At 24 weeks, a fetus weighs about 1⅓ pounds (630 grams) and measures roughly 8¼ inches (21 centimeters) from the top of the head to the rump. That’s the curled-up measurement. Stretched out from head to heel, the length is closer to 12 inches, or about a foot long. In fruit terms, the fetus is comparable in size to an eggplant.
Weight and Length in Detail
Most of the weight at 24 weeks is still ahead. At this point, the fetus has gained enough bulk to feel substantial but remains very lean. Fat stores are just beginning to accumulate under the skin, which means the body still looks thin and somewhat wrinkled. Over the next 16 weeks, the fetus will gain roughly five to six more pounds as layers of fat fill out the skin and insulate the body for life outside the womb.
The crown-to-rump measurement of 8¼ inches captures the natural curled position. Obstetricians typically switch from crown-to-rump to crown-to-heel measurements around 20 weeks because the legs are now long enough to measure reliably. You may see either number quoted, which is why online sources sometimes look inconsistent for the same week.
What the Fetus Looks Like
The skin at 24 weeks is still translucent enough that blood vessels are visible beneath it. Very little subcutaneous fat has been deposited yet, so the body appears lean and angular. Fine hair called lanugo covers much of the skin, helping hold a waxy coating in place that protects against the constant exposure to amniotic fluid. Over the coming weeks, fat will gradually fill in, smoothing the wrinkled appearance and giving the skin a more opaque look.
Facial features are well defined by now. The eyes have formed but remain fused shut for a few more weeks. Eyebrows and eyelashes are present, and the ears have moved into their final position on the sides of the head.
Lung Development at 24 Weeks
The lungs are one of the last organs to mature, and at 24 weeks they’re in a critical stage of development. The tiny air sacs that will eventually exchange oxygen and carbon dioxide are forming, but they haven’t yet begun producing meaningful amounts of surfactant, the slippery substance that keeps air sacs from collapsing with each breath. Surfactant production increases substantially between now and full term. This is the primary reason extremely premature infants struggle to breathe on their own and often need breathing support.
Because the lungs are at this pivotal stage, 24 weeks sits right at what neonatologists call the “limit of viability,” the earliest point at which survival outside the womb becomes possible with intensive medical care. Survival rates at 24 weeks are significantly higher than at 22 weeks (where survival is around 11%), though still far below the 94% survival rate seen at 28 weeks. If preterm delivery looks likely, doctors often give steroid injections to help accelerate lung maturation before birth.
Sensory Development
By 24 weeks, the fetus can hear. Researchers first confirmed in the 1980s that babies begin processing sound while still in the womb, and studies have since shown that newborns prefer their mother’s voice immediately after birth, suggesting they’ve been listening and learning for weeks. At this stage, the fetus may startle in response to loud noises or shift position when you speak.
Vision is more limited but not absent. The womb isn’t as dark as you might assume. Human skin lets some light filter through, creating a dim environment roughly equivalent to a room with the lights off and curtains drawn. Research from the University of Lancaster found that third-trimester fetuses tracked light patterns shone into the womb and were twice as likely to follow patterns resembling a human face compared to random dot arrangements. At 24 weeks, the visual system is still maturing, but the groundwork for light detection is already in place.
Fetal Movement Patterns
Most people start feeling fetal movement around 20 weeks, and by 24 weeks those sensations are becoming more distinct. You might notice kicks, rolls, or rhythmic hiccups at various points during the day. Movement tends to be more noticeable when you’re sitting or lying still, partly because you’re paying closer attention and partly because your own movement can rock the fetus to sleep.
At 24 weeks, movements are still somewhat irregular. Formal kick counting isn’t typically recommended until the third trimester, around 28 weeks, when a noticeable decrease in activity can signal that something needs attention. For now, simply becoming familiar with your baby’s general activity patterns is useful. Movements will get stronger and more predictable as the fetus grows and runs out of room to tumble freely.
How Your Body Reflects the Growth
Your uterus at 24 weeks has expanded well above your belly button. Providers often measure fundal height, the distance from the top of the pubic bone to the top of the uterus, as a quick check on growth. After 20 weeks, the fundal height in centimeters roughly matches the number of weeks along you are. So at 24 weeks, expect a measurement of about 24 centimeters, give or take a couple. A measurement that falls well outside that range may prompt an ultrasound to check the baby’s size more precisely.