Uterus Position and Size: How Does It Change?

The muscle of the womb where your baby is living and growing is a very strong and flexible part of your body. As your pregnancy progresses, you’ll likely be hearing a lot about it – especially the uterus position. But what’s a normal uterus position anyway, and how does it change during pregnancy? Let’s take a look at how the uterus changes in size, shape and location over your pregnancy.

What is the normal position of the uterus?

Uterus Position

The uterus is roughly in the center of the lower abdomen between the navel and the crotch, and connected to both sides of the groin by round ligaments. It’s usually in the center of the pelvis, tilted slightly forward. This position is called anteflexion of the uterus.

If it’s tilted backward, it’s called retroversion or retroflexion of the uterus. About 10 – 20% of women have their uterus in the retroflexed position. Generally, this is simply a natural variation you are born with. However, in other cases it can be caused by another condition such as endometriosis. Your OB-GYN will be able to identify your uterus position through an ultrasound scan or pelvic examination, as well as its size and shape.

How does uterus position affect fertility?

There’s no direct link between the position of the uterus and fertility problems. However, some cases of retroflexed uterus are connected to endometriosis, which can make it more difficult to get pregnant. Symptoms of endometriosis include severe menstrual pain, heavy or prolonged periods, irregular bleeding, pain during sexual intercourse, and painful bowel movements. If this sounds familiar, see a doctor to work out what’s going on and how to deal with it.

How does the uterus position change during pregnancy?

fetus growth uterus

Before pregnancy, the uterus usually measures only around 7 cm long by 3 to 4 cm across (2.76 inches by 1.18 to 1.57 inches), with a thickness of just 1.5 to 2 cm (0.59 to 0.79 in), and it weighs just 40 grams (1.4 ounces). This puts the non-pregnant uterus at about the size of a chicken’s egg.

By the end of pregnancy, this will have expanded to a length of around 25 to 36 cm (10 to 14 in), and a thickness of roughly 20 to 22 cm (8.0 to 8.7 in). The uterus’ weight increases by around 20 times compared to its pre-pregnancy state, while its capacity grows to around 500 times its original volume. This is all to accommodate a full-term baby of about 46 to 51 cm (18 to 20 in) and 3.5 kg (7.5 pounds).

How does the uterus grow during pregnancy?

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The uterus doesn’t simply grow smoothly in proportion to how far along the pregnancy is progressing – it’s a response to factors like the size of the fetus and the amount of amniotic fluid.

The uterus begins to gradually increase in thickness after implantation. As you approach the second trimester in Week 13, the fetus is just under an ounce, and the uterus is about size of a grapefruit. In Week 28, the baby is under 3 pounds, but the following 10 weeks will see them roughly double in size. The uterus, in turn, suddenly expands to accommodate the rapid fetal growth towards the end of pregnancy. It takes about 6 months after birth for the uterus to gradually shrink back down to its pre-pregnancy size.

As your uterus grows and shifts position toward the end of pregnancy, the nearby abdominal organs also undergo changes. The bladder becomes longer and flatter as the uterus presses up against it. The growing uterus also puts pressure on the intestines, and the stomach is pressed up into an oblong shape. Even you heart and lungs are pushed up a little in your chest. These changes can cause a range of symptoms like frequent urination, constipation or diarrhea, heartburn, heart palpitations and breathlessness.

The uterus is what makes pregnancy possible

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Outside of pregnancy, symptoms like heavy periods or abnormal bleeding could be a sign of an irregular uterus position, so don’t hesitate to see a doctor to find out what’s going on in there. The more you know about your body, the better equipped you’ll be to make lifestyle choices that support your fertility goals. Understanding the uterus and its changes can also help you recognize and be prepared for the physical changes of pregnancy.