've even had women who—other than pushing—what made the baby come out of their bodies was the pressure from the act of vomiting.”
The baby has arrived, yay! But the uterus doesn’t call it quits just yet. The organ continues to rapidly contract after delivery, explains Livingston, delivering the placenta and stopping the bleeding that would otherwise jeopardize a woman’s life.
Delivering the placenta “can be as painful as delivering a baby,” says Dr. Shannon Clark, an OBGYN and associate professor at the University of Texas's Medical Branch at Galveston. “Most women feel a big contraction when the placenta comes out.” With the placenta, she explains, also comes a good bit of blood—something that often surprises many women.
“There’s a big gush of blood that goes along with the placenta being delivered, and that scares women a little bit,” she notes. “But as physicians, we’re programmed to know what’s a normal amount of blood and what looks different and needs extra attention.”
From there, the act of breastfeeding—often performed almost immediately after a child is born—triggers the release of more oxytocin, helping the uterus continue to contract and shrink back down to its pre-pregnancy size.
Women who have cesarean sections, in which their babies are delivered surgically as opposed to vaginally, perform superhuman feats as well.
As Romero explains, “You can draw a straight line from the bellybutton to the vulva. And there, you can literally make a hole in the abdominals and stretch them wide enough for a baby to come through—and then they come back together and heal on their own, allowing you to function normally.”
Most incredible of all, according to Livingston, is that “there is no one experience that is the right way or the perfect way for someone to experience labor and delivery. It’s all part of the beautiful way that humans are designed.”
Jen Gerson Uffalussy is a regular contributor to Fusion. She also writes about reproductive and sexual health/policy for Glamour, and television for The Guardian. She lives in Atlanta.