At 29 weeks, your baby is about the size of a butternut squash, measuring roughly 38.6 centimeters (just over 15 inches) from head to heel and weighing around 1.1 to 1.2 kilograms (about 2.5 pounds). You’re now in the early third trimester, and your baby looks much more like a newborn than the skinny, translucent figure from earlier ultrasounds. The skin is smoothing out as fat builds underneath, the eyes are open, and the brain is growing at a remarkable pace.
Size, Proportions, and Body Fat
The most visible change at 29 weeks is that your baby is filling out. Earlier in pregnancy, the skin hung loosely over a very lean frame. Now, layers of white fat are accumulating beneath the skin, rounding out the arms, legs, and cheeks. This fat serves two purposes: it will help regulate body temperature after birth, and it gives your baby that plumper, more newborn-like appearance. The skin itself is shifting from reddish and somewhat transparent to more opaque, though it’s still thinner than a full-term baby’s.
The head is more proportional to the body than it was in the second trimester, though it’s still relatively large. Fingernails have grown to the tips of the fingers, and toenails are forming. Fine hair called lanugo still covers parts of the body, but it’s starting to thin out. A waxy coating protects the skin from the amniotic fluid and will gradually diminish before birth.
Brain Development at 29 Weeks
The brain is in one of its most active growth phases. During the third trimester, the brain roughly quadruples in size, and its surface area increases dramatically as new folds and grooves form across the surface. These folds are what allow a large brain to fit inside the skull, and they’re a sign of increasing complexity. At 29 weeks, the brain is developing the networks that will eventually support temperature regulation, breathing rhythm, and coordinated movement.
This rapid brain growth is one reason why every additional week in the womb matters so much during the third trimester. The connections forming now lay the groundwork for sensory processing, sleep cycles, and the ability to feed after birth.
Eyes, Hearing, and Sensory Responses
Your baby’s eyelids opened around 26 weeks, and by 29 weeks the eyes can blink and respond to changes in light. Research using ultrasound has shown that fetuses in the third trimester will actually turn their heads toward light patterns projected through the uterine wall, particularly patterns that resemble a face. This suggests that even before birth, the visual system is active enough to detect and prefer certain shapes.
Hearing is also well developed. Your baby can hear your voice, your heartbeat, and muffled sounds from outside. Some parents notice that their baby startles or kicks in response to a sudden loud noise. The parts of the brain that process sound and vision are increasingly connected to higher brain regions, meaning your baby isn’t just detecting sensory input but beginning to process it in more organized ways.
Lung Development
The lungs are one of the last organs to fully mature, and at 29 weeks they’re still a work in progress. The tiny air sacs are forming but haven’t yet produced enough of the slippery substance that keeps them from collapsing with each breath. This is the main reason very premature babies need breathing support. Between now and about 36 weeks, the lungs will continue producing this substance in increasing quantities, making each additional week of pregnancy a meaningful step toward independent breathing.
Your baby is already practicing breathing movements, rhythmically drawing amniotic fluid in and out of the lungs. These aren’t real breaths (oxygen still comes through the placenta), but they exercise the muscles and structures that will need to work immediately at birth.
How Your Baby Moves at 29 Weeks
You’re likely feeling strong, distinct movements by now, though the character of those movements is beginning to shift. Earlier in the second trimester, you may have felt quick jabs and flutters. As space in the uterus gets tighter, many women describe the movements as more “slow motion,” with rolling, stretching, and turning sensations replacing the sharp kicks. That said, the frequency and intensity of movement shouldn’t decrease at this stage. Movements still feel strong and powerful, just different in quality.
You might notice patterns: your baby may be more active after you eat, when you lie down at night, or in response to sounds. Hiccups are also common and feel like small, rhythmic pulses in your belly. They’re caused by the diaphragm contracting as your baby practices breathing movements.
Position in the Womb
At 29 weeks, your baby still has room to change positions, and many babies haven’t settled into a head-down orientation yet. Breech position (feet or bottom down) is common at this stage and isn’t a concern. Most babies will rotate to a head-down position by about 36 weeks. Only 3% to 4% of babies remain breech at full term. If your provider mentions breech positioning at a 29-week visit, there’s plenty of time for the baby to flip on its own.
If a Baby Is Born at 29 Weeks
A baby born at 29 weeks has a strong chance of survival. Data from neonatal units puts the survival rate at roughly 84%, a significant jump from earlier weeks of gestation. However, a 29-weeker will need time in a neonatal intensive care unit, often several weeks to a couple of months, depending on how quickly the lungs mature and how well the baby can regulate temperature and feed independently.
The most common challenges for babies born this early are breathing difficulties, trouble maintaining body temperature, and feeding problems. Many will need help with breathing initially. Over time, as the lungs produce more of the substance needed to keep air sacs open and the brain matures enough to coordinate sucking and swallowing, these supports are gradually removed. Most 29-weekers go home around their original due date, though some are ready earlier.
What You Might See on an Ultrasound
If you have an ultrasound at 29 weeks, you’ll see a baby that looks recognizably human: a round head, defined nose and lips, fingers that open and close, and legs that may be tucked up or stretched out against the uterine wall. You might catch your baby yawning, sucking a thumb, or making facial expressions. The bones show up bright white on ultrasound, so you can often see individual ribs, the spine, and the small bones of the hands and feet. In 3D or 4D ultrasound, the face looks full enough to give you a preview of what your baby will look like at birth, though the cheeks and chin will continue to fill out over the remaining weeks.