The Top 10 Interesting Facts About Premature Babies: How Premature Birth and Prematurity Affect Your Baby

1. Premature Babies Are Classified by How Early They Were Born

On average, most full-term pregnancies last about 40 weeks. When a baby is born before the end of the 37^th week, the birth is considered to be preterm or premature. Because the health needs of preemies tend to depend on how early they are born, researchers and doctors have created three main categories based on how long the pregnancy lasted. These are:

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

While no two premature babies face the exact same set of challenges and treatments, these categories help doctors and parents understand the types of complications  that preemies may face, based on how early they arrive.

2. Preterm Birth is the Most Common Pregnancy Complication: About One in Ten Births in the United States is Premature

In the United States, about one in ten pregnancies ends before the end of the 37^th week¹. This makes it the most common pregnancy-related complication in the country. Preterm birth is more common than many well-known pregnancy outcomes:

Condition	Prevalence
Preterm Birth	1 in 101
Preeclampsia	1 in 302
Down Syndrome	1 in 7003
Cystic Fibrosis	1 in 3,5004

The rates of premature births vary worldwide. For more information about prematurity around the world, check out the World Health Organization’s Preterm Birth FAQ sheet.

3. The Health Problems Preemies Face are Often Linked to How Early They Are Born

While all premature babies are different, those who are born earlier have more health issues than a preterm baby  who arrives closer to her due date. 

Because of great advances in medicine, more and more preemies are surviving. In a recent study, 78% of babies born between 22 and 28 weeks survived in 2018, up from 76% in 2012. The same US study showed vast differences in survival for those who were born at 28 weeks: 94% lived to leave the hospital, compared to only 11% of those born at 22 weeks.

The medical challenges faced by preemies are connected to the development they miss out on in the womb, so these complications  tend to be more severe in babies who are born extremely early.

Development in the Womb	Possible Problems for Premature Babies
Fat stores that develop late in pregnancy help babies maintain their body temperatures	Preemies often need help maintaining a healthy body temperature
Digestive system development in the womb allows babies to eat after birth	It can be difficult for preemies to suck, swallow, and digest food for proper nutrition
Lungs finish developing in the womb late in pregnancy to prepare babies for their first breath	Premature babies may have breathing problems, like apnea (stopping breathing) and respiratory distress
Babies develop a working immune system in the womb to help fight off infections	Preterm babies may have a harder time avoiding infections
The heart and blood system finish developing near the end of pregnancy	Premature babies may face heart troubles, blood pressure problems, or issues with their red blood cells
The brain and nervous system continue to mature during a full-length pregnancy	Preterm babies may have brain bleeding, seizures, or a disease of the eye called retinopathy if they are born extremely early

The March of Dimes has more details on some of the health issues that preemies commonly face. To learn more about fetal development, explore our week-by-week guide.

4. There Are Four Different Types of Newborn Care Hospital Units

You may have heard the term NICU, or Neonatal Intensive Care Unit. There are actually four levels of care that newborns can get, based on how early they are born and the kinds of health complications  they face.

Well Newborn or Level I Neonatal Care. 

A Level I Unit is a hospital nursery that provides basic care for newborns. They can also help sick or premature babies get ready to move into a higher level nursery.  

Special Care Nursery or Level II Neonatal Care.

A Level II neonatal unit gives premature babies care they wouldn’t be able to get in a Level I nursery, like help with mild breathing complications  and feeding. The Special Care Nursery often helps preemies who are born at 32 weeks of pregnancy or later and who weigh 3.3 lbs. or more. 

Neonatal Intensive Care Unit (NICU) or Level III Neonatal Care.

A NICU gives a higher level of care for preemies who are born before 32 weeks and/or who weigh less than 3.3 lbs. NICUs are run by neonatologists (newborn specialists) who work with a whole team to help babies get bigger and stronger. 

Regional NICU or Level IV Neonatal Care.

Regional NICUs have all the tools of a Level III NICU and can also provide surgery to newborns. 

For more information on the types of care preemies often receive, check out our blog about premature birth.

5. Kangaroo Care is a Real Medical Treatment to Help Preemies Grow and Thrive

When a premature baby is in the hospital, it can be an overwhelming experience for parents. They may often feel helpless as they watch nurses and other professionals caring for their babies. 

There is one very important medical treatment that mothers and fathers can give, called kangaroo care or kangarooing. With kangaroo care, the baby is placed on the adult’s chest, where they can have direct skin-to-skin contact with their child. The baby will be dressed in only a diaper and hat, and the adult will have no shirt on. A blanket is then placed over both of them for warmth. 

Kangaroo care provides many health benefits:

• Bonding for babies and parents
• Helping steady baby’s heart rate
• Helping baby breathe better and make better use of oxygen in their body
• Improving baby’s sleep
• Helping baby gain more weight
• Calming baby
• Helping mom’s milk supply come in
• Growing parents’ confidence in caring for baby

To learn more about kangarooing for preemies, check out this excellent resource from the Cleveland Clinic.

6. The Most Common Therapies in the NICU Involve Body Temperature,  Breathing, and Feeding

When premature babies are in a Special Care Nursery or NICU, they will be monitored so the nurses and doctors can keep track of vital signs like temperature, pulse, breathing, blood pressure, and blood oxygen levels. When these measurements slip outside of normal ranges, an alarm will sound to let the staff know they should check on the baby and give them the care they need. While all babies are different, here are some of the most common medical treatments preemies receive in the hospital:

• Temperature maintenance. Warming beds called incubators help preemies maintain the best body temperature. There are a few main types of incubators in NICUs:
  • Open box incubators. These heated beds are open so that the staff can care for baby quickly.
  • Closed box incubators. These are enclosed beds that help maintain the right temperature and humidity for baby.
  • Portable incubators. These are special beds that can be used to move baby to another area of the hospital, or into an ambulance to move to a different hospital.
• Oxygen therapy. Care for premature babies often includes giving extra oxygen when needed.
• Intravenous (IV) fluids. Many preemies will have IVs in place. These help doctors give babies the extra fluids and medicine they may need.
• Feeding. Babies born prematurely usually need help with special feedings. At first, breast milk or formula is given through a tube in the stomach for babies that can’t yet suck and swallow. Gradually, preemies will learn to eat small amounts of milk or formula by mouth, either through nursing or with a special bottle.

The Merck Manual has detailed facts about prematurity, with useful information on treatments in the NICU.

7. A Premature Baby Leaves the NICU When They Are Doing Well, Not When They Reach a Certain Age or Weight

Many doctors use a baby’s original due date as a target for a premature baby to go home from the hospital. There is no hard and fast rule, however. In general, babies can go home when their medical problems are under control, and they have reached all of these milestones:

• They are not having any pauses in their breathing, or other respiratory problems.
• They can maintain their own body temperature in a crib.
• They can eat normally, by the breast or bottle and are receiving the nutrition they need.
• They keep gaining weight.

Most preemies will have a “car seat challenge,” where doctors and nurses observe them in their car seat at the hospital, to make sure they can stay in that position without any problems before their first trip in a car.

8. A Premature Baby May Get Medicine and Other Special Care at Home After the NICU

When a preemie goes home, their doctor will keep close tabs on them. At first, they may need more frequent visits to the pediatrician than full-term babies do. 

Some premature babies will go home with special care like extra oxygen, tube feeding, or certain medicines. The doctors and nurses at the NICU and Special Care Nursery will make sure that parents are trained and confident in giving this special care at home before the baby is released.

9. The Causes of Prematurity Are not Fully Understood – This is What Makes a Premature Birth Unique

There are several conditions that can cause labor to start early, like infections, diabetes, preeclampsia, severe stress or exhaustion, and severe dehydration. But early labor can happen to many mothers who don’t have any of these problems.

There are also several known risk factors for preterm birth. This means that pregnant women with these characteristics have a higher chance of going into labor early. Risk factors are grouped into medical factors and lifestyle factors. 

Well-known medical risk factors for preterm labor include:

• Prior miscarriage
• Pregnancy with twins, triplets, or other multiples
• A family history of a mother, sister, or grandmother who had a preterm delivery
• Problems with the womb, placenta, or the cervix
• A pregnancy that started with in vitro fertilization (IVF)
• Being underweight or overweight before pregnancy

Some of the lifestyle factors that could increase a woman’s chance of premature labor include:

• High levels of stress
• Smoking
• Alcohol use

Even though researchers and doctors know about these risk factors, many cases of preterm birth happen in women with none of these. In fact, up to half of women who give birth early have no known risk factors⁶. 

10. There Are Steps You Can Take to Understand and Lower Your Risk of Preterm Labor

Although preterm labor can happen in healthy women with no risk factors, there are several things you can do to improve your chances of having a healthy delivery.

Most importantly, keep your pregnancy as healthy as possible. Keep up with prenatal visits to your doctor or midwife and follow their recommendations for a healthy pregnancy. Prenatal testing will help you and your doctor look out for any issues with your pregnancy.

There are also tools for understanding whether you have a higher risk of premature delivery. The PreTRM® Test for Risk Management is a simple blood test performed during weeks 18 through 20 of your pregnancy. It measures the levels of proteins circulating in the blood that signal a higher than average risk of preterm labor. When you take the PreTRM Test, your doctor will get a report that shows your pregnancy’s risk of preterm birth.

With a risk report from your PreTRM Test, you and your doctor will be able to understand your risk of delivering early and adjust your prenatal care as needed. 

For more information about strategies to prevent preterm birth and understanding your risk, check out our blog.

Additional Resources for Premature Baby Facts

We hope this article has been useful in presenting some of the most interesting facts about prematurity. To take a deeper dive into risk factors, consequences, and the latest science about preterm birth, explore all of our resources for Moms.

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2. Preventive Services Task Force. Screening for preeclampsia: U.S. Preventive Services Task Force recommendation statement. JAMA. 2017;317(16):1661–67.
3. Mai CT, et al. National population‐based estimates for major birth defects, 2010–2014. Birth Defects Research. 2019; 111(18): 1420-1435.
4. O’Sullivan BP, et al. Cystic fibrosis. Lancet. 2009;373(9678):1891–1904.
5. Callaghan WM, et al. The contribution of preterm birth to infant mortality rates in the United States. Pediatrics. 2006 Oct;118(4):1566-73.
6. Iams, JD, et al. Prevention of preterm parturition. N Engl J Med. 2014;370:254-61.