At 27 weeks, a baby in the womb weighs about 2¼ pounds (1 kg) and measures roughly 13¾ inches (35 cm) from head to heel, comparable in size to a head of cauliflower. The skin is still reddish and somewhat wrinkled, but body fat is starting to fill out beneath it, giving the baby a plumper, less fragile appearance than just a few weeks earlier. This is a milestone week for several reasons: the eyes can now open and blink, eyelashes are in place, and the brain is on the verge of a major leap in sleep-cycle development.
Skin, Hair, and Overall Appearance
Earlier in the second trimester, a baby’s skin is almost see-through, with veins clearly visible underneath. By week 27, the skin is still translucent but noticeably less so. Increasing deposits of body fat are smoothing out some of the wrinkles and giving the skin a slightly less red tone. Full opacity doesn’t arrive until closer to 32 weeks, so at this point you’d still see a network of tiny blood vessels if you could peek inside.
A fine, downy hair called lanugo covers most of the body. It first appeared around 21 weeks and will stay until the final weeks of pregnancy, when it gradually sheds. The baby also has visible eyebrows and eyelashes, both of which formed by about 26 weeks. Some scalp hair is growing in too, though how much varies widely from baby to baby. A waxy, white coating called vernix caseosa protects the skin from the amniotic fluid, and patches of it may still be visible at birth.
Eyes and Sensory Development
Week 27 marks one of the more exciting milestones: the baby can now open and close its eyes. The eyelids, which were fused shut for months, separated around 26 weeks as the nerve pathway connecting the eyes to the brain’s processing centers became established. By 27 weeks, the baby blinks and the eyelashes frame fully formed eyes. Research using ultrasound has even shown that fetuses at 26 weeks begin tracking light patterns projected through the uterine wall, with a measurable preference for face-like arrangements of light dots over random ones.
Hearing is also well developed by this point. The baby responds to loud sounds and may startle at sudden noises. Many parents notice that music, conversation, or a dog barking triggers a kick or shift in movement.
Movement and Position
Between 25 and 28 weeks, the nature of fetal movement starts to change. Earlier flips and full-body rolls give way to more defined kicks, stretches, squirms, and jerky movements. There’s still enough room in the uterus for the baby to shift between head-down, feet-down, and sideways positions, and many babies rotate frequently around 28 weeks. You don’t need to worry about which direction the baby is facing yet; there’s plenty of time for it to settle head-down before delivery.
This is also the stage when many providers suggest you start paying attention to patterns of movement. You’ll likely notice your baby is more active at certain times of day, often when you’re resting or lying down at night.
Brain Development and Early Sleep Cycles
The brain is undergoing rapid changes at 27 weeks. Eye movement activity, which researchers track with ultrasound, increases significantly between 24 and 29 weeks. By about 28 to 29 weeks, body movements and eye movements begin to synchronize during sleep, creating what’s known as “active sleep.” This is considered a precursor to REM sleep, the dreaming phase familiar in adults. The brain centers responsible for this coordination are just switching on, which means at 27 weeks the baby is right on the cusp of developing organized sleep and wake cycles rather than drifting in and out of consciousness randomly.
This neurological leap has practical implications. Babies born very prematurely before these sleep centers mature face additional challenges with brain organization. At 27 weeks, the wiring is almost there but not yet fully functional.
Lung Development
The lungs are one of the last organs to mature, and at 27 weeks they’re in an active stage of preparation. The cells responsible for producing surfactant, a slippery substance that keeps the tiny air sacs from collapsing, are differentiating between 24 and 34 weeks. At 27 weeks, surfactant production is underway but not yet at the level needed for independent breathing. The air sacs themselves won’t reach their final number and size until well after birth, continuing to multiply up to about three years of age.
This is why lung support is the primary concern for babies born at this stage. The lungs can function with medical help, but they aren’t ready to work on their own.
What Happens If a Baby Is Born at 27 Weeks
A baby born at 27 weeks is considered very preterm but has a strong chance of survival with neonatal intensive care. Survival rates in published studies range from roughly 77% to 90%, depending on the medical center and the individual circumstances. Factors like the baby’s sex (girls tend to fare slightly better), the presence of infection, and whether the mother received steroid injections before delivery all influence outcomes.
Babies born this early typically need help breathing, regulating body temperature, and feeding. The most common complications that medical teams watch for involve the lungs, the brain’s blood vessels, and the digestive system. A NICU stay of several weeks to a few months is standard, with the goal of getting the baby to the developmental point it would have reached inside the womb.
How 27 Weeks Compares to Nearby Weeks
Development in the third trimester moves fast. At 25 weeks, the baby is noticeably thinner and the skin is more wrinkled. By 27 weeks, added fat is softening the appearance. By 32 weeks, the skin loses its translucency entirely, and by 36 weeks the lanugo has mostly disappeared, replaced by a fuller head of hair in many babies. Weight gain accelerates sharply in the coming weeks: the baby will roughly triple its current weight before birth.
At 27 weeks, the baby looks recognizably like a newborn but in miniature, with proportionally large eyes, visible eyelashes, and skin that’s still working toward its final layers of insulating fat.