Premature Birth and Survival Statistics

Birth weight and steroids affect a preemie's odds of survival

A premature baby in an incubator

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Many women, especially those who are anxious after a past pregnancy loss, breathe a sigh of relief after their pregnancy reaches the point at which the baby would be able to survive if born early. Pinpointing that date is complicated and many factors affect premature infant survival and the possibility of impairments or disabilities after birth.

Age of Viability

Strictly speaking, most doctors define the age of viability as being about 24 weeks of gestation. In many hospitals, 24 weeks is the cutoff point for when doctors will use intensive medical intervention to attempt to save the life of a baby born prematurely.

A baby born at 24 weeks would generally require a lot of intervention, potentially including mechanical ventilation and other invasive treatments followed by a lengthy stay in a neonatal intensive care unit (NICU), possibly also requiring tubal assistance with eating and breathing. In the hands of experienced specialists, babies born slightly earlier may have a chance at survival. Babies born at 23 weeks may survive in a state-of-the-art NICU, but the odds of survival are much lower. A 2015 study also showed that babies born at 22 weeks may have a small chance at survival, but death or serious health issues still have a higher probability of occurring.

The odds of survival increase as the pregnancy progresses, and even an extra week in the womb can make a difference. In general, premature babies born closer to 37 weeks will be better off than those born before 28 weeks.

Factors Affecting Survival

Multiple factors can play into whether or not a baby will survive premature birth, including the baby's birth weight. Low birth weight is independently linked to reduced odds of survival and a higher risk of disabilities and health problems.

In addition, if the early birth resulted from induction or C-section due to a medical condition, such as placental abruption or oxygen deprivation before the delivery, that condition can affect the baby's health and survival.

Another factor is whether the doctors had time before birth to treat the baby with steroids to speed up lung development. The mother gets the steroids, which then pass through the placenta to the fetus. A very premature baby treated with steroids before birth is more likely to survive than a baby born unexpectedly premature. The steroids can make a difference in whether or not the baby is able to breathe outside the womb.

It's also worthy to note that girls are more likely to survive very early premature birth, as are babies born in singleton rather than multiple pregnancies.

Survival Statistics

Based on information from the Quint Boenker Preemie Survival Foundation and the March of Dimes, below is the likelihood of survival for a baby born prematurely. It's important to note that these percentages are statistics and do not predict the survival of an individual baby.

Likelihood of Survival Based on Length of Pregnancy

23 weeks: 17%
24 weeks: 39%
25 weeks: 50%
26 weeks: 80%
27 weeks: 90%
28 to 31 weeks: 90 to 95%
32 to 33 weeks: 95%
34+ weeks: Almost as likely as a full-term baby

Risk of Disabilities

In addition to the risk of death, babies born very prematurely can face high odds of having some level of learning disabilities or other developmental impairment, but the severity of the disabilities or impairment can vary heavily. This can depend on many factors, including the need for and types of treatment received in the immediate neonatal period. The more intense treatment, sometimes the greater the risk factors for these extremely small and fragile babies. In essence, the very procedures that are life-saving also have the ability to limit babies' abilities as they grow up. It is nearly impossible to tell which babies will have problems and how severe these problems will be later in life.

For every 26-week baby, about 20% of them will have no long-term problems. That leaves about 80% with some form of developmental or physical problem in their lives.

About 34% of babies born at the 26-week mark will have a mild disability. A mild disability is defined as something like near-sightedness or minor cognitive impairment. Even within this category, you can see that there is a wide range of potential problems.

Twenty-four percent of babies born at the 26-week mark will have a moderate disability. A moderate disability includes problems such as visual/hearing impairment or cerebral palsy with the ability to walk. Cerebral palsy in and of itself can drastically vary from person to person. Early intervention can also help with preventing or lessening some of the symptoms.

The remaining 22% will have severe disabilities. This can include blindness or profound deafness. It can also include cerebral palsy with no ability to walk. This is typically what people think of when they consider developmental disabilities following a preterm birth.

Babies who are born early face the risk of learning disabilities and other problems, but the specific odds of these problems vary heavily depending on factors such as birth weight and whether or not there was oxygen deprivation before birth.

This is true even for babies who you would not necessarily categorize as preterm, including those born in the early term. The baby’s brain undergoes much growth and development in the last weeks of pregnancy.

If you expect to deliver an extremely premature baby, start a conversation with the doctors who will be caring for your baby about what type of resuscitation you would want for your baby at which gestational ages.

What to Discuss With Your Doctor

There is a wide range of possibilities that are very specific to the situation at hand. Questions to consider asking include:

  • What is the gestational age at which my baby was (or will be) born?
  • Was the baby oxygen-deprived prior to birth? What are the expected consequences of that? What tests were run to check the severity? 
  • What types of interventions have been used or will be used in my baby’s care? What are the risks and benefits of each of these treatments? What are the alternatives?
  • What problems should I watch for after discharge? In the first year? When my child starts school?
  • What type of follow-up will my baby need? Is there an early intervention program?

A Word From Verywell

Clearly, there is a lot to consider and discuss with your doctor when it comes to preterm birth. It is not merely a discussion of whether the baby survives the birth, but what the long-term outcomes for your baby are. If your baby was born prematurely or you expect your baby to be born prematurely, talk at length with your baby's doctor so you can be as prepared as possible.

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