At 24 weeks pregnant, your baby measures about 8.25 inches (21 cm) from head to rump and weighs roughly 1.3 pounds (630 grams). Measured from head to toe with legs extended, that puts your baby at around 12 inches long, or about the size of an eggplant. This is a milestone week for several reasons, from lung development to the threshold of viability outside the womb.
Weight and Length at 24 Weeks
The standard measurement for fetal length at this stage is crown to rump, meaning from the top of the head to the bottom of the tailbone. By that measure, your baby is about 8.25 inches. If you include the legs, the total length is closer to a foot. Weight has been climbing quickly and will continue to: your baby has roughly tripled in weight since week 16, and will nearly triple again between now and birth.
Much of the weight gain at this point comes from fat deposits beginning to form under the skin. Until now, your baby has been quite lean. Over the coming weeks, layers of fat will fill out the body and help regulate temperature after birth. Muscle and bone are also getting denser, which you may already be noticing as kicks and movements feel stronger and more defined.
What’s Developing This Week
The lungs hit an important turning point around 24 weeks. Specialized cells in the lungs begin producing surfactant, a slippery substance that keeps the tiny air sacs from collapsing. Without surfactant, the lungs can’t exchange oxygen properly. This is why babies born before 24 weeks face much steeper odds: their lungs simply aren’t ready to function. Surfactant production will continue ramping up for the rest of the pregnancy, but the fact that it’s beginning now is a major developmental marker.
Your baby’s hearing is also well established by now. Fetuses can start picking up sounds around 20 weeks, though the amniotic fluid and surrounding tissues muffle everything, filtering out higher-pitched sounds. What gets through most clearly are low-frequency noises: your heartbeat, the rumble of your voice, deep environmental sounds. Your baby is already learning the rhythm and tone of your speech patterns, which is why newborns can recognize their mother’s voice at birth.
The brain is growing rapidly, forming the grooves and folds that increase its surface area. Sleep-wake cycles are becoming more regular, and your baby likely has periods of active movement followed by stretches of quiet rest. You may start to notice a pattern to when your baby is most active.
Why 24 Weeks Is a Viability Milestone
In neonatal medicine, 24 weeks is widely considered the threshold of viability, the point at which a baby born prematurely has a realistic chance of survival with intensive medical care. The survival rate for infants born at 24 weeks is between 60 and 70 percent. Before 24 weeks, the odds drop below 50 percent.
Survival and health aren’t the same thing, though. About 40 percent of extremely premature babies face long-term health complications, including issues with breathing, vision, hearing, or neurological development. The earlier a baby is born, the higher those risks climb. Every additional week in the womb makes a meaningful difference in outcomes, which is one reason your medical team monitors closely for signs of preterm labor from this point forward.
What You Might Be Feeling
Your uterus now reaches about 24 centimeters above your pubic bone, give or take 2 centimeters. Your provider may start measuring this distance (called fundal height) at your appointments. It’s a quick check to confirm the baby is growing on track. The measurement in centimeters generally matches your week of pregnancy, so at 24 weeks, around 24 centimeters is expected.
You’re likely feeling the baby move consistently now, and partners or others may be able to feel kicks from the outside. The growing uterus can press on your lower back, bladder, and digestive system, making back pain, frequent urination, and heartburn common companions at this stage. Some women also notice swelling in their feet and ankles as blood volume continues to increase.
The Glucose Screening Test
Somewhere between 24 and 28 weeks, you’ll be offered a glucose screening test to check for gestational diabetes. The most common version involves drinking a sugary liquid and having your blood drawn one hour later. You don’t need to fast or change your diet beforehand. If the result comes back elevated (above 140 mg/dL), you’ll be asked to return for a longer, more detailed test that involves fasting overnight and having blood drawn multiple times over three hours.
Gestational diabetes affects how your body processes sugar during pregnancy and can lead to a larger-than-average baby, complications during delivery, and health risks for both you and your baby if unmanaged. The good news is that when caught early, it’s typically well controlled through dietary changes, exercise, and sometimes medication. If you haven’t been scheduled for this test yet, expect it at your next few appointments.