Being a new parent is already a lot to handle, but when a baby is born early, the job comes with its own set of special issues. But thankfully, due to a myriad of medical advances, even some of the tiniest premature babies born after 28 weeks have a good chance of surviving— and thriving. 

Keep in mind, however, that your premature baby may look and act differently than a full-term infant. To help you understand some of the short- and longer-term challenges your baby may face, here’s the definition of a premature baby as well as how she’ll appear and behave upon arrival.

What qualifies as a premature baby? 

By definition, preterm babies are born prior to their estimated due dates, coming into the world before the start of week 37 of pregnancy and before they’re developmentally ready. And it’s not just singleton babies that are born too soon. In addition to about 1 in 10 (roughly 10 to 13 percent) of babies in the U.S. being born prematurely, more than 60 percent of twins and nearly every set of triplets also comes early.

To break it down further, premature babies fall into categories, based on how soon they’re born:

  • Early term. Babies born between 37 and 39 weeks

  • Late preterm. Between 34 and 36 weeks, 6 days (most premature births occur at this stage)

  • Moderate preterm. Born between 32 and 34 weeks of pregnancy

  • Very preterm. Born between 28 weeks and 31 weeks (or less than 32 weeks)

  • Extremely preterm. Before 28 weeks of pregnancy

What is the survival rate for a premature baby?

A baby’s survival rate, also known as fetal viability, is an infant’s ability to live outside the mother’s womb. In general, doctors consider 24 weeks to be the tipping point in terms of viability, but even babies born at this age aren’t guaranteed to survive. Fetal viability at 24 weeks can range from 42 percent to 59 percent, according to the American College of Obstetricians and Gynecologists (ACOG).

Babies can survive when they're born before 24 weeks, but the rates aren’t encouraging. Indeed, every extra week in utero matters a great deal, statistically. For example, at 25 weeks, a baby has a 67 to 76 percent chance of viability. If the fetus makes it to 26 weeks, the odds of viability are even better, falling somewhere between 86 and 89 percent.

How much does a premature baby weigh?

A baby’s gestational age, or how far along in pregnancy you were before she was born, isn’t the only way an infant is assessed in terms of health and viability when she arrives. A premature baby’s weight is another important factor that’ll impact her care and the chance of complications.

Here’s a look at premature baby size categories that often determine how long she’ll need to stay in the NICU. As a general rule, the smaller the baby, the longer the hospital stay tends to be.

  • Low birth weight. This is considered less than 5 pounds, 8 ounces.

  • Very low birth weight. These babies weigh less than 3 pounds, 5 ounces.

  • Extremely low birth weight. Less than 2 pounds, 3 ounces.

  • Micro preemies. The tiniest and youngest (born before 26 weeks), these babies weigh less than 1 pound, 12 ounces.

How will my premature baby look when she’s born?

Depending on the category they fall into, preemies share some common characteristics, including in their appearance. The good news is that these distinctions usually fade as your baby ages. 

Here are some specific physical differences you may notice:

  • She may seem bird-like. Late preterm babies tend to look like smaller versions of full-term newborns. But preemies born at 32 weeks or younger haven’t developed much body fat, so they seem thin and fragile, with a small chest and skinny, bird-like arms and legs. 

  • Her head will appear big. Preterm baby heads may look larger in relation to their bodies. 

  • She may have pale or yellow-ish skin. Mottling, which may look blue, pale or blotchy, and jaundice, a yellowing of the skin, isn’t uncommon in premature babies in the NICU.

  • Her skin is thin and glassy. Some premature babies are born with skin that’s so thin, it's translucent because the extra fat barrier full-term infants are born with hasn’t formed yet. It can even make it possible to see the blood vessels under the skin’s surface.

  • She’s hairy. Her back and shoulders may be blanketed in tiny hairs called lanugo. These are usually shed before birth, but in many premature and some full-term babies, they’re still there.

How will my premature baby behave?

In addition to looking a little different from full-term babies, preemies tend to act differently too. Here's some of what you can expect from your premature infant:

  • You can hardly hear her cry. Many premature babies are born with immature respiratory systems, which means they might not have the hearty cry of a full-term infant. In fact, their cry may sound more like a whimper. 

  • She’ll need an incubator. Because of her lack of body fat, your preterm baby will feel chilled in a room where full-term babies won’t. To help warm her up and keep her body temperature on an even keel, she’ll likely be placed in an incubator (sometimes it’s called an isolette).

  • She’s super sleepy. Premature babies tend to snooze even more than full-term newborns, up to 22 hours per day — but only for an hour or so at a stretch, thanks to the need to fill their tiny tummies. Another difference: the quality of sleep. Preterm babies spend less time in deep sleep and are rarely fully awake— so expect your preemie to snooze for an hour, be drowsy for 20 minutes and so on (that drowsiness is another reason why it’s tough to feed a preemie). 

  • She’ll have labored breathing. Preemies may also have trouble getting oxygen to their internal organs and might be prone to having periods where they stop breathing, called apnea of prematurity. Luckily, doctors can help with special equipment like a ventilator or CPAP (continued positive airway pressure).

  • She'll hardly eat. Chances are, you won’t be able to feed your baby right away by breast or bottle. Younger preemies especially don’t have the muscle tone and coordination to suck, or they can do so for only short periods of time. Expect the doctor to insert a nasogastric (NG) tube through the baby’s nose to her tummy so she can receive small amounts of special preemie formula or expressed breast milk. 

  • But she’ll still eat frequently. Once your preemie is able to suck more efficiently, keep in mind that she’ll need to eat more often than full-term babies, about every hour to hour-and-a-half (versus every two hours), whether you’re nursing or bottle-feeding, because she’ll be taking in such small amounts at each feeding.

  • Many reflexes may be absent.  Because preemies have underdeveloped muscles and nerves, several reflexes typical for full-term newborns, including grasping, suckingrooting and the startle reflex, might not be there at birth.

  • She’s vulnerable to germs. Preterm babies aren’t able to fight bugs easily, so they are prone to infections during and after birth. That’s why it’s crucial to be scrupulous about washing your hands before you touch your baby. (In the NICU, it’s required of staff and visitors upon arrival. You may have to follow other protocols established by the hospital, such as wearing a mask.) Later, when you get home, limit the number of visitors your baby is exposed to (of course keep away anyone who’s sick) and have anyone who’s going to touch her scrub their hands before they do so. 

What health problems do premature babies have?

Premature babies may experience various complications at birth and there are some health concerns later in life too. Here’s a brief look at some of the potential issues:

Short-term health problems for premature babies

  • Breathing trouble. This is due to an immature respiratory system and, sometimes, a lack of surfactant that helps the lungs expand. Some preemies may develop a lung disorder called bronchopulmonary dysplasia and others develop apnea.

  • Heart issues. Low blood pressure is a concern, as is a heart defect caused by a persistent opening between the aorta and the pulmonary artery called a Patent Ductus Arteriosus.

  • Brain conditions. Bleeding in the brain may occur, which can be mild or wide spread.

  • Low body temperature. A lack of fat means your baby can’t regulate her own temperature and gets cold easily — and the result could be hypothermia.

  • GI issues. An immature gastrointestinal tract can lead to an injury of the cells in your baby’s bowel wall. Feeding your baby only breast milk can help lower the risk of this condition.

  • Anemia and jaundice. Not enough red blood cells can cause anemia and too much bilirubin in the blood may lead to newborn jaundice, a yellowing of the skin and eyes.

  • Hypoglycemia. This metabolic condition is due to low blood sugar and the inability to store and convert enough glucose in the body.

  • Infection. An immature immune system puts preemies at risk for infections — and if one reaches the bloodstream it may cause sepsis, a condition in which the body starts to damage its own tissues and organs.

Long-term health problems for premature babies

  • Cerebral palsy. This potential disability affects movement and posture.

  • Delayed learning. Premature babies may hit some developmental milestones later than full-term babies — and once school starts, there could also be learning disabilities.

  • Impaired vision. Retinal damage due to the swelling and scarring of the retina can affect vision and even cause blindness if left undetected.

  • Hearing loss and dental issues. Preemies may hear less well than full-term babies and their teeth may come in later, be misaligned or appear discolored.

  • Behavioral problems. Developmental delays and psychological issues are more common in premature babies than those carried to term.

  • Chronic conditions. Along with an increased risk of SIDS, preemies are also more likely to experience infections, asthma and feeding problems.

While the birth of a premature baby may fill new parents with concern, know that many of the conditions she’ll face are treatable. Your quick-to-appear bundle of joy may be smaller at first, but with good care and early intervention, she’ll likely thrive and blossom in her own time.