All premature babies are small, require complex medical care, and may face serious complications both in the NICU and at home. Babies born very early will face far different complications from those born closer to their due date. Every week matters, so let’s take a closer look at how premature babies differ week by week. Premature babies born between 23 to 24 weeks gestation are called micro-preemies. They weigh just over a pound and measure about 8 inches long from their head to their bottoms. Babies born at this time will be covered by fine hair called lanugo, to keep them warm, as they have not yet developed brown fat. Their skin is also very thin and delicate. Although their eyes will most likely be fused shut, they’ll have fully developed eyelashes and brows. They will even have tiny fingernails. Most of the body’s systems are underdeveloped at 23 to 24 weeks gestation. The lower airways are only beginning to develop, which is why many 23-weekers and 24-weekers need respiratory support for long periods of time. By 26 weeks gestation, premature babies’ lungs are starting to develop alveoli, the air sacs that allow gas exchange. While they are still too young to breathe without help, this is a major milestone. Another developmental milestones for 25- and 26-weekers is the development of the startle reflex. A baby born at this time will startle at loud noises—a normal reaction of their nervous system. A baby’s footprints and fingerprints are also developing at this stage. By 28 weeks, premature babies weigh about 2 1/2 pounds and are about 16 inches long from head to toe. Rapid eye development is occurring. Premature babies born after 27 weeks can blink and no longer have fused eyelids. The retinas are still developing, which puts babies at risk for retinopathy of prematurity (ROP). Their eyes can form images at this stage. By 27 and 28 weeks, premature babies are also starting to develop more coordinated sleep/wake cycles and will have periods of REM sleep. At 29 to 30 weeks, premature babies weigh about 3 pounds and are about 17 inches long. While they’re still very small, 29-weekers and 30-weekers have more fat stored under their skin, making them look more like full-term babies. They are also starting to shed their lanugo (the fine hair that covers a preemie’s body). Their eyes can now blink, but bright lights and loud noises are usually still uncomfortable. In addition to all of this outside maturity, the brain goes through a period of rapid growth as well. The brains of 29- and 30-week premature babies are starting to look grooved and wrinkled. They are also mature enough to begin controlling body temperature. Also, at this time, a baby’s stomach and intestines are maturing and getting ready to digest milk. They are not yet ready to nipple feed (they will be fed through a tube), but can begin sucking on a pacifier to help develop their eating muscles. In addition to using the pacifier, kangaroo care while being fed will help your baby thrive. It can also help you bond with your baby.
Extremely preterm (less than 28 weeks)Very preterm (28 to 32 weeks)Moderate to late preterm (32 to 37 weeks)
Although they’re are still immature at birth and will require several weeks of NICU care, most infants born between 31 and 32 weeks quickly catch up to their peers and have few long-term effects of prematurity. Between 31 and 32 weeks, babies gain a lot of body fat. Premature babies born at this age are starting to look plump and may be able to maintain good body temperature without the help of an incubator. They use all five senses to learn about their environments but still may get overstimulated by bright lights and loud noises. Overstimulation by their environment may be expressed through a hiccup, sneeze, or cry. That being said, at this age, your baby will likely enjoy seeing your face up close. Parents usually want to know when their babies can come home from the NICU. Even though at this age, your baby looks like a tinier version of a full-term baby, your baby still needs special care, especially as their immune health continues to mature, and they develop their suck for feeding. While your baby will be awake more, their sleep needs to be protected, so they can continue to thrive and grow. Preemies born at 31 and 32 weeks may be able to do one or two of these things at birth, but it will take time (several weeks or more) to reach all three milestones. Although they are getting bigger, 33- and 34-weekers are still immature and may need to stay in the NICU for several weeks. However, the respiratory system doesn’t finish developing until the last weeks of pregnancy, and antibodies are only starting to pass from parent to baby—so preemies’ immune health is still a bit compromised. At 33 and 34 weeks, most premature babies will have fairly short NICU stays with only a few complications. They may need help breathing for a short time, but learning to eat may take the longest. The suck-swallow-breathe reflex is not well-coordinated, and these babies may not be strong enough to take in enough nourishment to grow and gain weight. During this time, it’s also important to watch out for signs of overstimulation from the environment like hiccuping, sneezing, crying, or arching away. Protecting your baby’s time for sleep is very important during this time. By the last weeks of pregnancy, most babies have turned to a head-down position. They have reached their full height, are gaining weight rapidly, have fingernails that come to the tips of their fingers, and have fully formed footprints. Their lungs won’t be completely developed for another couple of weeks, and they may not have enough fat to stay warm or enough strength to breast or bottle-feed effectively. Continuing to protect their sleep and time in the NICU until they are ready to go home is important.
