9 Weird Facts About Your Uterus Every Woman Needs to Know

The powers of this reproductive organ go beyond pregnancy.

Your uterus is one of the stars of the show during pregnancy. And when your period hits every month, it makes its presence known by leaking blood and sidelining you with cramps. The rest of the time, this pear-shaped organ in the middle of your reproductive system pretty much lays low.

But just because your uterus isn't one of those drama queen body parts always demanding attention doesn't mean there isn't a lot more to know about it. From the role it plays during sex to why some women have two uteruses to the scientific frontier of uterus transplants, we asked ob-gyns to fill us in on some fascinating uterus facts.

It's usually no bigger than a pear

When a woman is not pregnant, the uterus is only about 3 inches long and 2 inches wide—roughly the size of a pear, an orange, a smartphone, even your fist—though the exact size varies among women, Christine Greves, MD, an ob-gyn at Orlando Health in Florida, tells Health.

It can expand to the size of a watermelon

The uterus is one hell of a stretchy organ. If you do conceive, it starts expanding...and then expanding more. During the first trimester, it's more like a grapefruit. As the baby grows, so does the uterus; in the second trimester it's papaya-size, and by the end of the third trimester, it resembles a watermelon, according to the American Pregnancy Association. After birth, it takes about 6 weeks to deflate back to its orignal dimensions, a process called involution.

Some women are born with two uteruses

Uterus didelphys is a very rare congenital condition that leaves a woman with two distinct uteruses. The abnormality happens during fetal development, when the two tubes that are supposed to join together to form one uterus develop into separate structures, according to Mayo Clinic. Women with uterus didelphys might also have two cervixes and two vaginas.

"Usually when you have two [uteruses], one is going to be more prominent than the other one," Tristan Bickman, MD, an ob-gyn in Santa Monica, California, tells Health. Dr. Bickman states that uterus didelphys isn't typically diagnosed untll a woman becomes pregnant, and many times the discovery explains pregnancy complications or fertility issues.

Others don't have one at all

Mayer-Rokitansky Küster-Hauser syndrome (MRKH) is the name of another rare congenital condition that causes a woman to be born without a uterus or vagina, though the external genitalia look perfectly normal. Women who have MRKH don't get their period, and they can't become pregnant—though they have normal ovaries and ovarian function. It's not known what causes the disorder. "It's like being born with one kidney instead of two...who knows why?" Dr. Bickman says.

Some uteruses are shaped like a heart

A heart-shaped uterus is called a bicornuate uterus. Instead of being pear-shaped, the uterus has two bumps sticking up that make it resemble a heart. Approximately 1 in 1,000 women have a bicornuate uterus. It's a congenital abnormality with no symptoms, and it doesn't seem to affect menstruation. Still, one study has shown that women with a bicornuate uterus are at higher risk of miscarriage, premature birth, and breech birth.

Others are "tilted"

This type of uterus is also called a tipped or retroverted uterus, but tilted seems to be the most popular term. For most women, the uterus sits in the pelvis tipped slightly toward the front of the body, according to the National Institutes of Health. But for one in five women, it tilts backward.

A tilted uterus is something a woman can be born with, or it may be the result of scar tissue in the pelvis caused by endometriosis or an infection. in general, it shouldn't effect your periods or fertility...just one of those fun body quirks your ob-gyn might inform you about.

Your uterus plays a part in your sex life

Some women say that their uterus helps make sex more pleasurable. "I have had some patients be very hesitant about a hysterectomy because the uterus is an important part of their sensation of their orgasm, and not many women can say that," says Dr. Greves.

Science doesn't definitively explain what's going on here, but it might have to do with the cervix, the passageway that connects the uterus to the vagina. Some women enjoy feeling their partner's hand or penis against their cervix, and there's even something called a cervical orgasm, too. Since the cervix and uterus are connected, cervical stimulation can trigger pleasurable sensations on or near the uterus.

The pleasure could also come from the uterine contractions that happen after an orgasm, which seems to encourage sperm to get closer to the egg for fertilization, says Dr. Greves.

Uterine cancer is on the rise

Uterine cancer is the fourth most common cancer in the United States—and the seventh most common cause of death from cancer in the U.S. Even worse, it appears to be on the rise, according to a 2018 report from the Centers for Disease Control. When people think of the cancers that strike women, they list breast cancer, ovarian cancer, and cervical cancer, though uterine cancer is the most common of these. "I've diagnosed a few cases just in the past couple of months and it's sad," says Dr. Greves. The most prevalent type of uterine cancer is cancer of the uterine (or endometrial) lining.

The reason for the rise isn't established. But according to the National Cancer Institute, women who are overweight or obese are two to four times as likely as healthy-weight women to develop endometrial cancer. What's the connection between weight and this form of cancer? Heavier people are at a higher risk because fat cells have high estrogen levels, says Dr. Greves.

Uterus transplants are now possible

Doctors have performed successful uterine transplants on 11 women—each of whom received a uterus from a living or deceased woman, had the transplant surgery, and went on to conceive and give birth. It's pretty amazing, but it's extremely difficult surgery, thanks in part to the odds of rejection and all the blood vessels in the pelvic region. Once a woman with a donor womb is done having kids, the transplanted womb is supposed to be removed, Health previously reported.

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