At 16 weeks of pregnancy, your uterus is roughly the size of a small papaya or large orange, measuring about 14 to 16 centimeters (roughly 5.5 to 6.5 inches) from top to bottom. It has grown significantly from its non-pregnant size, when it weighs only about 6 ounces and is closer to the size of a small pear. By this point in your second trimester, the top of the uterus (called the fundus) sits about halfway between your pubic bone and your belly button.
How the Uterus Changes by 16 Weeks
Before pregnancy, the uterus is roughly 7 to 8 centimeters long and nestled deep in the pelvis. By 16 weeks, it has roughly doubled in length and expanded considerably in width and depth to accommodate a growing baby that is now about the size of an avocado. The uterus at this stage has shifted upward and forward out of the pelvic cavity, which is why many people start “showing” around this time.
This upward shift is also why certain early pregnancy symptoms begin to ease. The pressure on your bladder decreases somewhat as the uterus rises, so the constant urge to urinate that marked the first trimester often lets up for a few weeks. At the same time, your lower abdomen becomes noticeably firmer. If you press gently just below your navel, you can often feel the firm, rounded top of the uterus yourself.
Why Providers Don’t Measure Fundal Height Yet
You might expect your doctor or midwife to measure your uterus at a 16-week appointment, but formal fundal height measurements typically don’t start until around 20 weeks. Before that point, the top of the uterus hasn’t risen high enough above the pubic bone for a tape measure to give a reliable reading. Starting at 20 weeks, fundal height in centimeters roughly matches gestational age in weeks, giving providers a simple way to track growth at every visit.
At 16 weeks, providers rely more on a physical exam, feeling for the uterus with their hands, and on ultrasound measurements of the baby to confirm that growth is on track.
What Your Baby Looks Like Inside
The baby inside that expanding uterus is about 11 to 12 centimeters long (roughly 4.5 inches from crown to rump) and weighs around 100 grams, or about 3.5 ounces. There is still plenty of room to move, and many people start feeling the first flutters of movement around this time, especially if they’ve been pregnant before. The amniotic fluid surrounding the baby adds to the overall volume of the uterus, and that fluid volume will continue to increase for several more weeks.
Why Uterus Size Varies Between People
Not everyone’s uterus measures the same at 16 weeks. Several factors influence how large it is and how much it shows externally.
- Previous pregnancies: If you’ve been pregnant before, your uterine muscles and abdominal wall stretch more easily, so you may show earlier and feel larger than someone in their first pregnancy at the same stage.
- Carrying multiples: A uterus holding twins or triplets expands faster and measures larger than one with a single baby. By 16 weeks with twins, the uterus can measure several weeks ahead of a singleton pregnancy.
- Uterine fibroids: These noncancerous growths affect up to 80 percent of women by age 50. Most are small and cause no issues, but larger fibroids can add bulk to the uterus. In rare cases, fibroids grow large enough to make the uterus look months further along than it actually is.
- Body shape and height: A shorter torso gives the uterus less vertical room to grow, so it tends to push outward sooner. Taller people with longer torsos may not show as much at 16 weeks even though the uterus is the same size.
- Placental position: An anterior placenta (one attached to the front wall of the uterus) can make the belly feel firmer and look slightly larger, though it doesn’t change the actual uterine size.
Tracking Growth From Here
The uterus grows at a fairly predictable pace through the second and third trimesters. At 20 weeks, it reaches the level of the belly button. By 36 weeks, it sits just below the rib cage. In the final weeks before delivery, the baby often drops lower into the pelvis, and the fundus may actually measure a bit less than it did a few weeks earlier.
Between 16 and 20 weeks is when most people transition from regular clothes to maternity wear, simply because the uterus is expanding rapidly and the waistline changes week to week. If you feel like your belly seems bigger or smaller than what you see on other people at 16 weeks, that’s normal. The range of “showing” at this stage is wide, and it says very little about whether the pregnancy is progressing well. What matters most is consistent growth over time, which your provider will track at upcoming appointments.