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Updated: May 25, 2026
Assessment and Evaluation of the High Risk Neonate: The NICU Network Neurobehavioral Scale
Published on: August 25, 2014
Relationship between attrition and neurodevelopmental impairment rates in extremely preterm infants at 18 to 24
Ursula Guillén1, Sara DeMauro, Li Ma
1Division of Neonatology, The Children's Hospital of Philadelphia, PA 19104, USA.
Insights
High rates of infant neurodevelopmental impairment (NDI) may be overestimated due to loss to follow-up. Higher NDI and follow-up loss were observed in the US compared to other countries.
Area of Science:
- Neonatal research
- Developmental pediatrics
- Public health
Background:
- Infants born with extremely low birth weight (<1000 g) or extremely low gestational age (<28 weeks) are at high risk for neurodevelopmental impairment (NDI).
- Accurate assessment of NDI is crucial for understanding long-term outcomes and guiding interventions.
- Loss to follow-up in longitudinal studies can introduce bias and affect the reliability of reported outcome statistics.
Purpose of the Study:
- To evaluate the impact of loss to follow-up rates at 18–24 months on neurodevelopmental outcome statistics.
- To investigate the relationship between follow-up rates and the incidence of NDI in high-risk infants.
- To compare NDI and follow-up rates across different countries.
Main Methods:
- Systematic review of studies published between 2000 and 2010.
- Inclusion criteria: studies reporting outcomes for infants <1000 g birth weight or <28 weeks' gestational age born after 1990, with primary outcome and follow-up rates at 18–24 months.
- Databases searched: MEDLINE, EMBASE, PubMed, and Cochrane Library.
Main Results:
- Twenty of 43 publications reported follow-up rates (71.6%–100%) for 34,185 infants.
- Neurodevelopmental impairment (NDI) rates varied widely (12.4%–57.5%).
- Higher NDI rates significantly correlated with greater loss to follow-up (r²=0.38, P=.007). Higher rates of both NDI and follow-up loss were observed in the United States compared to other high-income countries (r²=0.70, P=.001).
Conclusions:
- Ascertainment bias may lead to overestimation of NDI in extremely low birth weight or gestational age survivors.
- Differences in population characteristics and healthcare systems may contribute to variations in attrition rates and NDI.
- Strategies to improve follow-up rates are essential for accurate reporting of neurodevelopmental outcomes in high-risk infant populations.
Objective:
To assess the effect of loss to follow-up rates at 18 to 24 months on neurodevelopmental outcome statistics for infants of less than 1000 g birth weight or less than 28 weeks' gestational age.
Data Sources:
MEDLINE, EMBASE, PubMed, and Cochrane Library databases (January 1, 2000, to June 30, 2010).
Study Selection:
We searched for studies reporting outcomes of infants of less than 1000 g birth weight or less than 28 weeks' gestational age who were born after 1990.
Main Exposure:
Eligible articles had to report the primary outcome and follow-up rates at 18 to 24 months.
Main Outcome:
Our primary composite outcome of neurodevelopmental impairment (NDI) was any of a mental developmental quotient 2 SDs below the mean, using the Bayley Scales of Infant Development II; cerebral palsy; visual impairment; or significant hearing impairment.
Results:
Of 43 publications describing outcomes at 18 to 24 months, 20 provided rates of follow-up, describing a total of 34,185 infants. The NDI rates ranged between 12.4% and 57.5%. Follow-up rates ranged between 71.6% and 100%. Higher rates of NDI were significantly correlated with greater loss to follow-up (r(2) = 0.38, P = .007). Higher rates of both NDI and loss to follow-up were seen in the United States compared with Canada, the United Kingdom, Finland, Denmark, Austria, Germany, and Australia (r(2) = 0.70, P = .001).
Conclusions:
Ascertainment bias may overestimate NDI in extremely low-birth-weight or extremely low-gestational-age survivors at 18 to 24 months. Alternatively, the characteristics of different populations and health systems may contribute to higher rates of attrition and higher rates of NDI.
