How Big Is My Uterus at 13 Weeks? | What to Expect

At 13 weeks, your uterus has risen above your pubic bone and is often compared to the size.

You’re 13 weeks along and starting to notice a small curve below your belly button. Maybe you’ve read that the uterus should feel like a grapefruit by now, but you’re not sure if that’s accurate for you.

Here’s what’s happening inside: Your uterus has grown upward and outward from the pelvis. The top part, called the fundus, now sits just above your pubic bone — about 3 to 4 inches below your navel. This is a normal and expected milestone for the end of the first trimester.

Where Is Your Uterus at 13 Weeks?

At 13 weeks, the fundus is positioned roughly 3 to 4 inches below your navel. You may be able to feel it as a firm, rounded shape when you press gently on your lower abdomen.

Your baby this week is about the size of a peach or a lemon — the NHS uses peach while What to Expect uses lemon. Even though the baby is still small, the uterus has expanded considerably from its pre-pregnancy size (about 1 inch thick and weighing around 1 ounce).

This upward growth means your bump may become more noticeable, especially when you’re lying down. It’s a sign your body is making room for the weeks ahead.

Why the Grapefruit Comparison Sticks

Pregnancy size analogies help paint a picture, even if they aren’t precise. The grapefruit comparison for a 13-week uterus is a common way to describe what’s happening inside your body.

• Pre-pregnancy shape and size: Before you were pregnant, the uterus was about 1 inch thick and shaped like an upside-down pear, weighing only about an ounce.
• Growth by 12 weeks: By the end of week 12, the uterus reaches the size of a grapefruit, according to the American Pregnancy Association.
• At 13 weeks location: The uterus now sits above your pubic bone, and you may feel the fundus about 3 to 4 inches below your navel.
• Baby size at 13 weeks: Your baby is roughly the size of a peach or a lemon. Its head makes up about half of its crown-to-rump length.
• What this means for you: You might notice a lower belly bump, especially in clothes that fit snugly. Your provider can likely feel the fundus during a prenatal check.

These comparisons aren’t meant to be exact — uteruses vary from person to person. But they give a helpful general picture of the changes happening.

How Uterus Size Relates to Baby Size

The uterus grows to accommodate your baby, but its size at 13 weeks reflects more than just the baby’s length. Your body is also adding muscle tissue, blood vessels, and amniotic fluid.

Many expecting parents wonder about big uterus weeks, and the grapefruit analogy is a rough guide. Every pregnancy develops a little differently, and your provider can tell you what’s normal for your situation.

According to WebMD, you can often feel the top of your uterus about 3 to 4 inches below your navel at this stage. The medical chart for uterus location at 13 weeks confirms this pattern.

These analogies give a sense of scale, but your own anatomy, muscle tone, and whether this is your first pregnancy can affect when and how your bump shows.

What Your Provider May Check at 13 Weeks

At your 13-week appointment, your provider will likely look for signs that your uterus is growing on track. Here’s what they may do.

1. Feel the fundus: They may press gently on your lower abdomen to locate the top of your uterus. At 13 weeks, the fundus should be felt just above your pubic bone.
2. Discuss fundal height measurement: While fundal height (distance from pubic bone to fundus) is typically measured after week 20, some providers may palpate to confirm size.
3. Assess via ultrasound: An ultrasound around this time can measure baby’s crown-to-rump length and head size, offering a more exact growth picture.
4. Check for discomfort: As your uterus stretches, you may feel round ligament pain or a pulling sensation. That’s common, but your provider can rule out other causes.
5. Consider multiples: A fundus that feels larger than expected may suggest twins or more, so your provider may look for signs of a multiple pregnancy.

These checks help ensure your pregnancy is progressing as expected. A variation of about 2 cm in fundal height later in pregnancy is considered normal.

Understanding Fundal Height and What It Means

Fundal height is the distance from the top of your pubic bone to the top of your uterus. It’s a simple screening tool that helps track growth, especially after week 20.

At 13 weeks, fundal height isn’t usually measured yet because the uterus is still low in the pelvis. But learning about it now helps you understand what your provider will look for later. The Open University’s guide on fundal height at 13 weeks explains how this measurement is used to estimate gestational age and growth.

Later in pregnancy, fundal height in centimeters is expected to be close to the number of weeks, give or take 2 to 3 cm. A larger measurement may suggest fetal macrosomia (a larger-than-average baby) or increased amniotic fluid, though many other factors can influence it.

A single measurement doesn’t tell the whole story. Your provider will consider your pre-pregnancy size, baby’s position, and any other factors that could affect the number.

The Bottom Line

At 13 weeks, your uterus is about the size of a grapefruit and rests just above your pubic bone, often about 3 to 4 inches below your navel. Your baby is roughly the size of a peach or lemon. Every bump looks a bit different, and that’s entirely normal. Your provider can confirm your uterus is growing as expected through a quick feel or ultrasound.

If you have any concerns about your belly size or feel unusual pain, your obstetrician can measure your fundal height or order an ultrasound to make sure everything is on track for your specific pregnancy.