Premature babies' survival rates and health outcomes

While your preemie or micropreemie may look tiny and fragile, a stay at the NICU will give them a fighting chance to thrive. Here's what you can expect depending on what week your baby is born.

preemie baby
Photo credit: Jill Lehmann Photography via Getty Images

What does it mean to be preterm?

Babies are preterm if they're born before your 37th week of pregnancy. Compare that to a full-term infant who's born between 39 weeks through the 40th week of pregnancy. About 1 in 10 babies in the U.S. were born premature in 2020, according to the Centers for Disease Control and Prevention. But those stats can be deceiving because the rate of preterm births among Black women is 14 percent, or almost twice that as White women (9 percent).

Doctors tend to group preemies into four main categories, depending on what week they were born. These categories range from extremely preterm (babies born before week 25) to late preterm (preemies born between 34 and 36 weeks). Premature babies are also grouped according to birth weight. Girl babies tend to be smaller than boys, no matter what week they're born, and if you have multiples, those babies each usually weigh less than singletons.

Advertisement | page continues below

Preemie babies, especially those born extremely early and at the lowest birth weight (under 2 or even 3 pounds), are at higher risk for health complications and disabilities. But luckily, there have been so many medical breakthroughs that preemies today have better chances of surviving and thriving than even 15 years ago. With good care in the hospital and at home, a preemie baby will grow up and live a full, healthy life – as a child and adult.

What is a micro preemie?

Micropreemie is the term doctors use for babies either born before the 26th week of pregnancy or weighing less than 1.75 pounds (28 ounces) at birth. Because they're so tiny and weigh so little, micropreemies are at greater risk than even a preemie baby for health issues and disabilities as they grow older. Still, hospitals are doing amazing things to take care of micropreemies – even those born super early – and making sure they have the best odds of overcoming their challenges.

How early can a baby be born and survive?

Usually, after week 22. It's rare that premature babies born before week 22 survive. But micropreemies born between 22 and 26 weeks will need lots of medical attention to prevent any lasting damage to their brains, lungs, and other organs. That's because babies continue to grow and develop right up until 39 weeks, so the longer your baby stays inside the womb, the better their health.

Even micropreemies have a fighting chance, though, thanks to technology and medical advances. In a study of roughly 11,000 extremely premature babies, those born at 22 weeks had a 28 percent survival rate, while those born at 23 weeks had a 55 percent survival rate. But the even better news in the study came when researchers looked at these babies at 2 years old. About half of these micropreemies (born between 22 and 26 weeks) had no or mild disabilities and another 29 percent had moderate ones. Only 21 percent of preemies had severe disabilities like cerebral palsy, blindness, or neurological delays.

Besides age, there are other factors that play a role in a baby's chances of survival. They include birth weight, gender (girls have a higher rate of survival), the mom's age and health, pregnancy or birth complications, whether the baby is a singleton or a multiple (single babies have a better rate of survival), and whether there are any genetic abnormalities.

Outlook for a baby born at 26 to 28 weeks

Average weight: 1 pound, 12 ounces (0.8 kg) to 2 pounds, 7 ounces (1.1 kg)

Average length: 13 inches (33 cm) to 14.4 inches (36.5 cm)

Advertisement | page continues below

Average head circumference: 9 inches (23 cm) to 10.2 inches (26 cm)

Known as: Extremely preterm babies

About 1.5 percent of preemies in this country are born this early. Between 80 and 90 percent of premature babies who reach 28 weeks gestation survive. And only 1 in 10 preemies born at 28 weeks have long-lasting health problems.

However, these extremely preterm babies are at a higher risk for medical complications and may face an extended stay in the neonatal intensive care unit (NICU).

Here's what to expect:

Advertisement | page continues below
  • Most extremely preterm babies weigh less than 3 pounds.
  • A preemie baby looks very different than a full-term one. Their skin is wrinkled and reddish-purple in color, and so thin that you can see the blood vessels underneath. Their face and body are covered in soft hair called lanugo. They look thin because they haven't had time to put on fat.
  • They can open their eyes for a little while, but they can't focus.
  • These preemies have little muscle tone, and most move very little.
  • Almost all require treatment with oxygen, surfactant, and mechanical assistance to help them breathe.
  • These babies are too immature to suck, swallow, and breathe at the same time, so they must be fed through a vein (intravenously) until they develop these skills.
  • They often can't yet cry (or you can't hear them due to the tube in their throat), and they sleep most of the day.

Outlook for a baby born at 28 to 32 weeks

Weight: Between 2 pounds, 3.3 ounces (1 kg) and 3 pounds, 15.5 ounces (1.8 kg)

Length: Between 14.1 inches (36 cm) and 16 1/2 inches (42 cm)

Head circumference: Between 9.8 inches (25 cm) and 11 1/2 inches (29.5 cm)

Known as: Very preterm

Advertisement | page continues below

About 1.5 percent of all babies arrive in this time period. Twins, triplets (or more) are 9 times more likely than singletons to be very premature. Babies born between these weeks have an excellent chance of staying alive, and 90 percent will have no or minimal long-term health or developmental problems.

Here's what to expect:

  • Very preterm babies look quite similar to babies born earlier, but they're usually larger.
  • They've lost most of the lanugo that covers their bodies and have more body fat.
  • Most require treatment with oxygen, surfactant, and mechanical assistance to help them breathe.
  • Some of these babies can be fed breast milk or formula through a tube threaded through their nose or mouth into the stomach, although others will need to be fed intravenously.
  • Some of these babies can cry. They move more, although their movements are jerky.
  • They can grasp a finger and turn their head from side to side.
  • These babies can blink and open their eyes, and they begin to stay awake and alert for short periods.

Outlook for a baby born at 32 to 34 weeks

Weight: Between 3 pounds, 12 ounces (1.7 kg) and 4 pounds, 14 ounces (2 kg)

Length: Between 16.5 inches (42 cm) and 17 1/2 inches (44 1/2 cm)

Advertisement | page continues below

Head circumference: Between 11.4 inches (29 cm) and 12 inches (31 cm)

Known as: Moderately preterm

About 1.5 percent of all babies arrive at this time, and about 95 percent of them survive. Moderately preterm babies are less likely than babies born earlier to develop serious disabilities resulting from premature birth, though they may have a higher risk than full-term babies for learning and behavioral problems.

Here's what to expect:

  • Moderately preterm babies look thinner and their skin more wrinkled than full-term babies.
  • They can sometimes breathe on their own, and many just need supplemental oxygen to help them breathe.
  • They can sometimes be breastfed or bottle-fed. However, those who have breathing difficulties will probably need tube feeding.
  • They can control their own body temperature, but may still need the incubator.
Advertisement | page continues below

Outlook for a baby born at 34 to just under 37 weeks

Weight: Between 5 pounds, 11 ounces (2 kg) and 6 pounds, 7 ounces (3 kg)

Length: Between 17 inches (44 cm) and 19 inches (48 cm)

Head circumference: Between 12 inches (31 cm) and 13 inches (33 cm)

Known as: Late preterm

The majority of preemie babies, or 7.4 percent, are born late preterm. Preemies born after 34 weeks have the same chance of being healthy as full-term babies. They're less likely to develop serious disabilities (especially compared to preemies and micropreemies) though they probably will hit developmental milestones later.

Advertisement | page continues below

Here's what to expect:

  • Late preterm babies may still look thinner than full-term babies.
  • Late preemie babies remain at higher risk than full-term ones for health issues, including breathing and feeding problems and jaundice. These problems are usually mild, and most babies make a quick recovery.
  • Most preemies are learning to breast- or bottle-feed, although some may need tube feeding for a brief time. And they need plenty of patience as they get the hang of it.
  • At around 36 weeks, babies have enough muscle tone to curl into a fetal position.
  • Late preemies can control their movements more, so they move more fluidly.
  • Some babies at this age are able to put their hands in their mouths for sucking.

Learn more:

Follow your baby's amazing development

BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies.

AAP. 2019. Caring for a premature baby: What parents need to know. American Academy of Pediatrics. a new window [Accessed April 2022]

ACOG. 2022. Extremely preterm birth. American College of Obstetricians and Gynecologists. a new window [Accessed April 2022]

CDC. 2021. Premature birth. Centers for Disease Control and Prevention. a new window [Accessed April 2022]

March of Dimes. 2019. Premature Babies. a new window [Accessed April 2022]

Stanford Children’s Health. 2022. Premature Babies Survival Rate is Climbing, Study Says. a new window [Accessed April 2022]

JAMA. 2022. Mortality, In-Hospital Morbidity, Care Practices, and 2-Year Outcomes for Extremely Preterm Infants in the US, 2013-2018 a new window [Accessed April 2022]

Mayo Clinic. Undated. Premature Birth. a new window [Accessed April 2022]

LifeBridge Health/Children’s Hospital at Sinai. Undated. Parenting Your Preemie in the NICU. a new window [Accessed April 2022]

University of Utah/Utah Health. Undated. When Is It Safe to Deliver Your Baby. a new window [Accessed April 2022]

Linda Rodgers

Linda Rodgers is a former magazine editor turned freelance writer who focuses on health and wellness.