If you've never been through it before — or if you're a man and thus immune — it's hard to imagine what it feels like to be pregnant. But the urge to know is clearly strong. Witness the Mommy Tummy, a Japanese invention released in 2011 that uses balloons and a water pump to simulate pregnancy for men.
The Mommy Tummy takes pregnancy from zero to nine months in a mere two minutes, which may not seem quite fair to women who spend the better part of a year in gestation mode. Perhaps the hosts of the Dutch television show "Guinea Pigs" made a more valiant effort: In January, Dennis Storm and Valerio Zeno hooked themselves up to electrodes to simulate the pain of labor over a two-hour period. In 2009, an Australian TV host, also a man, pulled a similar stunt.
But if you're not quite game to hook your partner up to electrodes just yet, send him here instead. We've collected responses from women describing everything from morning sickness, to what contractions feel like, to lesser-known symptoms like twinging ligaments. Read on for what pregnancy feels like, and why it feels that way.
1. What morning sickness feels like:
How many movie heroines have realized they're pregnant after an unexplained bout of vomiting? Morning sickness is a classic pregnancy symptom — though it usually starts around the sixth week of pregnancy, by which time a woman has likely already missed a menstrual period and realized something might be going on. (Also, morning sickness is not always accompanied by vomiting, nor is it limited to the morning.)
Perhaps morning sickness gets its Hollywood cachet from the fact that it's easy to identify with. "It was like being hung over, without the fun the night before," said Kelly Nelson, a publicist in Vail, Co., who is pregnant with her first baby. "And it was almost constant."
Morning sickness is likely caused by rapidly changing hormonal levels, particularly a hormone called HCG, or human chorionic gonadotropin. HCG levels increase rapidly in early pregnancy and play a role in the signaling chain that causes the hormone progesterone to spike, which in turn makes the uterus a welcoming, blood-rich place for a fertilized egg to burrow.
Related: 10 Odd Facts About the Female Body
In early pregnancy, HCG levels are "supposed to basically double every two to three days," said Terry Hoffman, an OB/GYN at Mercy Medical Center in Baltimore. Pregnancy tests detect these HCG levels, which eventually drop off. In fact, Hoffman told LiveScience, a pregnant woman 36 weeks along can take a urine test for pregnancy and have it come back negative because her HCG levels are no longer so high.
2. What first-trimester fatigue feels like:
Even more common than morning sickness, but less heralded, is first-trimester fatigue, Hoffman said.
"Everyone gets ungodly tired," she said.
This can be tough for partners or friends to understand. A woman doesn't look pregnant yet (and may not have shared the news), but often feels as worn-down as she will throughout the entire pregnancy.
"The first trimester, I would feel fine one minute and the next second I would feel as if I hadn't slept in a week," Nelson said. Chores like cooking dinner or going to the grocery store felt like running a marathon, she added.
Running a marathon is a fair comparison, Hoffman said. Fatigue in early pregnancy is probably caused by the extra work a woman's body is putting into the pregnancy.
"When the sperm and the egg meet, everything becomes so metabolic," she said. Fortunately, the fatigue typically lifts by week 12 or 13 of pregnancy.
3. What growing breasts feel like:
Blossoming breasts are another pregnancy symptom. Some of the growth is caused by extra fat deposits laid down by the body in anticipation of gestation and nursing, Hoffman said; the rest is hormonally driven growth of the mammary tissue that will produce and deliver milk to the baby. Breasts often start swelling long before the baby bump, probably to ensure that a baby born early may be able to breast-feed, Hoffman said.
Unfortunately for partners, bigger breasts can be a bit of a tease, Hoffman said, because they tend to ache.
"It was painful," Nelson said. "It was like one of those things where if you blew on them, they hurt."
Hoffman said her early-pregnancy patients sometimes worry that the rapid breast growth they see in the first trimester will continue throughout the pregnancy. But they will stop growing, she said.
4. What relaxing joints feel like:
One of the odder pregnancy sensations is that of the joints relaxing. Birth involves getting a baby's large head through the pelvic opening. As part of this process, the body starts releasing a hormone called relaxin during pregnancy, softening the cartilage connection at the pubic bone called the pubic symphysis. Relaxin isn't targeted at this joint in particular, however, so it can make the rest of a woman's joints feel loose and unstable, too.
Relaxin can lead to aching sensations in the pelvis and other loosening joints, but that's a good thing, said Pamela Sailor, a California mother of a 2-year-old. Sailor said she didn't notice any pre-delivery loosening of her joints (pregnant women, don't fear: this is a rare occurance). For Sailor that meant her contractions during labor were not only pulling open her cervix at the head of the uterus, they were widening her pelvic bones. The resulting pain felt like the deep ache people with experience at the orthodontist might remember from getting their braces tightened.
"To me, that was so much more painful than any of the labor pains," Sailor told LiveScience.
5. What the weight gain feels like:
A woman who is normal weight will generally gain 25 to 35 pounds (11 to 16 kilograms) during pregnancy. On average, about 7.5 pounds (3.4 kg) of that is the fetus itself, according to the Olson Center for Women's Health at the Nebraska Medical Center. Another 1.5 pounds (0.7 kg) is the placenta. The breasts gain about a pound, and women usually add about 7.5 pounds (3.4 kg) in maternal energy stores, or fat. Another 3.5 pounds (1.6 kg) is water weight, and 3 pounds (1.4 kg) is blood. Yes, pregnant women have more blood — up to 50 percent more than they did before pregnancy.
So what does that weight gain feel like? It can be frustrating at first. Before women start obviously showing (at around 20 weeks for a first pregnancy), they may feel bloated and fat, or find their clothes don't fit.
Before pregnancy, the uterus is about the size of a pear and sits low in the pelvis, Hoffman said. By the time a woman is full-term, the organ weighs 12 to 14 pounds (5 to 6 kg) and extends up to the ribcage. Unsurprisingly, that front-loaded weight gain can stress the lower back and sometimes put pressure on the sciatic nerve, causing numbness and shooting pain down the leg. The baby bump can also get in the way of everyday activities.
"When you try to bend over, it's like there is a tent pole propped between your pelvis and ribs keeping you from folding over enough to reach your own shoes," Carol Millman, an animal trainer in British Columbia, wrote in an email to LiveScience.
6. What a baby kicking feels like:
Unlike aching joints or daily nausea, the feeling of the fetus moving is a pregnancy side effect most women welcome.
"It kind of shows you that there's a little peanut in there and everything else you're going through is worth it," Nelson said, describing the "flutters" she felt 21 weeks into her pregnancy.
Related: Gallery: Babies Yawning in the Womb
At first, baby's kicks are easy to mistake for gas bubbles, but they gradually grow in strength into unmistakable jabs (often causing visible seismic activity on the woman's abdomen). Millman described the sensation as having a "bag of snakes inside your stomach."
"And you are acutely aware of the fact that your abdomen has EARS because when loud noises happen it sets off the BAG OF SNAKES," she wrote in an email.
7. What stretching ligaments feel like:
Between 16 and 22 weeks of pregnancy, many women start experiencing round ligament pain, Hofmann said. Round ligaments are the anchors that run from the sides of the uterus down into the groin. The sensation is a sudden stabbing or twinge, similar to the ligament pain someone might feel if they cough or sneeze hard, she said.
8. What contractions feel like:
Though many don't know it, pregnant women start having contractions at around 12 weeks' gestation, Hoffman said. These "practice" contractions are called Braxton-Hicks, and they're rarely painful. Instead it feels like the uterus is getting hard and tight, "like a basketball," Hoffman said.
In labor, contractions feel more like menstrual cramps that increase in intensity. A more accessible starting point for men to understand the pain might be flexing a bicep and holding it for a long time.
"When you hold that flexion for a while, it starts to get crampy," Hoffman said. "That's kind of how it feels."
Contractions "weren't that bad," said Sailor, who decided against an epidural during her labor. "People make it out where you're just screaming your head off. It wasn't that bad. You live through it."
10. What giving birth feels like:
In the last stage of labor, when the baby's head is in position, it presses against the muscles of the rectum. The result, Hoffman said, is the feeling of having to pass a "bowling ball."
This sensation is usually accompanied by an intense urge to push.
"It was like a wave," Sailor said. "The beginning of it felt like it wasn't even a part of me."
Kat Khatibi, a wedding planner and photographer in Miami, Fla., had an emergency cesarean section to deliver her now 2-month-old.
"It felt like a whole bunch of pressure," Khatibi told LiveScience. The recovery was the most unpleasant part, she said. As with any abdominal surgery, it hurt to sit, stand and bend as the wound healed.
"It evens out, because it gave me a really good baby," Khatibi said. "She just doesn't complain."
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.