Premature Baby: What Are the Characteristics of a Preemie Baby?

What is Prematurity?

A premature birth—or preterm birth—happens when a baby is born three or more weeks early. Since the average full-term pregnancy lasts 40 weeks, a preterm birth is when a baby is born before the end of the 37th week. 

Doctors have categorized premature birth into three types, based on the number of weeks a baby has spent in the womb:

• Moderate or late premature birth: baby is born between 32 and 37 weeks
• Very premature birth: baby is born between 28 and 32 weeks
• Extremely premature birth: baby is born before 28 weeks 

These groupings help doctors and parents plan for the kinds of special health issues that certain premature babies may have.
You can learn more about the definition of prematurity by exploring Premature Birth 101 for moms.

Survival of Premature Babies

Preterm birth is one of the most common causes of newborn baby death. However, thankfully, advances in medicine mean that more preemie babies are able to survive today than ever before. Today in the US, babies born after 28 weeks and weighing more than 1 kilogram (2 lbs 3 oz) almost always live to go home. Survival rates are lower for those who are born very early. Every week a baby spends in the womb means a better chance of surviving. You can learn more about baby’s survival and how it improves every gestational week in this article from the American Journal of Obstetrics and Gynecology.

Characteristics of Premature Babies

In general, preemies born later in pregnancy look and act a lot like tiny full-term babies. Those born earlier tend to be smaller, thinner, and less able to function on their own. In time and with great medical care, however, premature babies start to fill out and look and act more like full-term babies.

How Your Premature Baby May Look

There are several traits that preemies often share:

• Many preemies are “low birth weight” or weighing less than five and a half pounds 
• Baby may seem smaller and thinner than average babies, with a head that seems large for their body
• Baby’s eyelids may stay closed until they reach about 30 weeks’ gestational age
• Premature babies may have thin, transparent-looking skin since they don’t have much body fat
• Baby may not have hair on their head, but they may have the fine body hair called lanugo that full-term babies grow—and then shed—in the womb
• Baby’s genitals may be small and not yet fully developed

 How Your Premature Baby May Act

Babies who are born closer to full term act more like average newborns, while those born earlier may seem different than other babies. Preemies tend to outgrow these differences as they get closer to their full-term age. Some ways that premature babies may seem different than full term babies:

• Baby may sleep more than other newborns
• Baby may have a weak-sounding cry
• Baby may be less able to keep a healthy body temperature since they have less body fat
• Baby may have trouble learning how to suck and swallow milk from the breast or a bottle, and they will need to eat more often than other babies.
• Baby may need help with their breathing if their lungs are not fully developed

Your Preemie’s Special Health Challenges

Premature babies face higher risks of some short- and long-term health problems than full term babies do. These issues are often worse for babies who are born very early or extremely early. The level of special care a preemie needs often goes along with how early and how small they are at birth.

This table lists some of the special health challenges that premature babies may face.

Body System	Possible Problems	Reasons for Problems
Respiratory (breathing)	Apnea (pauses in breath) Respiratory distress	Baby’s lungs may not be fully developed, which can lead to breathing problems
Immune	Higher chance of infections	Preemies often have immature immune systems, so they can’t fight off sickness as well as full-term babies can
Liver	Jaundice (a buildup of a substance called bilirubin in the blood that causes skin and eyes to look yellow)	An immature liver does not work as well as a mature one, so it can be hard for premature babies to get rid of bilirubin
Digestion	Necrotizing enterocolitis (damage to the intestines)	The digestive system of preemie babies can be more delicate and prone to injury than those of full-term babies
Heart and blood system	Patent ductus arteriosus (too much blood flowing into the lungs) Anemia (low red blood cell count)	When full-term babies are born, the blood vessel that sends blood away from the lungs in the womb usually closes by itself. In preemies, it may not close well, and that can cause heart and blood problems.

Read Michelle’s preterm birth story to learn more about the challenges of extremely preterm birth. See how one mother’s experiences inspired her to start a foundation to help other parents.

How is Premature Birth Managed in the Hospital?

Preemies need special health care that is not available at most community birthing centers. There are several levels of care available for premature babies in the US. Most premature babies who are born at 32 weeks or later and who weigh 3.3 lbs. or more can get treated at a Special Care Nursery, and those who are born earlier, smaller, and/or with health problems will need to spend time in a more specialized Neonatal Intensive Care Unit, or NICU.

While every baby has different health needs, here are some of the common treatments preterm babies often get in the hospital or intensive care unit:

• Warming beds called incubators help premature babies maintain their body temperature
• Doctors and nurses will keep track of baby’s vital signs like temperature, blood pressure, heart rate, breathing rate, and blood oxygen levels
• Special care in the intensive care unit often means giving extra oxygen and other breathing help when babies need it
• Intravenous (IV) therapy gives babies the extra fluids and medicines they need
• Preemies usually need help with special feedings; Babies who can’t yet suck or swallow can get milk through feeding tubes
• At the NICU or Special Care Nursery, premature babies also receive medical treatment for other health issues

When a preemie spends time in the hospital, the healthcare team gives daily updates to parents to let them know how the baby is doing with breathing, feeding, weight gain, and other important health factors.

The March of Dimes is a wonderful resource for parents who would like to learn more about prematurity and the milestones for premature baby development. They have many useful articles about the special health problems that many preemies face.

When Will My Preemie Be Allowed to Go Home?

There is no set weight or age that signals that a premature baby can go home from the hospital. Instead, the healthcare team will keep track of many signs of baby’s health and keep parents informed about when they might go home with baby. Doctors often give the original due date as a target, but babies must meet certain criteria before they can go home. Some of these include:

• Baby is breathing on their own; 
• Baby is eating without problems; 
• Baby is gaining plenty of weight; and 
• Baby is maintaining their body temperature like a full-term baby.

Effects of Prematurity on Mothers and Families

Caring for premature babies can be more demanding on families than caring for full-term newborns. It can be very stressful to worry about your baby and to split your time between home and the hospital. Bringing home your preemie when they are ready can be a wonderful experience, but it can also cause a lot of worry. 

For a firsthand account of the stress of prematurity, read Ashley’s preterm birth story. Her pregnancy experiences helped her develop the knowledge and skills to help other mothers facing the worry and uncertainty of premature labor.

If you are worried about preterm labor or caring for a premature baby, it’s important to know that you are not alone. There are great resources to help families get through this difficult time. For starters, the American Academy of Pediatrics has valuable information for dealing with the stress of caring for a premature baby. 

Typical Premature Baby Development

Preterm babies may be slower to grow and develop than babies who stayed in the womb for 37 or more weeks. One way to help parents understand the development of their premature baby is to compare them to babies at the same gestational age, rather than to those that were born at the same time. To do this, parents should adjust—or correct—baby’s age after birth.

How Do I Calculate My Baby’s Corrected Age?

After a preemie is born, parents and doctors will need to calculate a corrected age to gauge milestones for development. This means adjusting baby’s age to reflect how early he or she was born. If your baby was born at 32 weeks’ gestation, for example, you would subtract 8 weeks from his age for the first two years or so. So, if you have a preemie who was born 4 months ago but at 32 weeks (8 weeks early), his age would be corrected to 2 months. This will give you and your doctor a better idea of how baby is staying on track to reach his milestones.

Strategies for Preventing Premature Birth

Preterm birth is the most common pregnancy complication, affecting about one in ten pregnancies in the US. Throughout your pregnancy, it’s important to stay healthy and know your risk of preterm labor. It is important to complete all required prenatal tests as recommended by the CDC during your pregnancy. This helps your healthcare provider watch your baby’s development week by week and watch for any sign of complications. Adding the PreTRM Test to your prenatal testing regimen can also help assess the risk of a premature birth. Learn more about the PreTRM Test here.

Knowing Your Risk

While there are several reasons doctors know that some women may go into labor early, much is still unknown. Most premature births happen to women with no known risk factors. For more information about the risk factors for preterm birth, see PreTRM’s information on preterm birth risk factors.

The PreTRM Test for Risk Management is a blood test that your doctor can order for you during weeks 18 through 20 of pregnancy. It is available to most women who are pregnant with a single baby. PreTRM results help you understand if you are at higher-than-average risk of premature labor so you can work with your doctor to change your pregnancy care plans if needed to ensure the best possible outcome for your baby.

Learn more about the PreTRM Test with PreTRM FAQs.

Paying Attention to the Symptoms of Preterm Birth

Whether or not you are at a high risk for preterm labor, it is very important to know the signs and symptoms of preterm birth. If you have any of these symptoms during your pregnancy, call your doctor right away.

• Contractions every 12 minutes or more often
• Change in vaginal discharge
• Pelvic pressure
• Backache
• Cramps
• Other unusual changes

Learn more about strategies for preventing and managing premature birth here.