At 24 weeks of pregnancy, your baby looks unmistakably human. Weighing roughly 1.3 pounds and measuring about 12 inches from head to heel (about the length of an ear of corn), a 24-week baby has fully formed facial features, visible hair, and thin but proportionate limbs. This is a milestone week: the baby is considered viable outside the womb, though still very premature.
Size and Proportions
A 24-week baby is slender. Most of the body fat that fills out a newborn’s cheeks and limbs hasn’t been deposited yet, so the skin appears wrinkled and somewhat translucent, with blood vessels visible beneath the surface. The head is still large relative to the body, but the torso, arms, and legs have caught up enough that the overall proportions are starting to resemble those of a full-term baby. Fingers and toes are fully formed, complete with tiny fingernails.
Skin, Hair, and Facial Features
The skin at 24 weeks is covered in a fine, downy hair called lanugo, which helps hold a waxy white coating (vernix) in place. That coating protects the skin from constant contact with amniotic fluid. The skin itself is reddish-pink and quite thin, since the fat layers underneath are still building up.
Eyebrows and eyelashes have formed by this point, and some babies already have visible hair on their scalps. The eyes are fully developed in structure, though the irises don’t yet have their final pigment. The eyelids, which were fused shut earlier in pregnancy, are beginning to open. The nose, lips, and ears all have distinct, recognizable shapes, and the ears have nearly reached their final position on the head.
What the Baby Can Do
A 24-week baby is surprisingly active. You’re likely feeling regular kicks, rolls, and stretches by now, and some of that movement is a response to the outside world. The inner ear is nearly fully developed, so your baby can hear your voice, your heartbeat, and rhythmic internal sounds like blood flowing through the placenta. Those sounds arrive muffled, similar to hearing underwater. As early as 22 weeks, babies begin reacting to their mother’s voice by moving their arms, legs, and head. Voices and noises from outside the womb are audible too, but the reaction is typically less pronounced because those sounds pass through more tissue and fluid.
Sleep-wake cycles are starting to emerge around this time. You may notice periods of activity followed by stretches of quiet, which correspond to your baby cycling between rest and wakefulness.
Brain Development
The brain is growing rapidly during the second and third trimesters. Nerve fibers connecting different parts of the brain’s outer surface are actively forming, and the brain is beginning to develop the folds and grooves that characterize a mature brain. Specialized cells are still guiding new neurons into position, a process that will continue for several more weeks. Short-range connections between neighboring brain regions are strengthening, building the foundation for more complex processing later in pregnancy.
This rapid wiring is one reason the final trimester matters so much for brain development. At 24 weeks, the architecture is being laid down, but the fine-tuning is far from complete.
Lung Development
The lungs are one of the last major organs to mature. At 24 weeks, the tiny air sacs are forming, and the lungs are beginning to produce surfactant, a mix of protein and fat that keeps air sacs from collapsing when a baby breathes. Production is still low at this stage and increases steadily as the pregnancy continues. This is the single biggest challenge for babies born at 24 weeks: the lungs are functional enough to sustain life with medical support, but not yet ready to work independently.
Viability Outside the Womb
Twenty-four weeks is widely recognized as a critical threshold for survival outside the womb. A large study of nearly 11,000 babies born between 22 and 28 weeks, published by researchers at Stanford Medicine, found that about 78% survived when born between 2013 and 2018, an improvement over earlier years. Survival rates at exactly 24 weeks are lower than the overall range but have climbed significantly over the past two decades.
Babies born this early need intensive care. Because their lungs produce limited surfactant, they typically receive breathing support, often through gentle devices that keep the airways open rather than mechanical ventilators, which can damage fragile lung tissue. Prenatal steroids given to the mother before delivery help accelerate lung and organ maturation and reduce the risk of complications like brain bleeding.
Neonatal intensive care units also focus on recreating a womb-like environment: low lighting, minimal noise, and limited disruption. Skin-to-skin contact between parents and baby (sometimes called kangaroo care) has been shown to increase weight gain, lower the risk of severe infection, and improve both survival and brain development. A baby born at 24 weeks would typically spend several months in the hospital before going home.
How 24 Weeks Compares to Later Stages
If you looked at a 24-week baby next to a full-term newborn, the most obvious differences would be size and body fat. A full-term baby weighs roughly five times more. The 24-week baby’s skin is thinner, redder, and more wrinkled because the fat that smooths everything out accumulates mostly in the third trimester. The limbs are thinner, and the overall frame is delicate.
Over the next 16 weeks, the baby will gain about 6 more pounds, the lanugo will mostly shed, the skin will thicken and become opaque, and the lungs will mature enough to breathe air independently. But at 24 weeks, the basic blueprint is complete. Every major structure is in place. What remains is growth, fat deposition, and the fine-tuning of organs, especially the brain and lungs, that need more time to work on their own.