. Author manuscript; available in PMC: 2017 Feb 1.

Published in final edited form as: Am J Perinatol. 2016 Jan 22;33(3):318–328. doi: 10.1055/s-0035-1571202

Table 2. Characteristics of Select Cohort Studies Evaluating Long-term Outcomes for Extremely Preterm Infants.

Study (Country)	Follow-up	Details	Definition of moderate disability	Definition of severe disability
NICHD NRN¹⁷ (United States)	18-22 mo corrected age	Multicenter cohort evaluating 2630 (65%) of 4329 inborn live births receiving active treatment with survival to 18-22 corrected age.	Bayley-III cognitive or motor score 1-2 SD below mean, moderate CP, or a GMFCS level of 2 or 3.	Bayley-III cognitive or motor score >2 SD below mean, severe CP, GMFCS level of 4 or 5, bilateral blindness, or severe hearing impairment not corrected with bilateral amplification.
EXPRESS⁸³ (Sweden)	2.5 yr	Population-based cohort evaluating 491 (69%) of 707 live births surviving to 30mo corrected age.	Bayley-III score 2-3 SD below mean (any scales), moderate CP, moderate visual or hearing impairment.	Bayley-lll composite cognitive, language or motor score <3 SD below mean, severe CP, or bilateral blindness or deafness.
EPICure⁷⁸ (United Kingdom)	3 yr (range of 27-48 mo)	Population based cohort evaluating 584 (57%) of 1031 live births surviving to 3 yr. Age at assessment was variable, with use of multiple scales.	Ambulant CP (GMFCS 2), functionally impaired vision, hearing loss improved by aids, or a developmental score within 2-3 SD below mean.	Non-ambulant CP (GMFCS 3-5), blindness, profound sensorineural hearing loss not improved by aids, or a developmental quotient <3 SD below mean.

Abbreviations: Bayley-III, Bayley Scales of Infant and Toddler Development-3rd edition; SD, standard deviation; CP, cerebral palsy; GMFCS, Gross Motor Function Classification System.