About the Data

To develop this tool, researchers used data from standardized assessments of nearly 5,000 preterm infants born at hospitals within the NICHD Neonatal Research Network (NRN) between 2006 and 2012.

NRN researchers then confirmed their findings using data from 51,000 infants born between 2006 and 2012, and 26,000 infants born between 2013 and 2016, at hospitals participating in the Vermont Oxford Network (VON) . VON is a nonprofit organization dedicated to improving the quality, safety, and value of care for newborn infants and their families through quality improvement, education, and research.

NRN researchers also used VON data to describe differences in survival across U.S. hospitals. Hospitals submit data to VON about infant care practices and outcomes, including for more than 85 percent of the extremely preterm infants born in the United States.

NRN research shows that considering factors in addition to gestational age provides a more accurate way to estimate infant outcomes than using gestational age alone.

These outcome data are based on five factors, including:

  • Gestational Age: Best obstetric estimate of completed weeks of gestation, from 22 weeks to 25 weeks, at birth. For example, “22 weeks” would refer to 22 weeks 0 days through 22 weeks 6 days postmenstrual age.
  • Birth Weight: From 401 grams to 1,000 grams, the weight range of the infants included in this sample
  • Infant Sex
  • Singleton Birth: Infants included in this sample were from singleton and multiple pregnancies (e.g., twins or triplets)
  • Antenatal Steroids: Whether the mother received any corticosteroids before birth to help the infant mature

The medical care that infants receive after birth also impacts infant outcomes. Different hospitals have different outcomes, which is why a range of hospital outcome rates is presented.

The data show the following outcomes:

  • Survival:
    Defined as either:

    • Survival to discharge from the Neonatal Intensive Care Unit (NICU), or
    • Survival to one year of age if still hospitalized

    The hospital range for survival (10th to 90th percentile) represents the extent of differences among U.S. hospitals participating in VON. The hospital rates are adjusted to account for smaller hospitals and hospitals with smaller numbers of births.

  • Profound Neurodevelopmental Impairment*: 
    Defined as either:
    • Bayley Scales of Infant and Toddler Development, third edition (BSID-III) cognitive composite score of “untestable,” or
    • Gross Motor Function Classification System (GMFCS) level of 5 (most impaired), which represents limited voluntary movement including an inability to lift the head against gravity
  • Moderate to Severe Neurodevelopmental Impairment*: 
    Defined as one or more of the following:
    • Cognitive developmental delay, defined as a BSID-III cognitive composite score less than 85 (i.e., more than 1 standard deviation below the standardized mean score of 100)
    • Moderate or severe cerebral palsy or GMFCS level of 2 to 5, which means that the infant has some degree of movement limitation
    • Legal blindness in both eyes (visual acuity <20/200), or
    • Severe hearing impairment that could not be corrected with amplification at both ears (the child is not considered impaired if able to follow spoken directions from the examiner)

* Evaluated at 18 to 26 months’ corrected age (that is, months from the infant’s due date)

Extremely preterm infants do not survive without active treatment, including support for breathing, nutrition, or specific organs, such as the heart. For this study, active treatment was defined as a breathing tube, surfactant therapy, epinephrine, chest compressions, ventilatory support (including continuous positive airway pressure, bag-valve-mask ventilation, or mechanical ventilation), or intravenous nutrition. Some infants may not benefit from active treatment.

The tool reports outcomes for actively treated infants and for all infants, including those who did not receive active treatment.

The following tables list average outcomes for the NRN sample for 2006 through 2012. They can be used for general reference, and to better understand differences between outcomes from individual hospitals and outcomes from NRN hospitals during the study.

Survival to Neonatal Intensive Care Unit (NICU) Discharge or 1 Year for Infants in the NRN

 Among Actively Treated Infants
Probability of Survival with Active Treatment*All Infants (n)Not Actively Treated (n)Actively Treated (n)Died on Day of Birth (n, %)Age of Death, in Days (median, 25th-75th percentile)**Remain Hospitalized at 1 year (n, %)Survived to Discharge or 1 Year (n, %)
≤5%6363 (100%)0N/AN/AN/A0 (0%)
6-10%284278 (98%)63 (50%)6 (3-18)0 (0%)0 (0%)
11-20%282192 (68%)9039 (43%)10 (3-24)1 (1%)9 (10%)
21-40%59673 (12%)523122 (23%)11 (4-23)3 (1%)155 (30%)
41-60%98812 (1%)976122 (13%)11 (4-24)6 (1%)478 (49%)
61-80%16012 (<0.1%)159972 (5%)17 (6-44)15 (1%)1173 (73%)
>80%9790 (0%)97928 (3%)18 (9-36)6 (1%)826 (84%)

*Estimated from the tool on this website
**Among infants who did not die on the day of birth

Follow-up Outcomes at 18 to 26 Months for Infants in the NRN

Probability of Survival with Active TreatmentProfound Neurodevelopmental Impairment (%)Moderate-Severe Neurodevelopmental Impairment (%)**Blindness (%)Deafness (%)Moderate-Severe Cerebral Palsy (%)Cognitive Developmental Delay (%)

* No infants survived to follow-up
** Includes infants with profound neurodevelopmental impairment

The data from this tool describe outcomes for large groups of infants at the time of birth. The tool should be used for infants within a few hours of birth; beyond that timeframe, other factors may better predict outcomes. The data represent the number of infants in a large group of similar infants that had each specific outcome. The tool cannot predict outcomes for any individual infant.

It is important to note that each infant is an individual, that rates of outcomes can change over time, and that they differ between hospitals. Several factors outside of those included here, such as differences in patient characteristics, obstetric care, NICU features and expertise, and care after discharge, may account for differences in outcomes.

The follow-up outcomes at 18 to 26 months’ corrected age provide a view of early life outcomes for children born extremely preterm. However, the data represent only a particular moment in time. Many factors, including those outside of the NICU, influence a child’s growth and development.

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